CN112142467A - Al (aluminum)2O3EAG eutectic ceramic and preparation method thereof - Google Patents
Al (aluminum)2O3EAG eutectic ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention provides Al2O3An EAG eutectic ceramic and a preparation method thereof, belonging to the technical field of directional solidification eutectic ceramic preparation. The invention discovers that the size of the solidification rate is related to the temperature gradient for the first time, and for a specific temperature gradient delta G, the larger the solidification rate is, the finer the lamella is, and the influence of the solidification rate on the eutectic ceramic structure is revealed. The invention accurately controls the solidification rate (5-40 mm/h) and the temperature gradient (10)3K/cm) to avoid the generation of cellular crystals or coarse EAG phases, thereby improving Al2O3The mechanical property of the/EAG eutectic ceramic provides guidance for preparing high-performance eutectic ceramic.
Description
Technical Field
The invention relates to the technical field of preparation of directional solidification eutectic ceramics, in particular to Al2O3An EAG eutectic ceramic and a preparation method thereof.
Background
The directional solidification oxide eutectic composite material has higher melting point and low density<5g/cm3) And excellent high-temperature strength (13 times that of the same-component sintered material), and the high-temperature strength is not reduced by the propagation of sub-cracks. In addition, the eutectic structure is excellent in heightThe temperature stability, the structure is stable when the temperature is close to the melting point, the coarsening cannot occur, and the high-temperature oxidation resistance and the hot corrosion resistance are good. By virtue of the excellent comprehensive performance, the directional solidification oxide eutectic composite material is widely noticed and is considered as a turbine blade structural material in a new generation high-temperature (1973K) working environment.
Because the melting point of the alumina-based eutectic ceramic is extremely high, the aluminum-based eutectic ceramic is difficult to prepare by using the traditional directional solidification method (the traditional method and equipment cannot reach the melting point of the alumina-based eutectic ceramic). Therefore, the development of a new preparation technology is urgently needed. The optical suspension zone melting method is a new method capable of preparing large block oxide eutectic, can prepare test bars with the maximum diameter of about 15mm and the maximum length of about 140mm under the condition of not using a crucible, and has high temperature gradient (about 10)3K/cm) without pollution, the adjustable range of the growth rate is wide (5 mm/h-180 mm/h), and the tissue structure can be controlled to obtain the eutectic ceramic with excellent performance. According to the Hall-Petch relationship (the Hall-Petch relationship sigma is sigma)0+kd^(-1/2)Where σ represents yield stress, d represents the lamella spacing, and σ represents0And k represents a constant related to the type of crystal) it is known that the finer the lamella is, the better the properties of the ceramic are. However, the solidification of ceramics is different from the solidification of metals, the thermal shock resistance of ceramics is poor, and the rapid solidification can cause not only common thermal shock cracks but also structural defects caused by undercooling of components and the like, so that the mechanical properties of the existing eutectic ceramics can not meet the use requirements.
Disclosure of Invention
The invention aims to provide Al2O3Eutectic ceramic/EAG (aluminum oxide) and preparation method thereof, and Al prepared from eutectic ceramic2O3the/EAG eutectic ceramic has uniform structure and good mechanical property.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides Al2O3The preparation method of the/EAG eutectic ceramic comprises the following steps:
mixing the mixed raw material powder with a ball-milling solvent, and performing ball milling, drying, pressing and sintering in sequence to obtain a prefabricated member;
directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al2O3a/EAG eutectic ceramic;
the mixed raw material powder is Al2O3And Er2O3In the mixture of (1), Al2O3And Er2O3The mole percentage of (1) is 81: 19;
the solidification rate of the directional solidification is 5-40 mm/h, and the temperature gradient is 103K/cm。
Preferably, the ball milling time is 5-8 h, and the rotating speed of the ball milling is 300-600 r/min; the drying time is 18-48 h.
Preferably, the pressing comprises dry pressing and cold isostatic pressing performed in sequence.
Preferably, the pressure of the dry pressure is 30-50 MPa, and the pressure of the cold isostatic pressing is 220-280 MPa.
Preferably, the sintering temperature is 1550 ℃ and the time is 2 h.
Preferably, the preform is subjected to a rotary preheating before the directional solidification, and the rotation speed of the rotary preheating is 15 r/min.
Preferably, the solidification rate of the directional solidification is 20-30 mm/h.
The invention provides Al prepared by the preparation method in the technical scheme2O3the/EAG eutectic ceramic.
The Al is2O3the/EAG eutectic ceramic is made of irregularly arranged Al2O3And EAG in space, the Al2O3the/EAG eutectic ceramic has a three-dimensional communication structure.
The Al is2O3The HV hardness of the/EAG eutectic ceramic is 10-14 GPa, and the fracture toughness is 4-6 MPa.m1/2。
The invention provides Al2O3The preparation method of the/EAG eutectic ceramic comprises the following steps: mixing the mixed raw material powder with a ball milling solvent, and sequentially carrying out ball milling and dryingPressing and sintering to obtain a prefabricated part; directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al2O3a/EAG eutectic ceramic; the mixed raw material powder is Al2O3And Er2O3In the mixture of (1), Al2O3And Er2O3The mole percentage of (1) is 81: 19; the solidification rate of the directional solidification is 5-40 mm/h, and the temperature gradient is 103K/cm. The invention discovers that the size of the solidification rate is related to the temperature gradient for the first time, and for a specific temperature gradient delta G, the larger the solidification rate is, the finer the lamella is, and the influence of the solidification rate on the eutectic ceramic structure is revealed. The invention accurately controls the solidification rate (5-40 mm/h) and the temperature gradient (10)3K/cm) to avoid the generation of cellular crystals or coarse EAG phases, thereby improving Al2O3The mechanical property of the/EAG eutectic ceramic provides guidance for preparing high-performance eutectic ceramic.
Drawings
FIG. 1 shows Al2O3And Er2O3Phase diagram of (a);
FIG. 2 is a schematic view of a light suspension zone furnace used in the present invention;
FIG. 3 shows Al prepared in examples 1 to 82O3Macro topography of the/EAG eutectic ceramic sample rod;
FIG. 4 shows Al prepared in examples 1 to 82O3A longitudinal section morphology diagram of a eutectic structure of the/EAG eutectic ceramic sample rod;
FIG. 5 shows Al prepared in examples 1 to 82O3A cross-sectional morphology diagram of a eutectic structure of the/EAG eutectic ceramic sample rod;
FIG. 6 shows Al prepared in example 42O3XRD pattern of/EAG eutectic ceramic sample bar;
FIG. 7 shows Al prepared in example 42O33D space structure morphology graph (a) of/EAG eutectic ceramic sample rod and Al2O3Three-dimensional structure of (a), three-dimensional structure of (c) and three-dimensional distribution and frequency map of different diameter microwells (d);
FIG. 8 is a drawing showing a preparation of example 4Prepared Al2O3And (3) a crack propagation topography of the/EAG eutectic ceramic sample bar.
Detailed Description
The invention provides Al2O3The preparation method of the/EAG eutectic ceramic comprises the following steps:
mixing the mixed raw material powder with a ball-milling solvent, and performing ball milling, drying, pressing and sintering in sequence to obtain a prefabricated member;
directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al2O3a/EAG eutectic ceramic;
the mixed raw material powder is Al2O3And Er2O3In the mixture of (1), Al2O3And Er2O3The mole percentage of (1) is 81: 19;
the solidification rate of the directional solidification is 5-40 mm/h, and the temperature gradient is 103K/cm。
In the present invention, unless otherwise specified, all the starting materials required for the preparation are commercially available products well known to those skilled in the art.
According to the invention, mixed raw material powder and a ball-milling solvent are mixed, and ball-milling, drying, pressing and sintering are sequentially carried out to obtain a prefabricated member. In the present invention, the mixed raw material powder is Al2O3And Er2O3The mixture of (1), the Al2O3The purity of (b) is preferably 99.95%; the Er2O3The purity of (b) is preferably 99.99%. In the present invention, the Al2O3And Er2O3The particle size of (a) is preferably in the micron order; the invention aims at the micron-sized Al2O3And Er of micron order2O3The specific particle size of (b) is not particularly limited, and commercially available powders known in the art may be used.
In the present invention, the Al2O3And Er2O3In the mixture of (1), Al2O3And Er2O3The mole percentage of (1) is 81: 19; the invention is preferably based on Al2O3And Er2O3Phase diagram of (as shown in FIG. 1) to determine Al2O3And Er2O3The eutectic is ensured to occur under the condition of the mole percentage, so that the eutectic ceramic is prepared.
In the present invention, the ball milling solvent is preferably ethanol, and the ethanol is preferably analytically pure absolute ethanol; the amount of the ball milling solvent used in the present invention is not particularly limited, and ball milling can be smoothly performed according to the amount well known in the art.
In the present invention, the mixing process of the mixed raw material powder and the ball milling solvent and the ball milling process are preferably performed in a planetary ball mill, and the type of the planetary ball mill is not particularly limited in the present invention, and any planetary ball mill known in the art may be used. In the invention, the ball milling time is preferably 5-8 h, and more preferably 6-7 h; the rotation speed of the ball milling is preferably 300-600 r/min, and more preferably 400-500 r/min.
After the ball milling is completed, drying the obtained ball milling material, wherein the drying time is preferably 18-48 h, and more preferably 24-36 h; the drying temperature is preferably 50-80 ℃, and more preferably 60-70 ℃. The drying equipment is not particularly limited in the present invention, and equipment well known in the art may be selected.
After the drying is finished, the obtained dry powder is preferably pressed to obtain a strip sample. In the present invention, the pressing preferably comprises dry pressing and cold isostatic pressing performed in sequence; the pressure of the dry pressure is preferably 30-50 MPa, more preferably 35-45 MPa, and the time is preferably 3-8 min, more preferably 5 min; the pressure of the cold isostatic pressing is preferably 220-280 MPa, more preferably 240-260 MPa, and the time is preferably 20-30 min, more preferably 25 min. The equipment for dry pressing and cold isostatic pressing is not particularly limited in the present invention, and equipment well known in the art can be selected. The invention reduces the air in the sample through cold isostatic pressing and improves the density of the sample. The strip-shaped sample is obtained by pressing, so that the subsequent sintering is facilitated.
The size of the strip-shaped sample is not specially limited, and the strip-shaped sample can be adjusted according to actual requirements; in an embodiment of the present invention, the dimensions of the strip-shaped test specimen are specifically 10mm × 10mm × 100 mm.
After the pressing is completed, the obtained strip-shaped test sample is preferably sintered, wherein the sintering temperature is preferably 1550 ℃ and the time is preferably 2 hours. The sintering is preferably carried out in a sintering furnace, which is not particularly limited in the present invention and is a device well known in the art. 39% (mass fraction) of Al in the sintering process2O3And Er2O3React to form Er3Al5O12(EAG), remainder Al2O3Formation of Al with EAG2O3a/EAG preform; the Al is2O3The amount of (c) is the amount corresponding to the eutectic point determined from the phase diagram. The invention obtains the prefabricated member with certain strength and density through sintering.
After obtaining the prefabricated part, the prefabricated part is directionally solidified in a light suspension zone melting furnace to obtain Al2O3the/EAG eutectic ceramic. The method preferably comprises the steps of chamfering the prefabricated member, cutting out a suspended ditch and then performing the light suspension zone melting experiment process; the chamfering process is not particularly limited in the present invention, and may be performed according to a process well known in the art. In the invention, the heat source of the optical suspension zone melting furnace is preferably a xenon lamp, the power of the xenon lamp is preferably 3kW, the number of the xenon lamps is preferably 4, and the xenon lamps are preferably arranged in the optical suspension zone melting furnace at equal intervals; the present invention does not specifically limit the equal spacing, and it is sufficient to ensure that the xenon lamps are equally spaced in the heating region of the optical suspension zone furnace. According to the invention, the solidification rate can be ensured within the range of 5-40 mm/h by controlling the heat source of the optical suspension zone melting furnace under the above conditions.
In the embodiment of the invention, the directional solidification is carried out in the optical suspension zone melting furnace shown in fig. 2, the optical suspension zone melting furnace comprises an upper shaft 1, a lower shaft 2, a feed rod 3, a seed rod 4, a quartz tube 5, a xenon lamp 6 and an elliptic mirror 7, wherein the upper shaft 1, the lower shaft 2, the feed rod 3 and the seed rod 4 are arranged in the quartz tube 5; the upper shaft 1 is in contact with the feed rod 3, and the upper shaft 1 is used for pushing the feed rod 3; the lower shaft 2 is in contact with the seed rod 4, and the lower shaft 2 is used for pushing the seed rod 4; the xenon lamp 6 and the elliptical mirror 7 are arranged outside the quartz tube 5, and the elliptical mirror 7 surrounds the xenon lamp 6 and is used for changing the light path.
In the present invention, it is preferable to install the preform and Al before performing the directional solidification2O3And (5) seed crystal. The invention utilizes Al2O3The seed crystal provides a center which is easy to grow for the crystal on one hand, and fixes the growth direction for the growth of the single crystal on the other hand, thereby realizing the directional growth of the eutectic ceramic. In the present invention, the process of mounting is preferably to hang the preform on the upper shaft 1 with a nickel wire, and to hang Al on the upper shaft2O3The seed crystal is fixed on the lower shaft 2. In mounting the preform and Al2O3During the process of seed crystal, the installation mode is preferably adjusted by rotating the upper shaft 1 and the lower shaft 2 to ensure the prefabricated part and Al2O3The axes of the seed crystals are positioned on a straight line to ensure the success of crystal selection.
Completing the preform and Al2O3After the seed crystal is installed, a heating power supply is preferably started, the temperature is automatically raised, the elliptical mirror 7 is adjusted to change the light path, the light spot of the xenon lamp 6 is ensured to be concentrated at the tip end of the prefabricated part, the prefabricated part is preheated, when the prefabricated part is partially melted to form a liquid drop, the seed crystal rod 4 is lifted upwards to enable the lower end of the prefabricated part melted in the suspension region to be connected with the seed crystal to form the suspension region, the temperature is kept for 1min to stabilize the suspension region, then a drawing system (namely the upper shaft 1, the lower shaft 2 and the feed rod 3) of the optical suspension region melting furnace is started to draw, so that the prefabricated part continuously moves towards the lower shaft 2 until the whole prefabricated part is completely melted, and continuously moves downwards, and the prefabricated part is solidified after being far away from a heat source.
In the invention, before directional solidification, the inside of the quartz tube 5 is wiped clean, so that the situation that the quartz tube blocks a light source to cause difficulty in melting the prefabricated part is avoided.
In the invention, in order to ensure the stability of the suspension zone, the lower shaft 2 is preferably rotated clockwise, and the rotation speed is preferably 15 r/min; or the upper shaft 1 and the lower shaft 2 do not rotate.
In the invention, the solidification rate of the directional solidification (namely the drawing rate of the drawing system) is 5-40 mm/h, preferably 20-30 mm/h; temperature gradient of 103K/cm. The invention controls the solidification rate by the withdrawal rate of the withdrawal system. The invention finds that the size of the solidification rate is related to the temperature gradient, and for a specific temperature gradient delta G, the larger the solidification rate is, the finer the lamella is, and the invention can avoid the generation of cellular crystals or coarse EAG phases by accurately controlling the solidification rate and the temperature gradient, thereby improving Al2O3Mechanical property of the/EAG eutectic ceramic.
After the directional solidification is finished, the heating is preferably stopped, the obtained material is placed in a quartz tube, cooled to room temperature along with the furnace and then taken out, and the top end of the material can be prevented from generating thermal stress cracks.
The invention provides Al prepared by the preparation method in the technical scheme2O3the/EAG eutectic ceramic.
In the present invention, the Al2O3the/EAG eutectic ceramic is preferably made of irregularly arranged Al2O3And EAG in space, the Al2O3the/EAG eutectic ceramic has a three-dimensional communication structure; the Al is2O3The HV hardness of the/EAG eutectic ceramic is preferably 13.5 +/-0.4 GPa, and the fracture toughness is preferably 5.7 +/-0.3 MPa-m1/2。
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following examples, Al was used2O3Has a purity of 99.95% and a particle diameter of 2-10 μm, and the Er2O3The purity of the particles is 99.99%, and the particle size is 2-10 mu m; the light used is suspendedThe heat source of the zone melting furnace is a xenon lamp, the power of the xenon lamp is 3kW, the number of the xenon lamps is 4, and the xenon lamps are arranged in the light suspension zone melting furnace at equal intervals.
In the following examples, the directional solidification was carried out in particular in a light suspension zone furnace as shown in FIG. 2, the preform being suspended from an upper shaft 1 by means of nickel wire and Al being suspended before the directional solidification2O3Seed crystals are fixed on the lower shaft 2 to ensure the prefabricated part and Al2O3The axis of the seed crystal is positioned on a straight line, then a heating power supply is started, the temperature is automatically raised, the elliptical mirror 7 is adjusted to change the light path, the light spot of the xenon lamp 6 is ensured to be concentrated at the tip of the prefabricated member, and then the preheating and directional solidification processes of the prefabricated member are carried out.
Example 1
Mixing Al2O3And Er2O3Mixture of (mole percent Al)2O3:Er2O381:19) adding analytically pure ethanol, placing the mixture in a planetary ball mill, mixing for 6 hours (the ball milling speed is 400r/min), and placing the obtained mixed material in a drying oven to dry for 24 hours at 60 ℃;
pressing the dried powder under 40MPa for 5min to obtain a sample with the size of 10mm multiplied by 100 mm; carrying out cold isostatic pressing under the pressure of 280MPa, and fully loading for 30min to obtain a strip sample; then sintering the obtained strip sample in a sintering furnace for 2h at 1550 ℃ in an air atmosphere to obtain a prefabricated part;
placing the prefabricated part into a light suspension zone melting furnace, carrying out clockwise rotation preheating according to the speed of 15r/min, when the prefabricated part is partially melted to form a liquid drop, lifting a seed crystal rod 4 upwards to enable the lower end of the prefabricated part melted in the suspension zone to be connected with a seed crystal to form a suspension zone, after heat preservation is carried out for 1min, starting a drawing system (namely an upper shaft 1, a lower shaft 2 and a feed rod 3) of the light suspension zone melting furnace to begin drawing, carrying out directional solidification, and setting the temperature gradient to be 10 according to the drawing speed (namely the solidification speed) of 5mm/h3K/cm, the feeding rod 3 pushes the prefabricated part to continuously move towards the lower shaft 2 until the whole prefabricated part is completely melted, the prefabricated part continuously moves towards the lower shaft 2, and after the prefabricated part is far away from a heat source area formed by the xenon lamp 6, the prefabricated part is condensedSolidifying to obtain Al2O3the/EAG eutectic ceramic.
Example 2
This example differs from example 1 in that: setting the temperature gradient at 10mm/h of draw rate (i.e. solidification rate) to 103K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Example 3
This example differs from example 1 in that: at a withdrawal rate of 20mm/h (i.e.the solidification rate), a temperature gradient of 10 is set3K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Example 4
This example differs from example 1 in that: at a withdrawal rate of 40mm/h (i.e.the solidification rate), a temperature gradient of 10 is set3K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Comparative example 1
This comparative example differs from example 1 in that: setting the temperature gradient at 10 at a draw rate of 60mm/h (i.e.the solidification rate)3K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Comparative example 2
This comparative example differs from example 1 in that: at a draw rate of 80mm/h (i.e.the solidification rate), a temperature gradient of 10 is set3K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Comparative example 3
This comparative example differs from example 1 in that: the temperature gradient is set to 10 at a draw rate of 100mm/h (i.e.the solidification rate)3K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Comparative example 4
This comparative example differs from example 1 in that: at a withdrawal rate of 180mm/h (i.e.the solidification rate), a temperature gradient of 10 is set3K/cm, directional solidification is carried out to obtain Al2O3the/EAG eutectic ceramic.
Performance testing
For Al prepared in examples 1 to 4 and comparative examples 1 to 42O3The structural characteristics of the/EAG eutectic ceramic sample rod are characterized, the mechanical properties are tested, and the test method and the results are as follows.
1) And (3) observing macro morphology: al prepared in examples 1 to 4 and comparative examples 1 to 42O3the/EAG eutectic ceramic sample rod is placed under a body microscope for observing the macroscopic morphology, and the result is shown in figure 3, wherein (a) to (h) are the sample rods obtained under the conditions of different solidification rates. As can be seen from FIG. 3, the inventive method of manufacturing a sample rod having a diameter of about 9mm and a length of 10cm or more by using a light suspension zone furnace can be used. Furthermore, macrocracks appear in the test bars when the solidification rate is more than 60mm/h, while no cracks are evident in the macroscopic test bars when the solidification rate is not more than 60 mm/h.
2) And (3) observing the tissue morphology: the Al prepared in examples 1 to 4 and comparative examples 1 to 4 was cut out by diamond sawing2O3SEM test results of the/EAG eutectic ceramic sample bar are shown in fig. 4 and 5, wherein (a) to (h) are Al obtained under different solidification rate conditions2O3the/EAG eutectic ceramic sample rod.
FIG. 4 shows Al prepared in examples 1 to 4 and comparative examples 1 to 4 at different solidification rates2O3The longitudinal section morphology of the eutectic structure of the/EAG eutectic ceramic can be seen from FIG. 4, when the solidification rate is more than 100mm/h, a banded structure appears along the solidification direction (solidification from left to right), and when the solidification rate is increased to 180mm/h, the banded structure is widened, and the period is about 208 μm. The results show that cellular eutectic appears in the tissue at a solidification rate of 80mm/h, and cellular EAG appears in the local tissue at a solidification rate of 60mm/h (as shown in FIG. 4 (d)), mainly due to local undercooling caused by a higher solidification rate. When the solidification rate is less than 40mm/h, the structure is completely composed of EAG and Al which are irregularly arranged2O3Is composed of the following components, and the light suspension method is used for preparing the directionally solidified Al2O3The solidification rate range of the/EAG eutectic is determined to be 5-40 mm/h.
FIG. 5 shows Al prepared in examples 1 to 4 and comparative examples 1 to 4 at different solidification rates2O3The cross section morphology of the eutectic structure of the/EAG eutectic ceramic can be seen from figure 5, and the Al prepared by the method disclosed by the invention2O3The eutectic lamina distribution of the/EAG eutectic ceramic is uniform, and the lamina distance is reduced along with the increase of the solidification rate.
3) Phase composition observation: al prepared in example 4 was cut out by diamond sawing2O3the/EAG eutectic ceramic sample bar is subjected to XRD test, and the result is shown in figure 6. As can be seen from FIG. 6, the eutectic ceramic sample rod contains only Al2O3And two phases of EAG.
4) And (3) observing three-dimensional morphology features: a sample rod was cut with a diamond saw, and Al prepared in example 4 was subjected to X-ray three-dimensional imaging (XCT)2O3The three-dimensional structure of the/EAG eutectic ceramic sample bar is observed, and the result is shown in FIG. 7 (wherein gray represents Al2O3White for EAG), wherein (a) is Al prepared in example 42O3A 3D space structure morphology graph of the/EAG eutectic ceramic sample rod, wherein (b) is Al2O3And (c) is a three-dimensional structure of an EAG. As can be seen from (a) to (c) in FIG. 7, Al produced by the present invention2O3the/EAG eutectic ceramic has a three-dimensional space communication structure, Al2O3And the EAG are connected and coupled to each other in space to form a whole, and the volume ratio of the two phases is about Al as calculated from (a) in FIG. 72O3EAG is 48:52, which is close to its theoretical value (49: 51).
FIG. 7 (d) shows Al prepared in example 42O3Three-dimensional distribution and frequency diagram of micropores with different diameters in the/EAG eutectic ceramic sample rod. As can be seen from FIG. 7, the micropores were irregular in shape, most (80% or more) were small, and the average equivalent diameter was 4 μm or less; the average pore diameter was about 2.1m, and the porosity was 0.015% (volume fraction).
5) Microhardness and fracture toughness testing: sample rods were cut with a diamond saw and the micro-indentation technique was used to apply to the Al prepared in example 42O3Hardening of/EAG eutectic ceramic sample bar at room temperatureThe degree and fracture toughness were measured at an experimental load of 50N and a saturation time of 15 s. The results showed that the room temperature hardness was 13.5. + -. 0.4 GPa.
In addition, according to the fracture mechanics theory, the material near the indentation generates residual stress due to the instability of the elastoplastic deformation, and the residual stress field strength at the crack tip in the equilibrium state is numerically recorded as the fracture toughness K of the materialICThe expression is as follows:
KIC＝0.016×(E/HV)1/2(p/c3/2) (ii) a Formula (1)
In the formula (1), E is the elastic modulus, HV is the Vickers hardness, p is the load, and c is the half crack length. Calculating Al according to the formula (1)2O3The fracture toughness of the/EAG eutectic ceramic is KIC＝5.7±0.3 MPa·m1/2The results are shown in Table 1, compared with the values reported in the prior art.
TABLE 1 Al prepared in inventive example 42O3Comparison of the Performance of the/EAG eutectic ceramics with that of the prior art
Wherein the reference information in table 1 is as follows:
[1]Y.Waku,N.Nakagawa,T.Wakamoto,H.Ohtsubo,K.Shimizu,Y.Kohtoku,A ductile ceramic eutectic composite with high strength at 1,873K,Nature 389(1997)49-52.
[2]A.Larrea,V.M.Orera,R.I.Merino,J.I.
J.Eur.Ceram.Soc.25(2005) 1419-1429.
[3]H.J.Su,J.Zhang,C.J.Cui,L.Liu,H.Z.Fu,Mater.S3ci.Eng.A479(2008)380-388.
[4]Kaiden H,Durbin SD,YoshikawaA,Lee JH,SugiyamaK,Fukuda T.Model for the microstructure of oxide eutectics and comparison with experimental observations.J Alloys Compd 2002；336:259-64.
[5]J.Y.Pastor,J.Llorca,A.Martín,J.I.
P.B.Oliete,Fracture toughness and strength of Al2O3-Y3Al5O12 and Al2O3-Y3Al5O12-ZrO2 directionally solidified eutectic oxides up to 1900 K,Journal ofthe EuropeanCeramic Society28(12)(2008)2345-2351.
as can be seen from Table 1, Al produced by the present invention2O3The fracture toughness value of the/EAG eutectic ceramic is higher than that of Al reported in the prior art2O3Based on a binary eutectic ceramic.
6) For Al prepared in example 42O3Hardness test was carried out on the/EAG eutectic ceramic, and SEM test was carried out on the tested sample, and the result is shown in FIG. 8.
FIG. 8 shows Al prepared in example 42O3The micro-indentation crack propagation morphology of the/EAG eutectic ceramic, wherein (a) is a crack overall morphology graph with low magnification; (b) and (c) a topographical map of the localized region at high magnification. As can be seen from fig. 8, the crack deflects and propagates along the phase boundary (fig. 8 (b) and (c)), and the crack also splits and bridges, and it is this crack deflection, splitting and bridging that weakens the propagation energy of the main crack, thereby increasing Al2O3Fracture toughness of the/EAG eutectic ceramic material; this is Al prepared by the present invention2O3The fracture toughness of the/EAG eutectic ceramic is higher than that of the prior documents.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. Al (aluminum)2O3The preparation method of the/EAG eutectic ceramic is characterized by comprising the following stepsThe method comprises the following steps:
mixing the mixed raw material powder with a ball-milling solvent, and performing ball milling, drying, pressing and sintering in sequence to obtain a prefabricated member;
directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al2O3a/EAG eutectic ceramic;
the mixed raw material powder is Al2O3And Er2O3In the mixture of (1), Al2O3And Er2O3The mole percentage of (1) is 81: 19;
the solidification rate of the directional solidification is 5-40 mm/h, and the temperature gradient is 103K/cm。
2. The preparation method of claim 1, wherein the ball milling time is 5-8 h, and the rotation speed of the ball milling is 300-600 r/min; the drying time is 18-48 h.
3. The method of claim 1, wherein the pressing comprises dry pressing and cold isostatic pressing in sequence.
4. The production method according to claim 3, wherein the dry pressure is 30 to 50MPa, and the cold isostatic pressure is 220 to 280 MPa.
5. The method of claim 1, wherein the sintering temperature is 1550 ℃ and the time is 2 hours.
6. The method according to claim 1, wherein the preform is subjected to a rotary preheating before the directional solidification, the rotary preheating being performed at a rotation rate of 15 r/min.
7. The preparation method according to claim 1, wherein the solidification rate of the directional solidification is 20-30 mm/h.
8. Al produced by the production method according to any one of claims 1 to 72O3the/EAG eutectic ceramic.
9. Al according to claim 82O3the/EAG eutectic ceramic is characterized in that the Al is2O3the/EAG eutectic ceramic is made of irregularly arranged Al2O3And EAG in space, the Al2O3the/EAG eutectic ceramic has a three-dimensional communication structure.
10. Al according to claim 8 or 92O3the/EAG eutectic ceramic is characterized in that the Al is2O3The HV hardness of the/EAG eutectic ceramic is 10-14 GPa, and the fracture toughness is 4-6 MPa.m1/2。
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