EP3109889A1 - Rotating anode - Google Patents

Abstract

The present invention relates to an X-ray rotary anode (10) which has a carrier body (14) and a focal path (16) formed on the carrier body (14). The carrier body (14) and the focal path (16) are produced by powder metallurgy in a composite, the carrier body (14) is formed from molybdenum or a molybdenum-based alloy, and the focal lane (16) is formed from tungsten or a tungsten-based alloy. In the case of the finally heat-treated x-ray rotary anode (10), at least one section of the focal track (16) is present in a non-recrystallized and / or in a partially recrystallized structure.

Description

The present invention relates to an X-ray rotary anode which has a carrier body and a focal path formed on the carrier body, wherein the carrier body and the focal path are produced by powder metallurgy in the composite, the carrier body is formed from molybdenum or a molybdenum-based alloy, and the focal track made of tungsten or a tungsten-based alloy is formed.

X-ray anodes are used in X-ray tubes to generate X-rays. In use, electrons are emitted from a cathode of the x-ray tube and accelerated in the form of a focused electron beam onto the rotated x-ray rotating anode. Much of the energy of the electron beam is converted into heat in the X-ray rotary anode, while a small portion is emitted as X-radiation. The locally released amounts of heat lead to a strong heating of the X-ray rotary anode and to high temperature gradients. This leads to a heavy load on the X-ray rotary anode. The rotation of the X-ray rotary anode counteracts overheating of the anode material.

Typically, X-ray rotary anodes have a carrier body and a coating formed on the carrier body, which is specially designed for the generation of X-rays and is referred to in the art as a focal path. The carrier body and the focal track are formed of refractory materials. As a rule, the focal track covers at least the region of the carrier body which is exposed to the electron beam during use. In particular, materials with a high atomic number, such as tungsten, tungsten-based alloys, in particular tungsten-rhenium alloys, etc., are used for the focal path. Among other things, the carrier body must ensure effective heat dissipation of the heat released at the point of impact of the electron beam. As suitable materials (with high thermal conductivity), in particular molybdenum, molybdenum-based alloys, etc., have been proven here. A proven and relatively inexpensive manufacturing process is powder metallurgy production, in which the carrier body and the focal track are produced in a composite.

For a high radiation yield or dose yield (to X-radiation) is essential that the surface of the focal track is as smooth as possible. With regard to the Long-term use and the achievable life of the focal point should be as stable as possible against a roughening of the focal point surface and the formation of wide and / or deep cracks in the same. Due to the high temperatures and temperature gradients as well as the high rotational speeds, relatively high thermal and mechanical stresses occur on the carrier body. Despite these stresses, the carrier body should be as stable as possible against macroscopic deformations. So far, the prevailing view has been that this stability can be obtained both in the focal lane and in the carrier body in that both the focal lane and the carrier body are present in a completely recrystallized structure. It was assumed that in this way the structure of the focal track as well as the structure of the support body are largely stable even with the high, occurring use temperatures against subsequent microstructural changes (eg compared to a recrystallization, etc.).

However, the recrystallization in the focal path, which takes place within the scope of previous powder-metallurgical production, leads to relatively large particle sizes. Such structures involve the risk of forming relatively deep and wide cracks which preferentially spread along the grain boundaries. Further, with large grain sizes, there is a greater tendency for relatively rough roughening of the focal surface to occur over the period of use. A recrystallized structure in the carrier body causes the strength and hardness thereof to be reduced. In particular, at high temperatures and high mechanical loads, a plastic deformation of the carrier body (in particular when the yield stress is exceeded) can occur. Particularly in the high-power range, in which a high dose rate (or radiation power) can be provided and the rotational speed of the x-ray rotary anode is comparatively high, these critical values are in part exceeded. Due to the reduced heat resistance of the (completely recrystallized) carrier body material, the possible uses of X-ray rotary anodes with completely recrystallized structure of the carrier body are accordingly limited. So far, for applications in which a high strength and hardness of the carrier body is required even at high temperatures, special alloys and / or materials, which atomic or particulate impurities are added to increase the strength used (see, eg US 2005/0135959 A1 ).

In the publication US Pat. No. 6,487,275 B1 is an X-ray rotary anode with a focal path of a Wofram-rhenium alloy described which has a grain size of 0.9 microns to 10 microns and in the context of a CVD coating method (CVD: chemical vapor deposition; German: Chemical vapor deposition) can be produced.

Accordingly, the object of the present invention is to provide a powder metallurgically produced in the composite X-ray rotary anode, which allows a high dose yield over long periods of use and has a long service life.

The object is achieved by an X-ray rotary anode according to claim 1. Advantageous developments of the invention are specified in the subclaims.

According to the present invention, there is provided an X-ray rotary anode comprising a support body and a focal path formed on the support body. In this case, the carrier body and the focal path are produced by powder metallurgy in a composite, the carrier body is formed from molybdenum or a molybdenum-based alloy, and the focal lane is formed from tungsten or a tungsten-based alloy. In the finally heat-treated x-ray rotary anode, at least a portion of the focal path is present in a non-recrystallized and / or in a partially recrystallized structure.

By having at least a portion of the focal lane in a non-recrystallized and / or partially recrystallized structure, this section does not show grain nucleation (in the case of a non-recrystallized structure) or significantly less than 100% grain remodeling resulting crystal grains (partially recrystallized structure) on. The remaining portion of this section is present in a forming structure, which is obtained in the powder metallurgy production by the forming step, in particular by the forging process. Overall, in the portion having the non-recrystallized and / or partially recrystallized structure, a very fine-grained structure (both large-angle grain boundary and wide-angle grain boundary portions and small-angle grain boundaries) having high strength and hardness is obtained. This structure has a very smooth surface, which is advantageous in terms of dose yield. It was found that this structure recrystallized locally under the influence of an electron beam (For example, when "conditioning" or "retraction" with the electron beam, and / or during use). The region in which recrystallization takes place is limited to the immediate vicinity of the path of the electron beam on the focal path and, depending on the thickness of the focal path, can extend down into the carrier body (and possibly into it). The refractory path then has in the recrystallized region an increased ductility, which is advantageous with regard to the prevention of cracking, and an increased thermal conductivity, which is advantageous with regard to an effective heat dissipation to the carrier body. The surrounding areas of the focal track remain largely unchanged. In particular, they are still present in a non-recrystallized and / or a partially recrystallized structure and accordingly have a high strength and hardness. This is advantageous in terms of stabilization of the recrystallized region of the focal path. Furthermore, it has surprisingly been found that the locally recrystallized structure of the focal track (in use) remains considerably finer grained than is the case in the recrystallization processes in the context of conventional production processes, in particular the conventional powder metallurgical production processes. The focal track surface is also smooth in the areas with the recrystallized structure over long periods of use and has a uniform, finely distributed crack pattern. Accordingly, with the X-ray rotary anode according to the invention over long periods of use a high dose yield can be achieved. Furthermore, it has a long service life. A possible explanation for the fine-grained formation of the recrystallized structure of the focal path under the action of the electron beam is that a shock-like transformation takes place by the action of the electron beam. In contrast, it has been found that in the heat treatment carried out in the context of conventional powder metallurgical production, even during heating in the furnace, until the holding temperature is reached, recovery processes take place which influence the recrystallization behavior.

With a certain composition of the focal track, a higher starting hardness (and a higher starting strength) can be obtained with increasing degree of deformation (which is set in the step of forming, in particular forging). From this starting hardness (and starting strength), the hardness (and strength) decreases with the degree of recrystallization of the structure. As the degree of recrystallization increases, ductility also increases. The preferred texturing of the <111> direction and the <001> direction perpendicular to FIG In particular, the focal plane is adjusted by the forging process (with a force acting substantially perpendicular to the focal plane). It has also been found that even this preferred texturing decreases with the degree of recrystallization of the structure. Corresponding relationships also apply to the carrier body. From these dependencies, the person skilled in the art recognizes how to select the parameters of the powder metallurgy production (in particular the temperature during forging, degree of deformation in the forging process, temperature during the heat treatment, duration of the heat treatment) in order to achieve the features specified in accordance with the invention to get at least a section of the focal track. In the present context, a partially recrystallized structure (with respect to the focal path and with respect to the carrier body) is understood to mean a structure in which grain grains formed by grain remodeling are surrounded by a forming structure and in which a cross-sectional area through the part Recrystallized structure these crystal grains form an area ratio in the range of 5-90%. If the area fraction of the crystal grains formed by grain regeneration is in the range below 5% or if there are no crystal grains formed in the structure by grain nucleation, an unrecrystallized structure is assumed in the present context. If the area fraction exceeds 90%, then in the present context a completely recrystallized structure is assumed. A possible measuring method suitable for determining the area fraction is described below in connection with the description of FIG Figs. 4A-4D specified.

The X-ray rotary anode according to the invention is, in particular, a high-performance X-ray rotary anode which is designed for high radiation power (or dose rate) and a high rotational speed. Such high-power X-ray rotary anodes are used in particular in the medical field, such as in computed tomography (CT) and in cardiovascular applications (CV). In general, further layers, add-on parts, etc., such as a graphite block, etc., may also be provided on the carrier body, in particular on the side remote from the focal point. In the case of high-performance x-ray rotary anodes, additional heat removal from the carrier body is generally required. In particular, the inventive X-ray rotary anode is designed for active cooling. In this case, immediately adjacent to or in the vicinity of the carrier body, in particular centrally through the x-ray rotary anode (for example, through one, along the Rotation symmetry axis extending channel), a flowing fluid out, which serves for heat dissipation from the carrier body. Alternatively, to increase the heat storage capacity of the x-ray rotary anode and to increase the heat radiation, a graphite body (eg by soldering, diffusion bonding, etc.) may be attached to the rear side of the carrier body. Alternatively, however, the X-ray rotary anode can also be designed for lower radiation powers. In this case, it may be possible to dispense with an active cooling and the attachment of a graphite block.

A molybdenum-based alloy is particularly referred to an alloy containing molybdenum as the main constituent, i. to a higher proportion (measured in weight percent) than any other containing element. In particular, special alloys with high strength and hardness can also be used as the carrier body material and / or atomic impurities or particles can be added to the respective carrier body material to increase the strength. According to a development, the molybdenum-based alloy has a proportion of at least 80 (wt.%: Weight percent) molybdenum, in particular of at least 98 wt.% Molybdenum. With a tungsten-based alloy is particularly referred to an alloy having tungsten as the main component. In particular, the focal track is formed from a tungsten-rhenium alloy having a rhenium content of up to 26 wt.%. In particular, the rhenium content is in a range of 5-10 wt.%. Good properties can be achieved with regard to hardness, temperature resistance and heat conduction in the case of these stated compositions of the focal track and of the carrier body and especially in the narrower regions specified in each case.

A "finally heat-treated x-ray rotary anode" is understood to have passed through all the heat treatment (s) carried out during the powder metallurgical production. The claimed features (and also the features explained below with reference to the subclaims and variants) relate in particular to the end product (not yet used), as it is present after completion of the heat treatment (s) carried out as part of the powder metallurgical production , The powder metallurgy production of the carrier body and the fuel track in the composite can be seen on the end product, inter alia, at the pronounced diffusion zone between the carrier body and the focal track. In alternative manufacturing processes, such as CVD deposition of the focal track (CVD: chemical vapor deposition) or by means of vacuum plasma spraying, the diffusion zone is typically formed smaller or almost nonexistent. Specifically, the "section" of the focal path is referred to a macroscopic contiguous section (ie, including a plurality of grain boundaries and / or grain boundary sections) of the focal path. It can also be several, such sections with the claimed properties. In particular, the portion of the focal path over which (in use) the path of the electron beam passes has the claimed properties. In particular, the focal track over its entire area on the claimed properties. A "non-recrystallized and / or partially recrystallized structure" refers to a structure which can not be exclusively recrystallized, which can be exclusively partially recrystallized, or which can not be partially recrystallized in sections and partially recrystallized in sections.

wobei I_(hkl) die gemessene Intensität des Peaks (hkl) ist, I°_(hkl) die texturfreie Intensität des Peaks (hkl) gemäß der JCPDS-Datenbank ist, und n die Anzahl der ausgewerteten Peaks ist, wobei die nachfolgenden Peaks ausgewertet wurden: (110), (200), (211), (220), (310), (222), und (321)). Dementsprechend sind in der Brennbahn die <111>-Richtung und die <001>-Richtung stärker entlang der Normalen der Brennbahn-Ebene ausgerichtet als entlang der Richtungen parallel zu der Brennbahn-Ebene. Die "Brennbahn-Ebene" wird dabei durch die Haupterstreckungsfläche der Brennbahn bestimmt. Ist die Brennbahn-Ebene gekrümmt (was beispielsweise bei einer kegelstumpfförmig verlaufenden Brennbahn der Fall ist), so wird auf die, in dem jeweiligen Mess- oder Bezugspunkt der Brennbahn vorliegende Haupterstreckungsfläche derselben Bezug genommen.According to a further development, the section of the focal track perpendicular to a focal plane has preferred texturing of the <111> -direction with a texture coefficient TC ₍₂₂₂₎ of ≥ 4 determinable by X-ray diffraction (XRD: X-ray diffraction) and a preferred Texturing of the <001> -direction with an X-ray diffraction determinable texture coefficient TC ₍₂₀₀₎ of ≥ 5 on (with $${\mathit{TC}}_{\left(\mathit{hkl}\right)}=\frac{\frac{I_{\left(\mathit{hkl}\right)}}{\underset{j=1}{\overset{n}{\Sigma }}{I}_{j\left(\mathit{hkl}\right)}}}{\frac{I_{\left(\mathit{hkl}\right)}^0}{\frac{\underset{j=1}{\overset{n}{\Sigma }}{I}_{j\left(\mathit{hkl}\right)}^0}{\underset{j=1}{\overset{n}{\Sigma }}{I}_{j\left(\mathit{hkl}\right)}^0}}}$$

where I _{(hkl) is} the measured intensity of the peak (hkl), I ° _{(hkl) is} the texture-free intensity of the peak (hkl) according to the JCPDS database, and n is the number of evaluated peaks, with the subsequent peaks being evaluated : (110), (200), (211), (220), (310), (222), and (321)). Accordingly, in the focal path, the <111> direction and the <001> direction are aligned more along the normal of the focal plane than along the directions parallel to the focal plane. The "focal plane" is determined by the main extension surface of the focal track. If the focal plane is curved (which is the case, for example, in the case of a frustum-shaped focal path), reference is made to the main extension surface present in the respective measuring or reference point of the focal track.

As explained above, the preferential texturing of the <111> direction and the <001> direction perpendicular to the focal plane is set by the forging process and decreases with increasing degree of recrystallization of the focal path. The degree of recrystallization in turn increases with increasing temperature and with increasing duration of the heat treatment (at and / or after forging). Accordingly, the stated texture coefficients are also a measure of the degree of recrystallization of the focal track. In particular, the higher the texture coefficients of these directions, the lower the degree of recrystallization of the focal track. Within the ranges of the texture coefficients specified according to this development, the section of the focal track is present in a non-recrystallized structure or in a partially recrystallized structure with a relatively low degree of recrystallization. It was found that within these ranges, the above-explained, advantageous properties (high hardness, fine graininess) of the focal path can be achieved, with these advantageous properties occur even more at even higher texture coefficients. According to a further development, the section of the focal track perpendicular to the focal plane has a texture coefficient TC ₍₂₂₂₎ of ≥ 5 and / or a texture coefficient TC ₍₂₀₀₎ of ≥ 6. If the degree of deformation is lower (for example only in the range of 20% -30% (total) degree of deformation of the x-ray rotary anode), then the preferred texturisations given above are also less pronounced. According to a further development, the section of the focal track perpendicular to the focal plane has a texture coefficient TC ₍₂₂₂₎ of ≥ 3.3 and / or a texture coefficient TC ₍₂₀₀₎ of ≥ 4, the range of these lower limit values in particular at comparatively low degrees of deformation is approximated.

Tungsten and tungsten based alloys have a cubic internal centered crystal structure. The directions in the square brackets <...> also refer to the equivalent directions. For example, in addition to the [001] direction, the <001> direction also includes the directions [001], [010], [002], [200], and [100] (with respect to a cubic-centered unit cell, respectively). The parenthesized symbols (...) are used to denote lattice planes. The peaks evaluated in the XRD measurement are each designated with the associated network levels (for example, (222)). Again, it should be noted that, as is known in the art, the peak that can be evaluated as part of the XRD measurement at the network level (222) is also weighted by the equivalent network levels (eg, (111), etc.). Accordingly, the intensity of the peak determined by XRD measurement (222) and in particular the thereof texture coefficient TC _{(222) determined} a measure of the preferential texturing of the <111> direction (perpendicular to the focal plane). Similarly, the intensity of the peak (200) determined by XRD measurement, and in particular the texture coefficient TC ₍₂₀₀₎ determined therefrom, is a measure of the preferential texturing of the <001> direction.

The texture coefficient was calculated according to the following formula: $${\mathit{TC}}_{\left(\mathit{hkl}\right)}=\frac{\frac{I_{\left(\mathit{hkl}\right)}}{\underset{i=1}{\overset{n}{\Sigma }}{I}_j\left(\mathit{hkl}\right)}}{\frac{I_{\left(\mathit{hkl}\right)}^0}{\underset{j=1}{\overset{n}{\Sigma }}{I}_{j\left(\mathit{hkl}\right)}^0}}z\mathrm{,}\mathrm{B}\mathrm{,}f\ddot{\mathrm{u}}{\mathrm{r\; TC}}_{\left(222\right)}:{\mathit{TC}}_{\left(222\right)}=\frac{\frac{I_{\left(222\right)}}{\underset{j=1}{\overset{n}{\Sigma }}{I}_{j\left(\mathit{hkl}\right)}}}{\frac{I_{\left(222\right)}^0}{\underset{j=1}{\overset{n}{\Sigma }}{I}_{j\left(\mathit{hkl}\right)}^0}}$$

In this case, I _(hkl) denotes the intensity, determined by XRD measurement, of the relevant peak (hkl) at which the texture coefficient TC _{(hkl) is} to be determined. The "specific intensity" of a peak (hkl) is the maximum of the relevant peak (hkl), as recorded in the XRD measurement. In the determination of the respective texture coefficient TC _(hkl) , in the sum of I _{j (hkl)} from j = 1 to n, the following intensities of the peaks (110), (200), (211), (XRD) are determined. 220), (310), (222), and (321) (ie: n = 7). I ° _(hkl) denotes the (normally normalized) texture-free intensity of the relevant peak (hkl) at which the texture coefficient TC _{(hkl) is} to be determined. This texture-free intensity would be present if the material in question has no texturing. In a corresponding way, the sum of the texture-free intensities of these seven peaks is summed up in the sum over I ° _{j (hkl)} from j = 1 to n. The texture-free intensities for the respective peaks can be taken from databases, with the data in each case being used for the main constituent of the relevant material. Accordingly, in the present case, the powder diffraction file for tungsten (JCPDS No. 00-004-0806) was used for the focal line. In particular, for the peak (110) the texture-free intensity 100, for the peak (200) the texture-free intensity 15, for the peak (211) the texture-free intensity 23, for the peak (220) the texture-free intensity 8, for the peak ( 310) uses the texture-free intensity 11, for the peak (222) the texture-free intensity 4 and for the peak (321) the texture-free intensity 18.

Hereinafter, a sample preparation and a measuring method used herein will be described for determining the intensities of the various peaks by X-ray diffraction. First, the track is ground so that the area of the forging zone (upper portion of the track which was in direct contact with the forging tool or in close proximity to the forging tool during the forging process) is removed, if not already complete in the finished X-ray rotary anode was removed. In particular, the focal track with a ground plane parallel to the focal plane is ground to a residual thickness of 0.1-0.5 mm (depending on the output thickness of the focal track). Subsequently, the obtained ground surface is electropolished several times, at least twice (to remove the deformation structure due to the grinding process). While performing the XRD measurement, the sample was rotated and excited to diffract over an area about 10 mm in diameter. To perform the XRD measurement, a theta-2 theta diffraction geometry is used. In the present case, the diffracted intensities were measured in an overview recording with 0.020 ° increment and with 2 seconds measurement time per measured angle. As X-ray radiation, Cu-Kα1 radiation having a wavelength of 1.5406 Å was used. The additional effects that occur due to the additional Cu-Kα2 radiation present in the obtained image were eliminated by an appropriate software. Subsequently, the maxima of the peaks are determined to the seven peaks specified above. In the present case, the XRD measurements were carried out with a Bruker axs Bragg Brentano diffractometer "D4 Endeaver" with a theta-2 theta diffraction geometry, a Göbel mirror and a Sol-X detector. However, as known in the art, another device may be used with appropriate settings such that comparable results are achieved.

Molybdenum and molybdenum based alloys also have a cubic internal centered crystal structure. Accordingly, the notations discussed above with respect to the focal path, the texture coefficient determination formula, the sample preparation, and the measurement method are respectively applicable. In the context of the sample preparation, in contrast to the method explained above, the X-ray rotary anode is ground down to the carrier body material, the ground surface extending parallel to the focal plane. For the texture-free intensities in the support body, the Powder Diffraction File for molybdenum (JCPDS No. 00-042-1120) was used. In particular, for the peak (110), the texture-free Intensity 100, for the peak (200) the texture-free intensity 16, for the peak (211) the texture-free intensity 31, for the peak (220) the texture-free intensity 9, for the peak (310) the texture-free intensity 14, for the peak (222) the texture-free intensity 3 and for the peak (321) the texture-free intensity 24 is used. -

According to a further development, the following relationship of the X-ray diffraction determinable texture coefficients TC ₍₂₂₂₎ and TC _{(310) is} fulfilled in the section of the focal track perpendicular to the focal plane. $$\frac{{\mathit{TC}}_{\left(222\right)}}{{\mathit{TC}}_{\left(310\right)}}\ge \mathrm{5th}$$

This ratio describes how much the peak (222) is broadened or smeared out. If the peak (222) is heavily smeared out, this also increases the intensity of the (adjacent) peak (310) and thus reduces the value of the ratio. Accordingly, the larger the ratio, the less severely the peak (222) is smeared out. It has been found that in the inventive X-ray rotary anodes in which the section of the focal track is present in a non-recrystallized and / or in a partially recrystallized structure, this ratio is significantly higher than in conventional powder metallurgically produced in combination X-ray rotary anodes. In particular, this ratio decreases with increasing degree of recrystallization. Accordingly, this ratio is a characteristic of the focal length, wherein at higher values of this ratio, the above-described, preferred properties (fine grain, low roughening) of the focal path are present in particular. In particular, this ratio is ≥ 7. At low degree of deformation, however, this ratio may also have a value lower than 5. In particular, this ratio is ≥ 4 or ≥ 3.5, the range of these lower limit values being achieved in particular in the case of low-conversion x-ray rotary anodes (for example with a (total) degree of deformation in the range of 20-30%). Nevertheless, these lower limits are higher than conventional X-ray anodes produced by powder metallurgy in a composite.

According to a development, the section of the focal track has a hardness of ≥ 350 HV 30. As explained above, such high hardness is particularly advantageous with respect to avoiding roughening and / or deformation of the focal track over its service life. In the, made in the context of this description Hardness data is in each case referred to a hardness determination according to DIN EN ISO 6507-1, wherein in particular a load application time of 2 seconds (according to DIN EN ISO 6507-1: 2 to 8 seconds) and an exposure time or load holding time of 10 seconds (according to DIN EN ISO 6507-1: 10 to 15 seconds). A deviation from this load application time and exposure time can affect the measured value obtained, in particular in the case of molybdenum and molybdenum-based alloys. The hardness measurement (both in the focal path and in the carrier body) is carried out in particular on a radial, perpendicular to the focal plane plane extending cross-sectional area of the X-ray rotary anode.

According to a further development, the section of the focal track is completely in a partially recrystallized structure. In particular, the entire focal track is completely in a partially recrystallized structure. According to a further development, crystal grains formed in the partially recrystallized structure by grain regeneration are surrounded by a forming structure and these crystal grains have an area fraction in the range of 10% to 80%, in particular in a range of 10%, based on a cross-sectional area through the partially recrystallized structure 20% to 60%. Within these areas, and in particular within the narrower range, it was possible to achieve good properties of the focal track with respect to its surface quality and dose yield, even over long periods of use. The method for determining the area ratio which can be used for the specified range of values is explained with reference to the figures (see in particular the description of the figures relating to FIGS FIGS. 4A-4D ). As an alternative to the developments explained above, provision can also be made for the section or possibly also the entire focal track to be present in a non-recrystallized structure. According to a further development, it is generally provided (irrespective of whether the section is present in a partially recrystallized and / or in a non-recrystallized structure) that the area fraction (the crystal grains produced by grain regeneration) is ≦ 80%, in particular ≦ 60%.

According to a development, the section of the focal track has a mean small-angle grain boundary distance of ≦ 10 μm. Here, the average small-angle grain boundary distance can be determined by a measuring method in which at a radial, perpendicular to the focal plane plane cross-sectional area in a region of the section of the focal path grain boundaries, grain boundary sections and Small-angle grain boundaries with a grain boundary angle of ≥ 5 ° are determined for determining the average small-angle grain boundary distance parallel to the focal plane in the resulting grain boundary pattern, a parallel to the cross-sectional area line of each parallel to the focal plane extending lines, each having a distance of 17.2 microns, is placed on each line, the distances between each two mutually adjacent intersections of the respective line with lines of the grain boundary pattern are determined and the average of these distances as a mean small-angle grain boundary distance parallel is determined to the focal plane, for determining the mean small-angle grain boundary distance perpendicular to the focal plane in the obtained grain boundary pattern, a parallel to the cross-sectional area extending line of each perpendicular to the focal plane extending lines, di e each have a distance of 17.2 microns, is placed, at the individual lines in each case the distances between each two mutually adjacent intersections of the respective line with lines of the grain boundary pattern are determined and the average of these distances as a mean small-angle grain boundary distance perpendicular is determined to the focal plane, and the average small angle grain boundary distance is determined as the geometric mean of the mean small angle grain boundary distance parallel to the focal plane and the mean small angle grain boundary distance perpendicular to the focal plane. Further details on the implementation of the measuring method are in the description of the Fig. 4A - 4D specified. Such a fine-grained structure, which has an average small-angle grain boundary distance of ≦ 10 μm, is particularly advantageous with regard to avoiding roughening of the focal point surface. This fine granularity of the structure also depends on the degree of deformation. Accordingly, especially at a high degree of deformation of the X-ray rotary anode, a low, medium small angle grain boundary distance can be achieved. In particular, the average small-angle grain boundary distance according to a development ≦ 5 microns. At a low degree of deformation of the X-ray rotary anode, the small angle grain boundary distance is slightly higher. In particular, according to a further development, it is ≦ 15 μm, whereby even this higher limit value is even lower than the corresponding value in conventional X-ray rotary anodes produced by powder metallurgy in a composite.

A characteristic variable for whether and to what extent a substructure is present is the ratio of the mean (large angle) grain boundary distance (ie, grain boundary angle of ≥ 15 °) to the mean (small angle) grain boundary distance (ie, grain boundary angle of ≥ 5 °). The higher this ratio, the lower the degree of recrystallization. According to a development, this ratio is ≥ 1.2. In particular, the ratio of ≥ 1.5, more preferably ≥ 2.

According to a development, the section of the focal path in directions parallel to the focal plane has a preferred texturing of the <101> direction. In this case, the higher the preferential texturing of the <101> direction in these directions parallel to the focal plane, the lower the degree of recrystallization of the focal track. The ratio of the preferential texturing of the <101> direction in the directions parallel to the focal plane with respect to the preferential texturing of the <111> direction and the <001> direction may be determined by EBSD analysis (EBSD: Electron Backscatter diffraction). Through the EBSD analysis, preferential texturing and EBSD texture coefficients can be determined both in directions parallel to the focal plane and perpendicular to the focal plane, with only one sample surface (eg, a cross-sectional area as shown in FIG Fig. 3 is shown) must be examined. The sample preparation and the measuring method are generally described with reference to Fig. 4A - 4D The details for determining the EBSD texture coefficient (in particular the exact processing of the measured values) are not discussed. Even without specifying the exact determination method of the EBSD texture coefficients, it is possible to obtain information about the characteristics of the preferred texturing in the different directions (perpendicular as well as parallel to the focal plane) from the comparison of the different EBSD texture coefficients. In this case, an EBSD texture coefficient of 5.5 was determined for a sample according to the invention perpendicular to the focal plane plane for the <111> direction and an EBSD texture coefficient of 5.5 for the <001> direction. Parallel to the focal plane, this EBSD texture coefficient of 2.5 in the radial direction (RD) for the <110> direction and an EBSD texture coefficient in the tangential direction (TD) for the <110> direction determined by 2.2. Accordingly, it may be noted that the preferential texturing of the <110> direction (or <101> direction) in directions parallel to the focal plane is less pronounced, in particular less than half as pronounced as the preference Textures of the <111> direction and the <001> direction perpendicular to the focal plane (this was confirmed by further samples).

According to a development, the focal track has a thickness (measured perpendicular to the focal plane) in the range of 0.5 mm to 1.5 mm. In use, in particular, a thickness in the range of about 1 mm has been proven. According to a development, the focal length and / or the carrier body has a relative density of ≥ 96%, in particular of ≥ 98%, (relative to the theoretical density), which is particularly advantageous with regard to the material properties and the heat conduction. The density measurement is carried out in particular according to DIN ISO 3369.

According to a further development (in the finally heat-treated x-ray rotary anode), at least one section of the carrier body is present in a non-recrystallized and / or in a partially recrystallized structure. It has been found that a carrier body with these features has a high stability against macroscopic deformations in comparison with carrier bodies with a recrystallized structure, in particular under high mechanical loads. Such carrier bodies are particularly well-suited for actively cooled X-ray rotary anodes, in which the temperature of the carrier body (or at least large portions thereof) can be kept within a range below the recrystallization threshold due to the active cooling. Furthermore, such carrier bodies are also very well suited for lower ranges of radiant power (so-called mid and low end range). If a graphite body is to be attached to the back of the support body, it is preferably mounted (for example by means of diffusion bonding) in such a way that heating of the support body (or parts thereof) via its recrystallization threshold is avoided. Because, according to the present invention, the focal path is present at least in sections in a non-recrystallised and / or partially recrystallized structure, the carrier body can also be inexpensively and simply in a non-recrystallized and / or in a partially recrystallized manner within the scope of powder metallurgical production. recrystallized structure are produced. According to a development, the section of the carrier body has a hardness of ≥ 230 HV 10, in particular of ≥ 260 HV 10. These regions are advantageous in terms of high stability of the carrier body against macroscopic deformations, wherein in the region of higher hardness is given a particularly high stability.

Accordingly, as described above with respect to the focal path, there are also interdependencies in hardness, degree of deformation, degree of recrystallization, and in the support body (in a given composition thereof) Ductility. From these dependencies it results for a person skilled in the art how to choose the parameters of the powder metallurgical production (in particular the temperature during forging, degree of deformation in the forging process, temperature during the heat treatment, duration of the heat treatment) for the respective composition of the carrier body Reference to the carrier body specified characteristics in at least a portion of the same. By "section" of the carrier body, reference is in particular made to a macroscopic coherent section (ie comprising a plurality of grain boundaries and / or grain boundary sections) of the carrier body. It can also be several, such sections with the claimed properties. In particular, the carrier body has over its entire area the respective claimed properties.

Another advantage of this development is that classic materials and material combinations can be used for the carrier body, which is particularly advantageous in terms of the manufacturing cost and cost. The use of special alloys and / or the addition of atomic impurities or particles to the carrier body material to increase its hardness and strength is / are not required. According to a development, the carrier body is formed from a molybdenum-based alloy whose other alloy constituents (apart from impurities by, for example, oxygen) are at least one element of the group Ti (Ti: titanium), Zr (Zr: zirconium), Hf (Hf: hafnium ) and by at least one element of the group C (C: carbon), N (N: nitrogen) are formed. The oxygen content should always be as low as possible. According to a further development, the carrier body material is formed by a molybdenum alloy designated as TZM, which is specified in the standard ASTM B387-90 for powder metallurgy production. In particular, the TZM alloy has a Ti content (Ti: titanium) of 0.40-0.55 wt%, a Zr content of 0.06-0.12 wt% (Zr: zirconium), a C Content of 0.010-0.040 wt% (C: carbon), an O content of less than 0.03 wt% (O: oxygen), and the remaining content (other than impurities) Mo (Mo: molybdenum) , According to a development, the carrier body material is formed by a molybdenum alloy which has an Hf content of 1.0 to 1.3% by weight (Hf: hafnium), a C content of 0.05-0.12% by weight. , an O content of less than 0.06 wt.% and the remainder (other than impurities) of molybdenum (this alloy is sometimes referred to as MHC). Both compositions produce oxygen an impurity whose proportion is to be kept as low as possible. The compositions mentioned have proven themselves very well with regard to good heat conduction and handling during production.

According to a development, the section of the carrier body perpendicular to the focal plane has a preferred texturing of the <111> direction and the <001> direction. According to a development, the section of the carrier body in directions parallel to the focal plane has a preferred texturing of the <101> direction. The specified preferred texturing will be adjusted accordingly in the forging process, as explained above with respect to the focal path. They are reduced again with increasing degree of recrystallization. From these dependencies results in turn for a person skilled in the art (in accordance with what has been explained above with respect to the focal path) how he has to select the parameters of the powder metallurgy production in the respective composition of the carrier body by the specified preferential texturing in at least one section of the carrier body to obtain. According to a development, the section of the carrier body perpendicular to the focal plane has a preferential texturing of the <111> direction with an X-ray diffraction determinable texture coefficient TC ₍₂₂₂₎ of ≥ 5 and the <001> direction with one, via X-ray diffraction determinable texture coefficients TC ₍₂₀₀₎ of ≥ 5. According to a further development, these texture coefficients TC ₍₂₂₂₎ and TC _{(200) are} each at least ≥ 4 (the range can be achieved directly above this low limit, in particular at a low degree of deformation). With regard to a high hardness and stability of the carrier body, a low degree of recrystallization and, accordingly, a high degree of preferred texturing is advantageous. Accordingly, according to a development, the texture coefficients TC ₍₂₂₂₎ and TC _{(200) are} each at least ≥ 5.5.

In the forging process, the force is applied substantially perpendicular to the focal plane. During the manufacturing process, this direction of the force action is usually substantially parallel to the (future) rotational axis of symmetry of the X-ray rotary anode. If the focal plane is substantially planar, this symmetry is maintained. On the other hand, if the focal plane is not flat, it is frustoconical, for example (cf. Fig. 3 ), so usually after or within the context of the forging process, the outer, circumferential portion is bent by a desired angle (eg in the range of 8 ° -12 °). The during the Forge set texture of the focal track and the carrier body is retained. Accordingly, with respect to the texture of the carrier body further reference is made to the focal plane (or to the interface between the focal path and carrier body). Due to the described change in shape in the case of an angled focal path, the texture of the carrier body may differ slightly in a central region (in a central region, then, instead of the focal plane, a plane perpendicular to the rotational axis of symmetry is decisive).

According to a development, the section of the carrier body at room temperature has an elongation at break of ≥ 2.5%. In particular, the section of the carrier body at room temperature has an elongation at break of ≥ 5%. In the case of elongation at break, it must again be taken into consideration that with increasing degree of recrystallization of the carrier body, its ductility and thus its elongation at break at room temperature increases. Because of this dependency, the person skilled in the art can accordingly select the parameters of powder metallurgy production (in particular the duration and temperature of the heat treatment (s)), so that the respective value ranges of the elongation at break are achieved. The measurement method associated with the elongation at break is to be carried out in accordance with DIN EN ISO 6892-1, wherein in each case a sample extending radially in the carrier body is used as the measuring sample. In particular, method B, which is based on the voltage velocity and described in DIN EN ISO 6892-1, should be used.

The present invention further relates to a use of an inventive X-ray rotary anode, which may optionally be formed according to one or more, the above-explained developments and / or variants, in an X-ray tube for generating X-radiation.

1. A) Bereitstellen eines durch Pressen und Sintern von entsprechenden Ausgangspulvern im Verbund hergestellten Ausgangs-Körpers mit einem Trägerkörper-Abschnitt aus Molybdän oder einer Molybdän-basierten Mischung und einem, auf dem Trägerkörper-Abschnitt ausgebildeten Brennbahn-Abschnitt aus Wolfram oder einer Wolfram-basierten Mischung;
2. B) Schmieden des Körpers; und
3. C) Durchführen einer Wärmebehandlung des Körpers bei und/oder nach dem Schritt des Schmiedens;

wobei die Wärmebehandlung bei derart niedrigen Temperaturen und über eine derartige Zeitdauer durchgeführt wird, dass bei der abschließend wärmebehandelten Röntgendrehanode zumindest ein Abschnitt der aus dem Brennbahn-Abschnitt erhaltenen Brennbahn in einer nicht rekristallisierten und/oder in einer teil-rekristallisierten Struktur vorliegt. Das Pressen und Sintern erfolgt dabei derart, dass ein dichter und homogener Sinterling (nachfolgend: Körper) erhalten wird (wie es in dem Fachgebiet bekannt ist). Der Sinterling weist insbesondere eine relative Dichte von ≥ 94 % (bezogen auf die theoretische Dichte) auf. Die oberhalb erläuterte, erfindungsgemäße Röntgendrehanode ist insbesondere durch das angegebene Herstellungsverfahren erhältlich. Das Verfahren kann dabei auch noch weitere Schritte aufweisen. Insbesondere kann vorgesehen sein, dass die Schritte des Schmiedens und der Wärmebehandlung mehrmals in Folge durchlaufen werden. Die letzte Wärmebehandlung kann insbesondere im Vakuum durchgeführt werden. Gemäß einer Weiterbildung ist vorgesehen, dass das Schmieden bei erhöhten Temperaturen durchgeführt wird, um den Umformwiderstand des Materials ausreichend abzusenken, und dass im Anschluss an den Schmiedevorgang zusätzlich eine Wärmebehandlung (Spannungsarmglühen) durchgeführt wird.The present invention further relates to a method for producing an X-ray rotary anode according to the invention, which is optionally formed according to one or more of the developments and / or variants described above, the method having the following steps:

1. A) providing an output body made by pressing and sintering respective starting powders in composite with a carrier body portion of molybdenum or a molybdenum-based mixture and one on which Carrier section formed focal track section of tungsten or a tungsten-based mixture;
2. B) forging the body; and
3. C) performing a heat treatment of the body at and / or after the forging step;

wherein the heat treatment is performed at such low temperatures and for such a period of time that in the finally heat treated X-ray rotary anode at least a portion of the focal path obtained from the focal section is in a non-recrystallized and / or partially recrystallized structure. The pressing and sintering is carried out in such a way that a dense and homogeneous sintered body (hereinafter: body) is obtained (as is known in the art). In particular, the sintered compact has a relative density of ≥ 94% (based on the theoretical density). The above-explained, inventive X-ray rotary anode is obtainable in particular by the specified production method. The method can also have additional steps. In particular, it can be provided that the steps of forging and heat treatment are passed through several times in succession. The last heat treatment can be carried out in particular in a vacuum. According to a further development, it is provided that the forging is carried out at elevated temperatures in order to lower the deformation resistance of the material sufficiently, and that, in addition to the forging process, a heat treatment (stress relief annealing) is additionally carried out.

According to a development, the heat treatment (during forging and / or during a forging process subsequent heat treatment) takes place at temperatures below the recrystallization temperature of the focal path, in particular at temperatures in the region of the recrystallization threshold of the focal path. According to a development, the heat treatment (during forging and / or during a forging process subsequent heat treatment) takes place at temperatures below the recrystallization temperature of the carrier body, in particular at temperatures in the region of the recrystallization threshold of the carrier body. The recrystallization temperature depends inter alia on the particular (material) composition and on the degree of deformation of the respective material. The higher the degree of deformation, the lower the recrystallization temperature. Depending on the shape of the X-ray rotary anode, regions of different degrees of deformation may also exist. According to a development, the Heat treatment at temperatures ≤ 1,500 ° C, in particular carried out at temperatures in a range of 1300-1500 ° C. These temperatures are particularly suitable for a carrier body made of TZM or from the above specified, concrete composition of Mo, Hf, C and O, in order to achieve the desired properties both in the focal path and in the carrier body. The duration of a heat treatment carried out after the forging process is in particular a few hours, for example in the range of 1-5 hours.

According to a development, the forged body after completion of the forging a degree of deformation of at least 20%, in particular in the range of 20% to 60%. However, it is also possible to achieve degrees of deformation of up to 80%. Forcing is particularly parallel to the rotational axis of symmetry of the X-ray rotary anode, which is aligned exactly or essentially perpendicular to the focal plane (s). In this case, the ratio of the change in height of the respective body, which is achieved parallel to the direction of the force of action, relative to its starting height (along the direction of the force of action) is referred to as degree of deformation.

Fig. 1A-1C:

schematische Darstellungen zur Veranschaulichung unterschiedlicher Rekristallisationsgrade;

Fig. 2:

ein schematisches Diagramm zur Veranschaulichung des Härteverlaufs in Abhängigkeit von der Temperatur einer Wärmebehandlung;

Fig. 3:

eine schematische Querschnittansicht einer Röntgendrehanode;

Fig. 4A-4D:

eine schematische Darstellung zur Veranschaulichung einer EBSD-Analyse;

Fig. 5A-5C:

inverse Polfiguren der Brennbahn einer erfindungsgemäßen Röntgendrehanode entlang unterschiedlicher Richtungen;

Fig. 6:

inverse Polfigur einer Brennbahn, die mittels CVD aufgebracht wurde; und

Fig. 7:

inverse Polfigur einer, durch Vakuum-Plasmaspritzen aufgebrachten Brennbahn.

Further advantages and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures. From the figures show:

Fig. 1A-1C:

schematic representations to illustrate different degrees of recrystallization;

Fig. 2:

a schematic diagram illustrating the hardness profile as a function of the temperature of a heat treatment;

3:

a schematic cross-sectional view of an X-ray rotary anode;

4A-4D:

a schematic representation illustrating an EBSD analysis;

FIGS. 5A-5C:

inverse pole pieces of the focal path of an inventive X-ray rotary anode along different directions;

Fig. 6:

inverse pole figure of a focal path, which was applied by CVD; and

Fig. 7:

Inverse pole figure of a deposited by vacuum plasma spraying focal path.

The following explanation of the FIGS. 1A-1C and 2 identifies criteria by which a non-recrystallized structure, a partially recrystallized structure, and a (complete) recrystallized structure can be distinguished from each other. Furthermore, with reference to these figures, parameters are explained by means of which the degree of recrystallization can be stated. These explanations apply both in relation to the focal track and in relation to the carrier body. In the Figures 1A-1C In this case, schematically (greatly enlarged) structures are shown, as can be represented for example in an electron micrograph of a suitably prepared ground surface, in particular in the context of an EBSD analysis (EBSD: Electron Backscatter Diffraction). A suitable method for sample preparation, a suitable measuring arrangement and a suitable measuring method are described with reference to FIGS FIGS. 4A to 4D explained. As is known in the art, the grain boundaries (and optionally also the small angle grain boundaries) and the dislocations in such an electron micrograph can be visualized. For this purpose, a minimum rotation angle is specified, from which point a grain boundary is drawn. Both FIGS. 1A to 1C is (apart from that, in Fig. 1B section shown separately) assumed that a minimum rotation angle of 15 ° was specified, so that the course of the large-angle grain boundaries (or grain boundary sections) can be seen. In Fig. 2 is, starting from an initial hardness -AH-, which is obtained in the context of powder metallurgy production after the forging process (initial hardness -AH- the forming structure), schematically the dependence of the hardness of the temperature -T- a subsequent heat treatment (stress relief annealing), which is performed over a predetermined period of time -t-, such as over a period of one hour. If the heat treatment is carried out over a longer, predetermined period of time, the shifts in Fig. 2 1 to the left (ie, toward lower temperatures), while it shifts to the right (ie, toward higher temperatures) for a shorter period of time.

In Fig. 1A is a pure forming structure, as obtained for example after a forging process (which is carried out in the context of powder metallurgical production) is shown. As is known in the art, such a reforming structure does not have clear grain boundaries around corresponding crystal grains. Rather, only grain boundary sections -2- can be seen, each having an open beginning and / or an open end. In some cases (depending on the degree of deformation during the forging process), sections of the grain boundaries of the original grains of the sintered product can also be identified. Furthermore, form by the forming (forging) Transfers -4-, which in the Fig. 1A and 1B represented by the symbol "⊥" and new grain boundary sections -2-. The original grains of the seedling, if still recognizable, are severely squeezed and distorted due to reshaping. Furthermore, the forming structure has a substructure that can be made visible in the context of an EBSD analysis of the respective ground surface when setting a smaller minimum rotation angle. This substructure of the forming structure will be explained below with reference to FIG Fig. 1B explained. With increasing degree of deformation, the original grain boundaries (the grains of the sintered product) disappear in sections or even completely. The intensity and frequency of these typical features of the forming structure depends, inter alia, on the (material) composition and the degree of deformation. In particular, it should be noted that with increasing degree of deformation small angle grain boundary sections increasingly occur and also the frequency of large angle grain boundary sections increases. A determination of the average grain size, which regularly takes place in the case of uniform structures according to the standard ASTM E 112-96, is not possible because (at least at a minimum angle of rotation of 15 °) only grain boundary sections are recognizable.

Recovery processes usually take place in the forming structure, which increase with increasing temperature. For such recovery processes, which can be seen, for example, in the disappearance and / or ordering of dislocations, no activation energy is required. These recovery processes lead to a decrease in hardness. In this area -EH- the recovery operations (range up to T ₁ in Fig. 2 ) the hardness decreases continuously with increasing temperature, the slope in this range -EH- being relatively flat (cf. Fig. 2 ). Above a certain temperature -T ₁ - the activation energy required for grain regeneration during the recrystallization can be applied. This temperature -T ₁ - depends inter alia on the composition and the degree of deformation of the forming structure and on the duration of the heat treatment carried out in each case. If a recrystallization occurs, then there is (initially) a partially recrystallized structure. In Fig. 1B a partially recrystallized structure is shown having some grain grains formed by grain remodeling. The crystal grains (or crystallites) -6- each have circumferential grain boundaries -8-, which can be represented for example in an electron micrograph of a suitably prepared ground surface, in particular in the context of an EBSD analysis (EBSD: Electron Backscatter Diffraction) are. The remaining (or the crystal grains -6-surrounding) Proportion of partially recrystallized structure still exists in the forming structure. Due to the grain regeneration as well as partly due to recovery processes, the dislocations occurring in the forming structure increasingly disappear.

As already mentioned, another feature of the forming structure is that it has a substructure. Such a substructure can be visualized in an EBSD analysis by specifying a smaller minimum rotation angle, such as by a minimum rotation angle of 5 ° (or possibly even an even smaller angle). In this way, in addition to the large-angle grain boundaries (grain boundary sections -2- and circumferential grain boundaries -8-) also the small-angle grain boundaries -9-, which form the substructure, recognizable. This is in Fig. 1B in the lower box, in which a section of the structure shown in the box above is shown enlarged. The small-angle grain boundaries -9- of the substructure are shown in thinner lines in this illustration. As can be seen from this illustration, the large-angle grain boundaries of the grain boundary sections -2- are still partly continued by small-angle grain boundaries -9-. The crystal grains -6- produced by grain regeneration are free of the structure. In the case of the inventive X-ray rotary anode, the substructure -9- of the forming structure is, in particular, of fine-grained design.

With increasing recrystallization, which increases with the temperature (and also the time) of the heat treatment, the hardness decreases sharply (cf. Fig. 2 ). In Fig. 2 goes from the temperature -T ₁ - the previously gently sloping graph in a region with steeply sloping slope over. The transition region between the gently sloping section and the steeply sloping section of the graph, in particular the point with the highest curvature, is called the recrystallization threshold -RKS- (cf. Fig. 2 ). As the degree of recrystallization increases, the crystal grains that have already formed as a result of new grain formation increase, as a result of the formation of grain new crystal grains are formed and the forming structure disappears increasingly. In particular, the forming structure is increasingly being "consumed" by the crystal grains produced by grain remodeling. With a further increase in the degree of recrystallization, the grain boundaries of the crystal grains formed by grain formation collide and eventually (at least to a large extent) also fill in the remaining interstices. At this stage, crystal growth slows down again and again Fig. 2 flatten the slope of the graph from. A state is achieved in which the recrystallization is completed by 99 °, in particular in which the crystal grains formed by grain formation have a surface area of 99% with respect to a cross-sectional area through the structure. The recrystallization temperature, which in Fig. 2 -T ₂ - corresponds to (in Fig. 2 If the duration of the heat treatment is one hour), it is defined such that after a heat treatment of one hour at this recrystallization temperature, the recrystallization is 99% complete. The region -RK- extending from the temperature -T ₁ - beginning at the recrystallization temperature -T ₂ - is referred to as the recrystallization region because recrystallization processes occur to a considerable extent within it. Finally, the graph goes into an area -EB-, in which it no longer or only very flat drops. Grain growth still occurs in this region, but there is no recrystallization or only a very small amount of recrystallization (in particular of the remaining one percent of the structure).

In Fig. 1C is an idealized, fully recrystallized structure shown. The grain boundaries of the crystal grains formed by grain remodeling directly adjoin one another. The original forming structure has completely disappeared. It is in Fig. 1C the "ideal case" of a fully recrystallized structure shown, since the grain boundaries each adjacent to each other along their entire extension direction.

In Fig. 3 is schematically shown the structure of a Röntgendrehanode -10-, which is rotationally symmetrical to a rotational axis of symmetry -12- is formed. The X-ray rotary anode -10- has a plate-shaped carrier body -14- which can be mounted on a corresponding shaft. On the cover side, on the support body -14- an annular focal path -16- applied, which has a truncated cone shape (of a flat cone) in the illustrated embodiment. The focal track 16 covers at least one region of the carrier body 14 which, in use, is traversed by an electron beam. As a rule, the focal track covers a larger area of the carrier body than that of the path of the electron beam. The outer shape and the structure of the X-ray rotary anode -10- can, as is known in the art, deviate from the illustrated X-ray rotary anode. As based on the Fig. 3 can be seen, the (macroscopic) portion of the non-recrystallized and / or partially-recrystallized structure (both in the focal path and in the carrier body) can be generally determined by a radial (ie through the axis of rotation symmetry -12- extending ) and is examined perpendicular to the focal plane plane cross-sectional area then, which areas are present in a non-recrystallized and / or in a partially-recrystallized structure.

The following is with reference to the FIGS. 4A to 4D a, with a scanning electron microscope feasible EBSD analysis (EBSD: Electron Backscatter Diffraction; German: electron diffraction) explained. Within the framework of such an EBSD analysis, a characterization of the respective structure can be carried out on a microscopic level. In particular, within such an EBSD analysis, the fine granularity of the respective structure can be determined, the appearance and extent of substructures can be determined, the proportion of grain grains formed by grain remodeling in a partially recrystallized structure, and preferred texture textures occurring in the structure. For this purpose, as part of the sample preparation, a cross-sectional area which extends radially and perpendicular to the focal plane (corresponds to, in FIG Fig. 3 Cross-sectional area shown) produced by the X-ray rotary anode. The preparation of a corresponding ground surface is effected in particular by embedding, grinding, polishing and etching at least a portion of the obtained cross-sectional area of the X-ray rotary anode, the surface subsequently being further ion-polished (for removal of the deformation structure on the surface resulting from the grinding process). In this case, the ground surface to be examined can in particular be chosen such that it has a section of the focal path and a section of the carrier body of the X-ray rotary anode, so that both sections can be examined. The measuring arrangement is such that the electron beam impinges on the prepared ground surface at an angle of 20 °. In the scanning electron microscope (in the present case: Carl Zeiss "Ultra 55 plus"), the distance between the electron source (here: field emission cathode) and the sample 16, 2 mm and the distance between the sample and the EBSD camera (in this case: "DigiView IV" ) is 16 mm. The details given in parentheses relate to the types of equipment used by the applicant, and in principle also other types of equipment, which allow the described functions, are used in a corresponding manner. The acceleration voltage is 20 kV, a 50-fold magnification is set, and the pitch of the individual pixels on the sample, which are scanned in succession, is 4 μm.

The individual pixels 17 are arranged in equilateral triangles with each other, the side length of a triangle in each case corresponding to the grid spacing -18- of 4 μm (cf. Fig. 4A ). The information for a single pixel -17- come from a volume of the respective sample, which has a surface with a diameter of 50 nm (nanometers) and a depth of 50 nm. The representation of the information of a pixel is then in the form of a hexagon -19- (in Fig. 4A dashed lines) whose sides each form the mid-perpendicular between the respective pixel -17- and the respective nearest (six) pixels -17-. The examined sample area -21- is in particular 1,700 μm by 1,700 μm. As in Fig. 4B In the present case, in an upper half it comprises a focal section -22- (in cross-section) of approximately 850 by 1,700 μm ² and in the lower half a support body section -24- (in cross section) of approximately 850 by 1,700 μm ² . The interface -26- (between the focal track and the carrier body) runs parallel to the focal plane and centrally through the examined sample surface -21- (in each case parallel to their sides). Furthermore, it runs parallel to the radial direction -RD- (cf., for example, direction -RD- in FIG Fig. 3, 4B ). As above with reference to Fig. 4A is explained, the examined sample surface -21- is scanned with a grid of 4 microns.

For the determination of the mean grain boundary distance (or small-angle grain boundary distance) grain boundaries and grain boundary sections with a grain boundary angle greater than or equal to a minimum rotation angle are visualized within the examined sample surface -21- within the scope of the EBSD analysis. In the present case, a minimum angle of rotation of 15 ° in the scanning electron microscope is set to determine the mean grain boundary distance. The investigated section of the X-ray rotary anode has a (total) degree of deformation of 60%. It should be noted that due to the high hardness of the focal point of the (local) degree of deformation of the focal path is lower per se, while the (local) degree of deformation of the carrier body is at least partially higher. In particular, the degree of deformation of the carrier body away from the focal path increases in a direction perpendicular to the focal plane in the downward direction. Accordingly, the result of the investigation depends on the (total) degree of deformation of the examined section as well as on the position of the investigated sample surface -21-. Because of the explained position of the examined sample surface -21- in the region of the interface -26-, both the investigated focal-web section -22- and the investigated carrier body section -24- are less than 1-mm from the interface -26- (this is particularly relevant with respect to the carrier body in which, depending on the height, ie in a direction parallel to the rotational axis of symmetry, different degrees of deformation occur). Within the examined sample surface -21-grain boundaries or grain boundary sections are always determined and displayed between two grid points -17 by the scanning electron microscope if an orientation difference of the respective grid of ≥ 15 ° is determined between the two grid points -17- (becomes another Minimum rotation angle set, the latter is decisive). The orientation difference used is in each case the smallest angle which is required in order to convert the respective crystal lattices which are present at the respective grid points 17 to be compared into one another. This process is performed at each grid point -17- with respect to all grid points surrounding it (ie, each with respect to six surrounding grid points). In Fig. 4A For example, a grain boundary portion -20 is shown. In this way, within the investigated sample surface -21-, a grain boundary pattern -32- formed in the case of a partially recrystallized structure (at a minimum rotation angle of 15 °) through grain boundary portions and circumferential grain boundaries is obtained. This is in the Figs. 4C and 4D shown schematically for a section -28- of the focal path. If a minimum rotation angle of 5 ° is set, then additionally the small-angle grain boundaries of the substructure can be made visible (these are in the Figs. 4C and 4D not shown).

In the following, the determination of the average grain boundary distance of the focal-web material parallel to the focal plane is explained. In order to determine the grain boundary distance of the material of the track material, only the focal point segment-22- of approximately 850 by 1,700 μm ^{2 of} the examined sample surface -21- is evaluated. In this case, in the presently explained method, the mean grain boundary distance along the direction -RD-, ie along a plane parallel to the focal plane (or to the interface -26- in Fig. 4B ) and substantially radially extending direction. For this purpose, within the investigated sample surface -21- (which has an area of 1,700 × 1,700 μm ² ) in the grain boundary pattern -32- a family of -34- of 98 lines each with a length of 1,700 μm and a relative distance of 17.2 μm (1,700 μm / 99). In Fig. 4C this is shown schematically for a section of the focal track situated within the examined focal point section -22-. The Linienschar -34- runs parallel to the examined surface (resp. Cross-sectional area) and the individual lines each extend parallel to the direction -RD-. The distances between in each case two, mutually adjacent points of intersection of the respective line with lines of the crown boundary pattern -32-are determined on the individual lines. In the areas where the end of a line does not intersect with a line of the grain boundary pattern -32- (ie, forms an open end because it reaches the boundary of the examined focal-course section -22-), the length of the section becomes Line end evaluated to the first intersection with a line of the grain boundary pattern -32-as a half crystal grain. The frequency of the different distances determined within the focal section -22- (approximately 850 x 1.700 μm ² ) is evaluated and then an average of the distances is formed (corresponds to the sum of the detected distances divided by the number of measured distances) , The method described for determining the mean grain boundary distance is also referred to as "intercept length". The determination of the mean grain boundary distance perpendicular to the focal plane, ie along the direction -ND-, takes place within the focal section -22- accordingly. Again, a family of -36- (again 98) lines are placed in the grain boundary pattern -32-. The Linienschar -36- runs parallel to the surface being examined (or cross-sectional area) and the individual lines are each parallel to the direction -ND-. In Fig. 4D this is again shown schematically for the section -28-. The evaluation of the distances is carried out accordingly, as explained above. In this way, a measure of the fine grain of the structure formed of (large-angle) grain boundaries and (large-angle) grain boundary portions can be given. The mean grain boundary distance parallel to the focal plane is generally greater than the mean grain boundary distance perpendicular to the focal plane. This effect is due to the force applied perpendicular to the focal plane during the forging process. The average grain boundary distance d can then be determined from the mean grain boundary distance parallel to the focal plane plane d _p and the average grain boundary distance perpendicular to the focal plane d _s , as can be seen from the following equation: $$d=\sqrt{d_p\times d_s}$$

In a corresponding manner, the determination of the mean (small angle) grain boundary distance of the section of the focal track can be performed in parallel as well as perpendicular to the focal plane by specifying a minimum rotation angle of 5 ° become. From this, in turn, the average small-angle grain boundary distance can be determined according to the formula given above. By specifying a minimum rotation angle of 5 °, the small angle grain boundaries of the substructure (which is present in the deformation structure) are additionally taken into account. In this way, a measure of the fine graininess of the structure formed of (large angle) grain boundaries, (large angle) grain boundary portions and small angle grain boundaries can be given.

The degree of recrystallization can be determined on the microscopic level by specifying in a micrograph such as, for example, US Pat Fig. 1A-1C is shown schematically, the area ratio of the, formed by Kornneubildung crystal grains (relative to the total area of the examined section) is determined. This determination can in turn be made with a scanning electron microscope in the context of an EBSD analysis. In this regard, the above with reference to the FIGS. 4A to 4D explained measuring arrangement and sample preparation and the illustrated measuring method reference. In particular, an angle of ≥ 15 ° is specified as the minimum rotation angle, so that the course of the large-angle grain boundaries can be seen. In this way, it is possible in particular to determine the circumferential grain boundaries of the crystal grains produced by grain regeneration as well as the (large-angle) grain boundary sections. In addition, the same range can also be examined by specifying a minimum rotation angle of ≥ 5 ° (or another small value for the minimum rotation angle) to check whether the individual crystal grains are crystal grains formed by grain remodeling act (they have no substructure). Subsequently, the ratio of the area of the crystal grains formed by grain remodeling relative to the entire area under investigation is determined.

Furthermore, the degree of recrystallization can also be estimated from the hardness. This can be done, for example, by subjecting a plurality of identically produced samples each time after the forging process to heat treatments at a different time for a predetermined period of time (if appropriate, the duration of the heat treatment may additionally or alternatively be varied). A hardness measurement is then carried out on the samples at the same position (within the sample). Thus, in essence, the course of, in Fig. 2 Traced curve shown and it can be determined in which area of the curve the respective sample is located. As explained above, the recrystallization threshold -RKS- is preferably used within the range-TB- (the range -TB-in Fig. 2 schematically represented by the dashed circle around the recrystallization threshold -RKS-).

As part of the determination of the degree of recrystallization is generally considered that occur in certain materials (eg molybdenum and molybdenum alloys) pronounced recovery operations (English term: extended recovery). These recovery processes can also lead to germs for a new grain formation, according to some views. If grain nucleation takes place from these germs, this type of grain regeneration is also included within the scope of this description with the term recrystallization. If pronounced recovery processes occur, then the graph falls into Fig. 2 in the recovery process -EH- already stronger and the recrystallization threshold can shift to higher temperatures. The graph then proceeds at least in the region -EB-, in which the structure is recrystallized, again corresponding to a material without pronounced recovery processes. In particular, there is a qualitative difference as shown in Fig. 2 is shown schematically by the dashed line. In the case of molybdenum-based alloys, this effect is additionally superimposed by the formation of particles, which can also have an effect on the concrete curve course. Qualitatively, however, the curve is always essentially as it is in Fig. 2 is shown.

Hereinafter, the production of an X-ray rotary anode according to an embodiment of the present invention will be explained. First, the starting powders for the carrier body are mixed and the starting powders for the focal path are mixed. The starting powders for the carrier body are chosen such that for the carrier body (apart from impurities) a composition of 0.5 wt.% Ti, 0.08 wt.% Zirconium, 0.01-0.04 wt.% Carbon, less is obtained as 0.03% by weight of oxygen and the remaining portion of molybdenum (after completion of all the heat treatments carried out in the powder metallurgical production) (ie TZM). Furthermore, the starting powders are chosen such that a composition of 10% by weight of rhenium and 90% by weight of tungsten is obtained for the fuel track (apart from impurities). The starting powders are pressed together with 400 tons (equivalent to 4 * 10 ⁵ kg) per X-ray rotary anode. Then the obtained body is added Temperatures in the range of 2,000 ° C - 2,300 ° C sintered for 2 to 24 hours. In particular, the starting body (sintering) obtained after sintering has a relative density of 94%. The starting body obtained after sintering is forged at temperatures in the range of 1300 ° C to 1500 ° C (preferably 1300 ° C), the body after the forging step having a degree of deformation in the range of 20-60% (preferably of 60%). After the forging step, a heat treatment of the body is carried out at temperatures in the range of 1300 ° C to 1500 ° C (preferably 1400 ° C) for 2 to 10 hours. Insofar as area indications are made in the context of this exemplary embodiment, good results can be achieved in each case for different combinations within the respective area. While the specified parameters in the pressing step and in the sintering step are less critical for the inventive properties of the focal track (and essentially also for the described advantageous properties of the carrier body), the temperatures in particular during the forging step and in the subsequent heat treatment on the properties of the focal track (in particular on their degree of recrystallization). In particular, particularly good results are obtained at the preferred temperature values at the forging step and at the subsequent heat treatment step (at the 60% preferred degree of deformation).

In the case of X-ray rotary anodes which were produced according to the exemplary embodiment explained above, a hardness of 450 HV 30 and, in the case of the carrier body, a hardness of 315 HV 10 could be achieved in the case of the focal track. The hardness measurements are to be carried out at one, extending through the axis of rotation symmetry cross-sectional area. In the case of the support body, a 0.2% proof stress R _p 0.2 of 650 MPa (Mega Pascal) and an elongation at break A of 5% could be obtained at room temperature. In this case, a sample extending radially in the carrier body is to be used as a measurement sample. The measuring method to be used is method B, which is based on the voltage velocity and described in DIN EN ISO 6892-1. By comparison, conventional powders produced by powder metallurgy (with the exception of special alloys and materials reinforced with additional particles) typically achieve hardnesses of at most 220 HV 10 and also lower yield strengths.

Accordingly, these results show that in the X-ray rotary anodes according to the invention significantly higher hardnesses (of the focal path and also of the carrier body) and higher yield strengths (at least in the case of the carrier body) are achieved than with conventional powder metallurgically produced X-ray rotary anodes. Furthermore, these investigations show that a sufficient ductilization of the carrier body material can be achieved by a heat treatment following the forging process at temperatures in the region of the recrystallization threshold (of the carrier body material). At such a "gentle" ductilization (i.e., heat treatment at comparatively low temperatures) it is at the same time achieved that the structure of the kerf remains very fine-grained. The achieved ductilization can be recognized in particular on the basis of the values obtained for the elongation at break A at room temperature. For a non-heat treated sample, the elongation at break of the (pressed, sintered and forged) carrier body material is typically ≤ 1%. By ductilization can be avoided that the X-ray rotary anodes are brittle and fragile.

At inventively designed X-ray rotating anodes, the focal point was examined at the end of its service life. It was found that cracks are deflected along the grain boundaries of the fine-grained structure and thus change the direction of propagation several times. Due to this crack deflection along the fine-grained structure, crack propagation deep into the focal track is avoided. It was also possible to observe a uniformly distributed crack pattern with uniformly formed cracks on the surface of the focal point at the end of its service life. In contrast, at comparative X-ray rotary anodes, in which the focal track was produced by vacuum plasma spraying, the crystals of the track are stalk-shaped and aligned perpendicular to the focal plane. As a result, a crack spreads along the grain boundaries deep into the focal path (and eventually down to the support body).

For examining the texture of the focal track and the carrier body, an X-ray rotary anode was used, as described above with reference to FIGS FIGS. 4A to 4D is prepared as prepared sample to be examined. The X-ray rotary anode was designed according to the invention. The hearth had (apart from impurities) a composition of 90 wt% tungsten and 10 wt% rhenium, while the support body (apart from impurities) had a composition of 0.5 wt% Ti, 0.08 wt% zirconium , 0.01-0.04 wt% carbon, less than 0.03 wt% oxygen and the remaining portion of molybdenum. The measuring arrangement corresponds to the arrangement explained above. In the measuring method, the above, with reference to the FIGS. 4A to 4D used settings, provided that they are applicable or to determine the texture. The inverse pole figures obtained as part of the EBSD analysis of the focal track are in the Figs. 5A-5C shown. In this case, with respect to the focal track, the macroscopic, mutually perpendicular directions -ND-, which is perpendicular to the focal plane in the respective investigated area, -RD-, which runs substantially radially and parallel to the focal plane and TD-, which is tangent and parallel to the focal plane, defined (these directions are for illustration in FIG Fig. 3 shown). The force in the forging process during the manufacturing process of the associated X-ray rotary anode was perpendicular to the focal plane (ie along the direction -ND-). In Fig. 5A is the inverse pole figure of the focal path in the direction -ND-, in Fig. 5B is the inverse pole figure towards -RD- and in Fig. 5C the inverse pole figure is shown in the direction -TD-. Based on Fig. 5A the pronounced preferential texturing of the <111> direction and the <001> direction along the direction -ND- can be recognized. Furthermore, based on the Figures 5B and 5C to recognize the (less strong) pronounced preferential texturing of the <101> direction along the directions -RD and -TD-. For the texture of the carrier body, which was determined in the outer region of the X-ray rotary anode, corresponding results were achieved. In particular, a pronounced preferential texturing of the <111> direction and the <001> direction along the direction -ND- and a (slightly less pronounced) preferential texturing of the <101> direction along the directions -RD- and -TD- measured.

For comparison, correspondingly prepared samples of a, by CVD method applied focal path of pure tungsten (see. Fig. 6 ) and a focal line produced by vacuum plasma spraying (cf. Fig. 7 ) of a tungsten-rhenium alloy (tungsten content: 90% by weight, rhenium content: 10% by weight) in view of the texture thereof. In Fig. 6 the inverse pole figure is shown in the direction -TD-. As based on the Fig. 6 As can be seen, the deposited by CVD coating focal line on a preferred texturing of the <111> direction along the direction -TD-. In Fig. 7 the inverse pole figure is shown in the direction of -ND-. As based on the Fig. 7 As can be seen, the focal web produced by vacuum plasma spraying has pronounced preferential texturing of the <001> direction along the direction ND-.

Claims (17)

X-ray rotary anode, which has a carrier body (14) and a focal path (16) formed on the carrier body (14),
wherein the carrier body (14) and the focal track (16) are produced by powder metallurgy in a composite, the carrier body (14) is formed from molybdenum or a molybdenum-based alloy, and the focal path (16) is made from a tungsten-rhenium alloy with a rhenium alloy. Proportion is formed in a range of 5-10 wt.%,
characterized,
that at least a portion of the internal web (16) is not recrystallized in the finally heat-treated X-ray rotary anode (10) in one and / or is present in a partially-recrystallized structure, and has a hardness of ≥ 350 HV 30th X-ray rotary anode according to claim 1, characterized in that the portion of the focal track perpendicular (ND) to a focal plane a preferential texturing of the <111> direction with an X-ray diffraction determinable texture coefficient TC ₍₂₂₂₎ of ≥ 4 and a preferred texturing the <001> direction has an X-ray diffraction-determinable texture coefficient TC ₍₂₀₀₎ of ≥ 5. X-ray rotary anode according to claim 1 or 2, characterized in that at the section of the focal track (16) perpendicular (ND) to the focal plane, the following relationship of the X-ray diffraction determinable texture coefficients TC ₍₂₂₂₎ and TC _{(310) is} fulfilled: $$\frac{{\mathit{TC}}_{\left(222\right)}}{{\mathit{TC}}_{\left(310\right)}}\ge \mathrm{5th}$$

X-ray rotary anode according to one of the preceding claims, characterized in that the section of the focal track (16) is present in a partially recrystallized structure. X-ray rotary anode according to claim 4, characterized in that in the partially-recrystallized structure by grain formation resulting crystal grains (6) are surrounded by a forming structure and that with respect to a cross-sectional area through the partially recrystallized structure these crystal grains (6) have an area ratio in the range of 10% to 80%. X-ray rotary anode according to one of the preceding claims, characterized in that the section of the focal track (16) has an average small-angle grain boundary distance of ≤ 10 μm, - wherein the average small-angle grain boundary distance can be determined by a measuring method in which at a radial, perpendicular to the focal plane extending cross-sectional area in a region of the portion of the focal path (16) grain boundaries (8), grain boundary sections (2) and small-angle grain boundaries (9) are determined with a grain boundary angle of ≥ 5 °, - For determining the average small-angle grain boundary distance parallel to the focal plane in the resulting grain boundary pattern (32), a parallel to the cross-sectional area extending line (34) from each parallel to the focal plane extending lines, each with a distance of each have 17.2 microns is placed on each line, the distances between each two adjacent intersections of the respective line with lines of the grain boundary pattern (32) are determined and the average of these distances as a mean small-angle grain boundary distance parallel to the focal point Level is determined - For determining the average small-angle grain boundary distance perpendicular to the focal plane in the resulting grain boundary pattern (32) extending parallel to the cross-sectional area line (36) from each perpendicular to the focal plane extending lines, each with a distance of 17 each , 2 microns is placed on each line, the distances between each two adjacent intersection points of the respective line with lines of the grain boundary pattern (32) are determined and determines the average of these distances as a mean small-angle grain boundary perpendicular to the focal plane will, and the mean small angle grain boundary distance is determined as the geometric mean of the mean small angle grain boundary distance parallel to the focal plane and the mean small angle grain boundary distance perpendicular to the focal plane. X-ray rotary anode according to one of the preceding claims, characterized in that the section of the focal track (16) in directions parallel to the focal plane (RD, TD) has a preferred texturing of the <101> direction. X-ray rotary anode according to one of the preceding claims, characterized in that at least a portion of the carrier body (14) is present in a non-recrystallized and / or in a partially recrystallized structure. X-ray rotary anode according to claim 8, characterized in that the portion of the carrier body (14) has a hardness of ≥ 230 HV 10. X-ray rotary anode according to claim 8 or 9, characterized - That the portion of the support body (14) perpendicular (ND) to the focal plane has a preferential texturing of the <111> direction and the <001>direction; and or - That the portion of the carrier body (14) in directions (RD, TD) parallel to the focal plane has a preferred texturing of the <101> direction. X-ray rotary anode according to one of claims 8 to 10, characterized in that the portion of the carrier body (14) at room temperature has an elongation at break of ≥ 2.5%. X-ray rotary anode according to one of the preceding claims, characterized in that the carrier body (14) is formed from a molybdenum-based alloy whose further alloying constituents are formed by at least one element of the group Ti, Zr, Hf and by at least one element of the group C, N. become. A method of manufacturing an X-ray rotary anode (10) according to any one of claims 1 to 12, comprising the following steps: A) providing an output body made by pressing and sintering respective starting powders in combination with a carrier body portion of molybdenum or a molybdenum-based mixture and a focal length section formed of a tungsten-based mixture formed on the carrier body portion; B) forging the body; and C) performing a heat treatment of the body at and / or after the forging step; wherein the heat treatment is performed at such low temperatures and for such a period of time that, in the finally heat treated X-ray rotary anode (10), at least a portion of the focal path (16) obtained from the focal section comprises a tungsten-rhenium alloy having a rhenium Portion is in a range of 5-10 wt.%, Is present in a non-recrystallized and / or partially recrystallized structure and has a hardness of ≥350 HV30. A method according to claim 13, characterized in that the heat treatment at temperatures in a range of 1,300 - 1,500 ° C is performed. A method according to claim 13 or 14, characterized in that the forged body after completion of the forging has a degree of deformation in the range of 20% to 60%. X-ray rotary anode, which has a carrier body (14) and a focal path (16) formed on the carrier body (14),
wherein the carrier body (14) and the focal track (16) are produced by powder metallurgy in a composite, the carrier body (14) is formed from molybdenum or a molybdenum-based alloy, and the focal path (16) is formed from tungsten or a tungsten-based alloy .
characterized,
that at least a portion of the internal web (16) is not recrystallized in the finally heat-treated X-ray rotary anode (10) in one and / or is present in a partially-recrystallized structure. A method of manufacturing an x-ray rotary anode (10) according to claim 16, comprising the following steps: A) providing an output body made by pressing and sintering corresponding starting powders in composite with a carrier body portion of molybdenum or a molybdenum-based mixture and a tungsten or tungsten based compound focal path portion formed on the carrier body portion; B) forging the body; and C) performing a heat treatment of the body at and / or after the forging step; wherein the heat treatment is carried out at such low temperatures and for such a period of time that in the finally heat-treated X-ray rotary anode (10) at least a portion of the focal path (16) obtained from the focal section is in a non-recrystallized and / or partially recrystallized Structure exists.

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