EP2666180A1 - Rotary x-ray anode - Google Patents

Abstract

The invention relates to a rotary X-ray anode (10), which comprises a support body (14) and a focal track (16) formed on the support body (14). The support body (14) and the focal track (16) are produced as a composite by powder metallurgy; the support body (14) is made of molybdenum or a molybdenum-based alloy and the focal track (16) is made of tungsten or a tungsten-based alloy. In the subsequently heat-treated rotary X-ray anode (10) at least a portion of the focal track (16) is present in a non-recrystallised and/or partially re-crystallised structure.

Description

 X ROTARY ANODE

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 of

 X-ray rotating 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 one on which

Carrier body formed coating, which is designed specifically for the generation of X-rays and is referred to in the art as Brermbahn, on. The carrier body and the focal track are formed of refractory materials. The focal track usually covers at least the area of the carrier body, which in use the

Electron beam is exposed. 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 the powder metallurgical

 Production in which the carrier body and the Brerm web 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. On the carrier body occur due to the high temperatures and temperature gradients and due to the high

Rotation speeds relatively high thermal and mechanical stresses. 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 carrier body are largely stable to subsequent microstructural changes (for example to recrystallization, etc.) even at the high temperatures used. The taking place within the scope of the previous powder metallurgical production

 However, recrystallization in the focal lane leads to relatively large grain sizes. Such

Structures involve the risk of forming relatively deep and wide cracks that 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. Especially at high

Temperatures and high mechanical loads can then be a plastic

Deformation of the carrier body (especially when exceeding the yield stress) occur. Especially in the high power range, where a high dose rate (resp.

Radiation power) available and the rotational speed of the X-ray rotary anode is comparatively high, these critical values are exceeded in part. 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

(cf., for example, US 2005/0135959 AI). US Pat. No. 6,487,275 B1 describes an X-ray rotary anode with a Wofram-Rhenium alloy focal track which has a grain size of 0.9 μm to 10 μm and which, within the scope of a CVD coating method (CVD: chemical vapor deposition; Chemical vapor deposition) can be produced.

Accordingly, the object of the present invention is to provide a

To provide powder metallurgically produced in the composite X-ray rotary anode, which allows a high dose yield over long periods of use and a high

Life has.

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 track are made by powder metallurgy in the composite, the

Carrier body is formed of molybdenum or a molybdenum-based alloy, and the focal lane is formed of 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 has none

Grain formation (in the case of a non-recrystallized structure) or only to a proportion of significantly less than 100% by Kornneubildung 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 when using). 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 in use) locally recrystallized structure of the slurry web remains considerably finer-grained than in the recrystallization processes within the scope of the conventional one

Manufacturing process, in particular the conventional, powder metallurgical

 Manufacturing process, the case is. 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 inventive

X-ray anode 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 track under the influence of

Electron beam is that takes place by the action of the electron beam a shock-like transformation. 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.

At a certain composition of the focal length can with increasing

Forming degree (which is set in the step of forming, especially forging), a higher starting hardness (and a higher starting strength) can be obtained. 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 crystal 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%. Is that

Area fraction of the crystal grains formed by grain regeneration in the range below 5% or are not present at all, formed by grain nucleation crystal grains in the structure, it is assumed in the present context of a non-recrystallized structure. 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 below

Related to the description of Fig. 4A-4D indicated.

The X-ray rotary anode according to the invention is in particular a

High-performance X-ray rotary anode, which is designed for a high radiation power (or dose rate) and a high rotational speed. Such

 High-performance x-ray rotary anodes are used in particular in the medical field, such as in computed tomography (CT) and cardiovascular applications (CV). In general, on the carrier body, in particular on the side facing away from the focal point side, also other layers, attachments, etc., such as

For example, a graphite block, etc. may be provided. 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 back of the support body, a graphite body (for example, by soldering, diffusion bonding, etc.) may be appropriate. Alternatively, the X-ray rotary anode but also for lower

 Radiation services to be designed. 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. When

Carrier body material may also be used in particular special alloys with high strength and hardness and / or atomic impurities or particles may be added to the respective carrier body material to increase the strength. According to a development, the molybdenum-based alloy has a share of at least

 80 (wt.%: Weight percent) molybdenum, in particular of at least 98 wt.% Molybdenum on. With a tungsten-based alloy is particularly referred to an alloy having tungsten as the main component. In particular, the focal lane is formed from a tungsten-rhenium alloy having a rhenium content of up to 26% by weight. 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 "final heat-treated x-ray rotary anode" is understood to mean that all of these are carried out in the context of powder metallurgical production

Has undergone heat treatment (s). 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 in use), as was the case after completion of the powder metallurgical production

Heat treatment (s) is present. 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. The "section" of the focal track refers in particular to a macroscopic contiguous section (ie comprising a multiplicity of grain boundaries and / or grain boundary sections) of the focal track, whereby several sections of the claimed characteristics may also be present , over which (in use) the path of the electron beam passes, the claimed properties, in particular the focal track has the claimed properties over its entire range, with a "non-recrystallized and / or partially recrystallized structure" reference is made to a structure which can not be exclusively recrystallized exclusively

may be partially recrystallized or partially unrecrystallized and partially

partially recrystallized in sections.

According to a development, the section of the focal track perpendicular to a

Focal plane a preferred texturing of the <111> direction with a, about

X-ray diffraction (XRD: X-ray diffraction) determinable texture coefficient TC ₍₂₂₂₎ of> 4 and a preferred texturing of the <001> direction with a, about

X-ray diffraction determinable texture coefficient TC ( ₂₀ o ₎ of> 5 (with

where I (hki) is the measured intensity of the peak (hkl), I ° ( _hk i) 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 evaluated were: (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. In this case, the "focal plane" is determined by the main extension surface of the focal track, and if the focal plane is curved (which is the case, for example, in the case of a frustoconical running track), then the reference point is present in the respective measuring or reference point of the track

Main extension surface of the same reference. 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. Of the

Recrystallization rate in turn increases with increasing temperature and with increasing duration of 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, according to this

Continuing specified ranges of texture coefficients is the section of the

Burning web in a non-recrystallized structure or in a partially recrystallized structure with a relatively low degree of recrystallization before. It was found that within these ranges the advantageous properties explained above (high hardness,

Fine Grain) of the focal path can be achieved, 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 ( ₂ oo) of> 6. Is the

Forming degree lower (for example, only in the range of 20% - 30% (total) degree of deformation of the X-ray rotary anode), as well as the above preferred texturing are less pronounced. According to a development, the section of the focal track perpendicular to the focal plane has a texture coefficient T 222) of> 3.3 and / or a texture coefficient TC ( ₂₀ o ₎ of> 4, the range of these lower

Limits is approached, especially at relatively low degrees of deformation.

Tungsten and tungsten based alloys have a cubic centered

Crystal structure on. 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 Γ ^00Ϊ 1 [010], [002], [200] and [100] (in each case based on a cubic-centered unit cell). 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 ( ₂ 22) was 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 ( ₂ oo) determined therefrom, is a measure of the preferential texturing of the <001> direction.

The texture coefficient was calculated according to the following formula:

eg for TC ₍₂₂₂₎ : In this case, I ( _hk i) determines the intensity determined by XRD measurement

Peaks (hkl) at which the texture coefficient TC (hki) is to be determined. The "specific intensity" of a peak (hkl) is in each case the maximum of the relevant one

Peaks (hkl), as recorded in the XRD measurement. In the determination of the respective texture coefficient T hki), in the sum of I _j (hki) from j = 1 to n, the following intensities of the peaks determined by XRD measurement (110), (200), (211), (220 ), (310), (222), and (321) (ie: n = 7). I ° _(hk i ₎ denotes the (normally normalized) texture-free intensity of the relevant peak (hkl) at which the texture coefficient TC (hki) is to be determined. This texture-free intensity would be present if the material in question has no texturing. In

in the same way, in the sum of I ° _j (hki), from j = 1 to n, the texture-free ones become

Summed intensities of these seven peaks. 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 1 1, 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 are used to determine the intensities of the different peaks

X-ray diffraction described. First, the focal point is ground so that the area of the forging zone (upper portion of the focal point, in the forging process in direct contact with the forging tool or in close proximity to the

Forging tool was removed), provided this was completed

X-ray rotary anode has not been completely 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). During the presentation of 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, Cu-Kal radiation with a wavelength of 1.4506 Å was used. The additional effects which occur due to the additionally present Cu-Ka2 radiation in the received 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 made with a Bragg Brentano diffractometer "D4 Endeaver" from Bruker axs with a theta-2 theta diffraction geometry, a Gobel mirror and a Sol-X detector As known in the art, however, also another device with corresponding

Settings are used in such a way 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 are the formula for determining the texture coefficient

Sample preparation and the measurement method applicable accordingly. 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 carrier body was the Powder Diffraction File (German: powder diffractometry data) for molybdenum

(JCPDS No. 00-042-1120). 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 development is at the portion of the focal path perpendicular to the

Focal plane level following relationship of the determinable by X-ray diffraction

Texture coefficient T satisfies:

This ratio describes how much the peak (222) widens or

smeared. 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 conventional X-ray rotary anodes produced in powder metallurgy. 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 a low degree of deformation, however, this ratio can 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 a high hardness is in particular with respect to the avoidance of roughening and / or deformation of the focal track over the

Useful period of time advantageous. 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 Lastaufbringzeit and duration of action may be particularly in molybdenum and

 Molybdenum-based alloys affect the obtained reading. The hardness measurement (both in the focal path and in the support body) is in particular at a radial, perpendicular to the focal plane extending cross-sectional area of

X-ray rotary anode performed.

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 are in the

Partially recrystallized structure formed by Kornneubildung crystal grains surrounded by a forming structure and these crystal grains have, based on a

 Cross-sectional area through the partially-recrystallized structure, an area ratio in the range of 10% to 80%, in particular in a range of 20% to 60%. Within these ranges, and especially within the narrower range, good properties of the focal track with regard to their surface condition and dose yield, even over a long time, could be achieved

Mission durations, achieved. That for the specified range of values

Applicable methods for determining the area ratio will be explained with reference to the figures (see in particular figure description to the figures 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 formed by grain regeneration) is <80%, in particular <60%. According to a development, the section of the focal track has a middle

Small angle grain boundary distance of <10 μπι on. Here is the middle one

Small angle grain boundary distance determinable by a measuring method,

wherein at a radial, perpendicular to the focal plane plane extending cross-sectional area in a region of the portion of the focal track grain boundaries, grain boundary sections and Small angle grain boundaries can be determined with a grain boundary angle of> 5 °, for the determination of the average small-angle grain boundary distance parallel to the

Focal plane into the thus obtained grain boundary pattern a, parallel to the

Cross-sectional area extending Linienschar from each parallel to the focal plane extending lines that each have a distance of 17.2 μπι each is placed on the individual lines respectively the distances between each two mutually adjacent intersections of the respective line with lines of Grain boundary pattern are determined and the average of these distances is determined as a mean low-angle grain boundary distance parallel to the focal plane,

for determining the average small-angle grain boundary distance perpendicular to the

 Concentration level in the obtained grain boundary pattern a, parallel to the cross-sectional area extending line of each perpendicular to the focal plane extending lines, each having a distance of 17.2 μιη each, is placed on the individual lines in each case the distances between in each case two mutually adjacent intersections of the respective line are determined with lines of the grain boundary pattern and the average of these distances is determined as average small-angle grain boundary perpendicular to the focal plane, and the average small-angle grain boundary distance as geometric mean of the mean small-angle grain boundary distance parallel is determined to the focal plane and the average Kleinwinkel-Komgrenzenabstandes perpendicular to the focal plane. Further details on the implementation of the measuring method are given in the description of FIGS. 4A-4D. Such a fine-grained structure, which has a mean low-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 Kleinwinkel-Komgrenzenabstand can be achieved. In particular, the average small-angle grain boundary distance is according to a development <5 μπι. At a low degree of deformation of the X-ray rotary anode, the small-angle grain boundary distance is slightly higher. In particular, it is according to a development <15 μπι, and even this higher limit is even lower than the corresponding value in conventional powder metallurgically produced in combination X-ray rotary anodes.

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

 The focal plane plane relative to the preferential texturing of the <111> direction and the <001> direction can be estimated by means of an EBSD (Electron Backscatter Diffraction) analysis. About the EBSD analysis can

Preferential texturing and EBSD texture coefficients are determined both in directions parallel to the focal plane and perpendicular to the focal plane, for which only a sample surface (eg a cross-sectional area, as shown in Fig. 3) must be examined , The sample preparation and the measuring method will be explained generally with reference to Figs. 4A-4D, with no consideration of the details for determining the EBSD texture coefficient (in particular, the accurate processing of the measured values). Even without specifying the exact determination method of the EBSD texture coefficients can be calculated from the comparison of the different

EBSD texture coefficients Information about the characteristics of the preferred texturing in the different directions (perpendicular and parallel to the focal plane) can be obtained. 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 was an EBSD texture coefficient of 2.5 in the radial direction (RD) for the <110> direction and an EBSD texture coefficient of 2 in the tangential direction (TD) for the <110>direction; 2 determined. 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

Burning web and / or the carrier body has a relative density of> 96%, in particular of> 98%, (relative to the theoretical density), which is particularly advantageous in terms of material properties and 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 shown that a carrier body with these characteristics in comparison to carrier bodies with recrystallized structure, especially at high mechanical loads, a high stability against macroscopic

Having deformations. Such support bodies are particularly well-suited for actively cooled X-ray rotary anodes in which, due to the active cooling, the temperature of the

 Carrier body (or at least large portions thereof) can be maintained in a region below the recrystallization threshold. 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 results for a person skilled in the art, as in the respective composition of the carrier body, the parameters of powder metallurgy production (in particular the temperature during forging, degree of deformation during forging, temperature during the heat treatment, duration of

Heat treatment) in order to obtain the features specified in relation to the carrier body in at least a portion thereof. With "section" of the

Carrier body is particularly referred to a macroscopic contiguous portion (i.e., comprising a plurality of grain boundaries and / or grain boundary portions) 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 training is that classic materials and

Material combinations can be used for the carrier body, which is particularly advantageous in terms of manufacturing costs and costs. 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 alloying constituents (apart from impurities by, for example, oxygen) are formed by 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 development that will

Carrier body material formed by a designated as TZM molybdenum alloy, which is specified in the standard ASTM B387-90 for powder metallurgy production. Specifically, 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 - Share of

0.010-0.040 wt% (C: carbon), an O content of less than 0.03 wt% (O:

Oxygen), and the remaining portion (apart from impurities) Mo

(Mo: molybdenum) on. 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 a good heat conduction and in the

Handling during production very well proven. According to a development, the portion 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

The preferred texturizations given above are set accordingly in the forging process, as explained above with respect to the focal path. They will with

increasing degree of recrystallization again reduced. 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), as in the case of the respective composition of the carrier body

Parameters of the powder metallurgical manufacture must choose the specified

To obtain preferential texturing in at least a portion of the carrier body. According to a development, the section of the carrier body perpendicular to the focal plane, a preferred texturing of the <111> direction with a determinable by X-ray diffraction texture coefficient TC ( ₂ 22) of> 5 and the <001> direction with a over X-ray diffraction determinable texture coefficient TC ( ₂ oo) of> 5. According to a further development, these texture coefficients TC ( ₂₂ 2) and TCpoo _{) are} each at least> 4 (the region directly above this low limit value can be achieved, in particular with 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 ( ₂₀ o _{) 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 is the

Force usually in essence parallel to the (future)

Rotation symmetry axis of the X-ray rotary anode. If the focal plane is substantially planar, this symmetry is maintained. If, on the other hand, the focal plane is not plane, but, for example, frusto-conical (cf., for example, FIG. 3), then the outer, circumferential section is usually turned by a desired angle (for example in the region of 8 °) into or within the context of the forging process. 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 is still on the

Focal plane (or on the interface between the focal and carrier body) reference. Due to the described change in shape in the case of an angled focal length, 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 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 in accordance with one or more of the developments and / or variants explained above, in an X-ray tube for generating X-radiation.

The present invention further relates to a method for producing a

The invention relates to an X-ray rotary anode according to the invention, optionally formed according to one or more of the developments and / or variants described above, the method 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 one on which Carrier portion formed focal length of tungsten or a tungsten-based mixture;

 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, 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) 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 is 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 1,300 - 1,500 ° 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%. The force effect on

Forging takes place in particular parallel to the rotational axis of symmetry of the

X-ray rotating anode, which is exactly or substantially perpendicular to the / the

Focal plane (s) is aligned. 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.

Further advantages and expediencies of the invention will become apparent from the

following description of embodiments with reference to the accompanying figures. From the figures show:

 Fig. 1 A-1C: schematic representations to illustrate different

 Rekristallisationsgrade;

2 shows a schematic diagram for illustrating the hardness curve in FIG

 Dependence on the temperature of a heat treatment;

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

 FIGS. 4A-4D: a schematic representation for illustrating an EBSD analysis; 5A-5C show inverse pole figures 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 means of CVD; and FIG. 7 shows an inverse pole figure of one applied by vacuum plasma spraying

 Burning track.

The following explanation of FIGS. 1A-1C and 2 shows criteria by means of 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. Shown schematically in FIGS. 1A-1C are (greatly enlarged) structures, as can be represented, for example, in an electron micrograph of a correspondingly 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 will be explained with reference to FIGS. 4A to 4D. 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. This is a

Indicate the minimum rotation angle from which a grain boundary is drawn. In FIGS. 1A to 1C (apart from the detail shown separately in FIG. 1B), it is assumed that a minimum angle of rotation of 15 ° was specified, so that the course of the large-angle grain boundaries (or grain boundary sections) can be seen. In Fig. 2, starting from an initial hardness -AH-, in the context of

powder metallurgical production is obtained 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 carried out over a predetermined period -t-, such as over a period of one hour, shown. If the heat treatment is carried out for a longer, predetermined period of time, the stage shown in FIG. 2 shifts to the left (ie to lower temperatures), whereas it shifts to the right (ie to higher temperatures) for a shorter period of time ,

In Fig. 1 A is a pure forming structure, as for example after a

Forging process (which is carried out in the context of powder metallurgical production) is obtained shown. As 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) Displacements -4-, which are represented by the symbol "J" in Figs.1A and 1B, and new grain boundary portions -2- The original grains of the sinter, if still recognizable, are strongly crushed due to the deformation and Furthermore, the forming structure has a substructure that can be visualized in the context of an EBSD analysis of the respective ground surface when a smaller minimum rotation angle is set This Substructure of the forming structure is below

Referring to 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 increasingly small angle grain boundary sections 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 operations, for example, on a

Disappearance and / or order of dislocations are recognizable, is none

Activation energy required. These recovery processes lead to a decrease in hardness. In this region -EH- of the recovery processes (range up to Ti in Fig. 2), the hardness decreases continuously with increasing temperature, the slope in this range -EH- is relatively flat (see Fig. 2). Above a certain temperature -Ti, the activation energy required for grain regeneration during recrystallization can be applied. This temperature T _\ - depends inter alia on the composition and the degree of deformation of the shift structure as well as on the duration of each heat treatment performed. 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, 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) surrounding) portion of the partially recrystallized structure is still present 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 illustrated 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, by Kornneubildung originated

Crystal grains -6- are free from the structure. In the inventive

X-ray rotary anode is the substructure -9- formed the forming structure, in particular fine-grained.

With increasing recrystallization, which increases with the temperature (and time) of the heat treatment, the hardness decreases sharply (see Fig. 2). In FIG. 2, starting at the temperature -T, the previously flat-falling graph transitions into an area with a steeply sloping slope. The transition region between the shallow sloping portion and the steeply sloping portion of the graph, in particular the point with the highest curvature, is called the recrystallization threshold -RKS- (see Fig. 2). With increasing

Recrystallization increase the, by grain regeneration already formed crystal grains, it form by Kornneubildung further crystal grains and the

Forming structure disappears increasingly. In particular, the forming structure is increasingly "consumed" by the crystal grains formed by grain regeneration

Kornneubildung resulting crystal grains together and finally (at least largely) also fill the remaining spaces. In this stadium

Crystal growth slows down again and in FIG. 2 the slope of the graph flattens 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 corresponds to -T ₂ - (in Fig. 2, the duration of the heat treatment is one hour), is defined so that after a heat treatment of one hour at this recrystallization, the recrystallization is 99% complete. The area -RK-, the temperature of the -TI- starting up to the recrystallization temperature T _2, - extends is referred to as recrystallization, as in the same run to a considerable extent recrystallization. Finally, the graph goes into an area -EB-, in which it no longer or only very flat drops. Grain growth still occurs in this area, but it does not find any

Recrystallization or only a recrystallization to a very small extent (in particular the remaining one percent of the structure) instead. In Fig. IC, an idealized, fully recrystallized structure is shown. The

Grain boundaries of the crystal grains formed by grain remodeling directly adjoin one another. The original forming structure has completely disappeared. In this case, the "ideal case" of a completely recrystallized structure is shown in FIG

Grain boundaries each adjacent to each other along their entire extension direction.

In Fig. 3, the structure of a Röntgendrehanode -10- is shown schematically, the

is formed rotationally symmetrical to a rotational symmetry axis -12-. 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 carrier 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 external shape and structure of the

X-ray rotary anode -10- may differ from the illustrated X-ray rotary anode as is known in the art. As can be seen with reference to FIG. 3, the

(macroscopic) proportion of non-recrystallized and / or partially recrystallized structure (both in the focal path as well as in the support body) are generally determined by one, radial (ie through the axis of rotation symmetry -12- running) and is examined perpendicular to the focal plane plane cross-sectional area then, which areas in a non-recrystallized and / or in a partially-recrystallized

Structure available. Hereinafter, with reference to FIGS. 4A to 4D, one with a

 Scanning electron microscope feasible EBSD analysis (EBSD: Electron Backscatter Diffraction). Within the framework of such an EBSD analysis, a characterization of the respective structure can be carried out on a microscopic level. In particular, in the context of such an EBSD analysis, the fineness of the respective structure can be determined, the occurrence and extent of substructures determined, the proportion of crystal grains formed by grain regeneration in one

partially recrystallized structure as well as occurring in the structure preferential texturing can be determined. For this purpose, in the context of the sample preparation, a cross-sectional area extending radially and perpendicular to the focal plane (corresponding to the cross-sectional area shown in FIG. 3) is produced by the X-ray rotary anode. The preparation of a

In particular, the corresponding surface is made by embedding, grinding, polishing and etching at least a portion of the obtained cross-sectional area of the X-ray rotary anode, the surface is still ion-polished (to remove the process caused by the grinding deformation structure on the surface). 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 information in parentheses refers to those of the

Applicant used device types, which in principle also other types of devices that allow the described functions, can be used in a corresponding manner. The acceleration voltage is 20 kV, it is set a 50-fold magnification and the distance of the individual pixels on the sample, which are scanned sequentially, is 4 μπι. The individual pixels 17 are arranged relative to one another in equilateral triangles, the side length of a triangle corresponding in each case to the grid spacing -18- of 4 μπι (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

(Nanometer) and has a depth of 50 nm. The representation of the information of a pixel is then in the form of a hexagon -19- (shown in phantom in FIG. 4A), the sides of each of which the bisectors between the respective pixel -17- and the respective nearest (six) pixels -17- form. The examined sample surface -21- is in particular 1,700 μιη times 1,700 μπι. As shown in FIG. 4B, in the present case, in an upper half, it comprises a focal length section -22- (in cross-section) of approximately 850 times

1.700 μπι and in the lower half of a carrier body portion -24- (in cross section) of about 850 times 1700 μπι ^second 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- (each parallel to their sides). Further, it is parallel to the radial direction -RD- (see, e.g., direction -RD- in Fig. 3, 4B). As explained above with reference to FIG. 4A, the examined sample surface -21- is scanned with a grid of 4 μm.

For the determination of the mean grain boundary distance (or small angle grain boundary distance), within the EBSD analysis, grain boundaries and

Grain boundary sections with a grain boundary angle greater than or equal to one

Minimum rotation angle is visible within the examined sample area -21-. In the present case, a determination is made of the mean grain boundary distance

Minimum rotation angle of 15 ° set in the scanning electron microscope. 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 in a direction perpendicular to the

Focal plane level down towards. 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-. Due to 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 investigated sample surface, grain boundaries or grain boundary sections are always determined and displayed between two halftone dots -17- by the scanning electron microscope, if between the two halftone dots -17-

Orientation difference of the respective lattice of> 15 ° is determined (if another minimum rotation angle is set, then the latter is decisive). When

Orientation difference is used in each case the smallest angle that is required to merge the respective crystal lattice, which are present at the respective, to be compared halftone dots -17-, into each other. This process is performed at each grid point -17- with respect to all grid points surrounding it (i.e., each with respect to six surrounding grid points). In Fig. 4A, a grain boundary portion -20- is exemplified. In this way, within the examined sample surface -21-

Grain boundary pattern -32-, which in the case of a partially recrystallized structure (at a

Minimum rotation angle of 15 °) through grain boundary sections and circumferential

Grain boundaries is formed, obtained. This is shown schematically in FIGS. 4C and 4D for a section of the focal track. 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 not shown in FIGS. 4C and 4D).

The determination of the mean grain boundary distance of the

Corrugated material explained in parallel to the focal plane. In order to determine the grain boundary distance of the material of the track material, only the focal point segment-22- of approximately 850 times 1700 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 determined. For this purpose, within the investigated sample surface -21- (which has an area of 1,700 × 1,700 μm ² ) into the grain boundary pattern -32-, there is a family of 98 lines each having a length of 1,700 μm and a relative spacing of 17.2 μπι (1,700 μιη / 99) laid. In Fig. 4C, this is schematic for one within the examined

Brennbahnabschnittes -22- located cutting -28- of the focal point shown. The

Liner -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 grain boundary pattern -32- as a half crystal grain. The frequency of the different distances, which were determined within the focal section -22- (about 850 x 1,700 μπι ² ) is evaluated and then an average of the distances 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 average grain boundary distance perpendicular to the

Focal plane, i. along the direction -ND-, takes place within the

Corrugated track 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 average 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:

In a similar way, the determination of the mean

(Small angle) grain boundary distance of the section of the focal track parallel and perpendicular to the focal plane, with 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 ° are additionally taken into account the small angle grain boundaries of the substructure (which is present in the Umformstruktur). 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, as shown schematically in FIGS. 1A-1C, for example, the area fraction of the crystal grains formed by grain regeneration (relative to FIG

Total area of the examined section). This determination can again be made with a scanning electron microscope in the context of an EBSD analysis. In this regard, reference is made to the measuring arrangement and sample preparation explained above with reference to FIGS. 4A to 4D and the illustrated measuring method. 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, in particular the circumferential grain boundaries of, resulting from Kornneubildung

Crystal grains and the (large angle) grain boundary sections are determined. 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, by grain regeneration

resulting crystal grains is (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, essentially the course of the curve shown in FIG. 2 can be traced and it can be determined in which region of the curve the respective sample is located. As explained above, is preferably within the

Area ~ TB- worked around the recrystallization threshold -RKS- (wherein the area -TB- in Fig. 2 by the dashed circle around the recrystallization threshold -RKS- is shown schematically).

In the context of determining the degree of recrystallization, it is generally to be taken into account that for certain materials (for example, molybdenum and molybdenum alloys) pronounced recovery processes take place. 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 in FIG. 2 already falls more sharply in the area of the recovery processes -EH- and the

Recrystallization threshold can shift towards 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 qualitatively a deviation, as shown schematically in Fig. 2 by the dashed line. In molybdenum-based alloys, this effect is additionally superimposed by the formation of particles, which is also on the concrete

Curve can affect. Qualitatively, the curve is always in the

Essentially, as shown in Fig. 2.

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 as 0.03% by weight of oxygen and the remaining portion of molybdenum (after completion of all, within the framework of

powder metallurgical production carried out heat treatments) is obtained (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. Unless in the context of this embodiment

Good results can be achieved for different combinations within the respective area. While for the

According to the invention properties of the focal track (and essentially also for the described advantageous properties of the carrier body) the specified parameters in the step of pressing and in the step of sintering are less critical, in particular the temperatures in the forging step and in the subsequent Heat treatment on the properties of the focal track (especially on the

Degree of recrystallization). In particular, the preferred

Temperatures at the step of forging and in the step of the subsequent heat treatment (at the preferred specified degree of 60%) achieved particularly good results.

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 carried out at one, extending through the axis of rotation symmetry cross-sectional area. In which

Support body could also R _p 0.2 of 650 MPa (Mega Pascal), and an elongation at break A of 5% can be achieved at room temperature a 0.2% proof stress. 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. In comparison, in conventional,

Powder-metallurgically produced carrier bodies (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 inventive

X-ray anodes significantly higher hardnesses (the focal path and the support body) and higher Dehngrenzen (at least in the carrier body) than in conventional

powder-metallurgically produced X-ray rotary anodes can be achieved. 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). With such "gentle" ductilization (i.e., heat treatment at comparatively low

Temperatures) is achieved at the same time that the structure of the focal zone 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 material 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 could be determined that cracks are deflected along the grain boundaries of the fine - grained structure and thus several times the

Change propagation direction. 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).

To investigate the texture of the focal track and the carrier body was a

X-ray rotary anode, as explained above with reference to Figures 4A to 4D, prepared as a sample to be examined. The X-ray rotary anode was included

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, under

With reference to Figures 4A to 4D used explained settings, provided that they are applicable to determine the texture or make. The under the

EBSD analysis of the track obtained inverse pole figures are shown in Figs. 5A-5C. 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 are substantially radially and parallel to the

Trajectory level extends as well as -TD-, which runs tangentially and parallel to the focal plane, defined (these directions are shown for the sake of illustration in Fig. 3). The force of the forging operation during the manufacturing process of the associated X-ray rotating anode was perpendicular to the focal plane (i.e., along the -ND- direction). In Fig. 5A, the inverse pole figure of the focal track is in the direction -ND-, in Fig. 5B the inverse pole figure is in direction -RD- and in Fig. 5C the inverse pole figure is shown in the direction -TD-. With reference to Fig. 5A, the pronounced preferential texturing of the <111> direction and the <001> direction along the direction -ND- can be seen. Furthermore, with reference to FIGS. 5B and 5C, the (less pronounced) preferred texturing of the <101> direction along the directions -RD- and -TD- can be recognized. 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 -ND direction as well as a (somewhat less pronounced) preferential texturing of the <101> direction along the

Directions -RD- and -TD- measured. For comparison, correspondingly prepared samples of a tungsten-refractory track (see Fig. 6) applied by CVD method and a focal track produced by vacuum plasma spraying (see Fig. 7) were made of a tungsten-rhenium alloy (tungsten content: 90% by weight, rhenium content: 10% by weight) in terms of texture. In FIG. 6, the inverse pole figure in the direction of -TD- is shown. As can be seen from FIG. 6, the CVD coating has a preferred texturing of the <111> direction along the direction -TD-. In Fig. 7, the inverse pole figure in the direction -ND- is shown. As can be seen from FIG. 7, the focal path produced by vacuum plasma spraying has pronounced preferential texturing of the <001> direction along the direction ND-.

Claims

 claims

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 powder metallurgically produced in the composite, the carrier body (14) of molybdenum or a molybdenum-based alloy is formed, and the focal lane (16) of tungsten or a

Tungsten-based alloy is formed,

characterized,

in 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.

X-ray rotary anode according to claim 1, characterized in that the section 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 with an X-ray diffraction determinable texture coefficient TCpoo) of> 5.

X-ray rotary anode according to claim 1 or 2, characterized in that at the portion of the focal track (16) perpendicular (ND) to the focal plane level following relationship of the X-ray diffraction determinable texture coefficients T ₂₂₂ ) and TC ₍ 3io) e

X-ray rotary anode according to one of the preceding claims, characterized

characterized in that the portion of the focal track (16) has a hardness of> 350 HV 30. X-ray rotary anode according to one of the preceding claims, characterized

characterized in that the portion of the focal track (16) is present in a partially recrystallized structure.

X-ray rotary anode according to claim 5, characterized in that in the

crystal grains (6) formed by partially recrystallized structure are surrounded by a reforming 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 a middle one

Small angle grain boundary distance of <10 μιη has,

 wherein the average small-angle grain boundary distance can be determined by a measuring method in which grain boundaries (8), grain boundary sections (2) and small-angle grain boundaries (B) are formed at a radial cross-sectional area perpendicular to the focal plane in a region of the section of the focal path (16). 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 from each other 17.2 μιη, is placed on the individual lines in each case the distances between in each case two mutually adjacent points of intersection of the respective line with lines of the grain boundary pattern (32) are determined and the mean value of these distances as a mean small-angle grain boundary distance parallel to the focal plane Level is determined

for determining the average small-angle grain boundary distance perpendicular to the focal plane in the obtained grain boundary pattern (32), a parallel to the cross-sectional area extending line (36) from each perpendicular to the focal plane extending lines, each with a distance of 17 each , 2 μηι, is placed, at the individual lines in each case the distances between two mutually adjacent intersection points of the respective line with lines of the grain boundary pattern (32) are determined and the average of these distances is determined as a mean small-angle grain boundary distance perpendicular to the focal plane, and

 the mean small-angle grain boundary distance 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 level is determined.

8. X-ray rotary anode according to one of the preceding claims, characterized

 characterized in that the portion of the focal track (16) in directions parallel to the focal plane (RD, TD) has preferential texturing of the <101> direction.

9. X-ray rotary anode according to one of the preceding claims, characterized

 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.

10. X-ray rotary anode according to claim 9, characterized in that the portion of the carrier body (14) has a hardness of> 230 HV 10.

11. X-ray rotary anode according to claim 9 or 10, characterized

 - That the portion of the support body (14) perpendicular (ND) to the

 Focal plane has preferential texturing of the <111> direction and the <001> direction; and or

 in that the section of the carrier body (14) in directions (RD, TD) parallel to the focal plane has a preferred texturing of the <101> direction.

12. X-ray rotary anode according to one of claims 9 to 11, characterized in that the portion of the carrier body (14) at room temperature an elongation at break of

> 2.5%. 13. 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 alloy 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.

14. Use of an X-ray rotary anode (10) according to one of the preceding claims in an X-ray tube for generating X-radiation.

15. A method for producing an X-ray rotary anode (10) according to any one of claims 1 to 13, comprising the following steps:

 A) Providing a by pressing and sintering of appropriate

 Starting powders in the composite produced starting body with a carrier body portion of molybdenum or a molybdenum-based mixture and formed on the carrier body portion focal length of tungsten or a tungsten-based mixture;

 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 the final heat-treated one

 X-ray rotary anode (10) at least a portion of the focal path (16) obtained from the focal length section in a non-recrystallized and / or in one

 partially recrystallized structure is present.

16. The method according to claim 15, characterized in that the heat treatment at temperatures in a range of 1,300 - 1,500 ° C is performed.

17. The method according to claim 15 or 16, characterized in that the forged body after completion of the forging has a degree of deformation in the range of 20% to 60%.