阅读说明：本技术 一种大尺寸Al2O3/LuAG定向凝固共晶陶瓷及其光悬浮区熔制备方法 (Large-size Al2O3LuAG directional solidification eutectic ceramic and light suspension zone melting preparation method thereof ) 是由 王京阳 孙鲁超 孙昊飞 周翠 杜铁锋 吴贞 线全刚 于 2021-07-27 设计创作，主要内容包括：本发明属于定向凝固共晶陶瓷制备技术,特别涉及一种大尺寸Al-(2)O-(3)/LuAG定向凝固共晶陶瓷及其光悬浮区熔制备方法。该陶瓷为含有氧化铝相和镥铝石榴石相的复合材料,其化学式为Al-(2)O-(3)/Lu-(3)Al-(5)O-(12),氧化铝相和镥铝石榴石相的两相比例为二者相图共晶成分点或近共晶成分点；Al-(2)O-(3)/LuAG定向凝固共晶陶瓷由排列不规则的Al-(2)O-(3)和LuAG在空间中相互连通耦合构成,且具有层片状或胞状共晶微观组织形貌。在无需使用坩埚的情况下,Al-(2)O-(3)/LuAG共晶陶瓷制备出最大直径15mm、最大长度140mm的棒材；Al-(2)O-(3)/LuAG共晶陶瓷棒材的H-(V)硬度为13～16GPa,断裂韧性为2～4MPa·m～(1/2)。本发明通过精确控制凝固速率(10～50mm/h),成功制备出硬度、断裂韧性等关键力学性能优于已知同类共晶陶瓷材料的Al-(2)O-(3)/LuAG新型共晶陶瓷材料。(The invention belongs to a preparation technology of directional solidification eutectic ceramics, and particularly relates to large-size Al 2 O 3 LuAG directional solidification eutectic ceramic and a light suspension zone-melting preparation method thereof. The ceramic is a composite material containing an alumina phase and a lutetium aluminum garnet phase, and the chemical formula of the ceramic is Al 2 O 3 /Lu 3 Al 5 O 12 The two-phase proportion of the alumina phase and the lutetium aluminum garnet phase is the eutectic composition point or the near eutectic composition point of the phase diagrams of the alumina phase and the lutetium aluminum garnet phase; al (Al) 2 O 3 the/LuAG directional solidification eutectic ceramic is prepared from irregularly arranged Al 2 O 3 And the LuAG is formed by mutual communication and coupling in space, and has a lamellar or cellular eutectic microstructure morphology. Al without the use of a crucible 2 O 3 /LuAG, preparing a bar with the maximum diameter of 15mm and the maximum length of 140mm by using eutectic ceramic; al (Al) 2 O 3 H of LuAG eutectic crystal ceramic bar V The hardness is 13-16 GPa, and the fracture toughness is 2-4 MPa.m 1/2 . According to the invention, by accurately controlling the solidification rate (10-50 mm/h), Al with key mechanical properties such as hardness, fracture toughness and the like superior to those of the known eutectic ceramic material of the same kind is successfully prepared 2 O 3 Novel eutectic ceramic material LuAG.)

1. Large-size Al₂O₃The LuAG directional solidification eutectic ceramic is characterized in that the ceramic is a composite material containing an alumina phase and a lutetium aluminum garnet phase, and the chemical formula of the ceramic is Al₂O₃/Lu₃Al₅O₁₂The two-phase proportion of the alumina phase and the lutetium aluminum garnet phase is the eutectic composition point or the near eutectic composition point of the phase diagrams of the alumina phase and the lutetium aluminum garnet phase; al (Al)₂O₃the/LuAG directional solidification eutectic ceramic is prepared from irregularly arranged Al₂O₃And the LuAG is formed by mutual communication and coupling in space, and has a lamellar or cellular eutectic microstructure morphology.

2. Large-size Al according to claim 1₂O₃the/LuAG directional solidification eutectic ceramic is characterized in that Al is used without a crucible₂O₃Preparing a bar material with the maximum diameter of 15mm and the maximum length of 140mm by using LuAG eutectic ceramics; al (Al)₂O₃H of LuAG eutectic crystal ceramic bar_VThe hardness is 13-16 GPa, and the fracture toughness is 2-4 MPa.m^1/2。

3. Large-size Al as claimed in claim 1₂O₃The LuAG directional solidification eutectic ceramic light suspension zone-melting preparation method is characterized by comprising the following specific steps:

1) taking alumina powder and lutetium oxide powder as raw materials and Al₂O₃And Lu₂O₃The molar ratio of (82 +/-2) to (18 +/-2);

2) mixing alumina powder and lutetium oxide powder, mixing raw material powder and a ball milling solvent, and then sequentially performing ball milling, drying, cold pressing and sintering to obtain a prefabricated member;

3) directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al₂O₃LuAG directional solidification eutectic composite ceramic material; the solidification rate of the directional solidification is 10-50 mm/h, and the temperature gradient is 10³K/cm。

4. Large-size Al according to claim 3₂O₃/LuAG directional solidification eutectic ceramic light suspension zone melting preparation method is characterized in that in the step 2), the ball milling time is 2-24 hours, and the ball milling rotation speed is 100-600 r/min; the drying temperature is 50-80 ℃, and the drying time is 8-48 h.

5. Large-size Al according to claim 3₂O₃The LuAG directional solidification eutectic ceramic light suspension zone-melting preparation method is characterized in that in the step 2), the cold pressing process comprises two processes of mold dry pressing and cold isostatic pressing; wherein the pressure range of the mold dry pressing is 10-50 MPa, and the time of the mold dry pressing is 3-8 min; the pressure of the cold isostatic pressing is 160-300 MPa, and the time of the cold isostatic pressing is 20-30 min.

6. Large-size Al according to claim 3₂O₃The preparation method of the LuAG directional solidification eutectic ceramic optical suspension zone melting is characterized in that in the step 2), the sintering temperature is 1450-1550 ℃ and the time is 2-10 hours.

7. Large-size Al according to claim 3₂O₃The method for preparing the LuAG directional solidification eutectic ceramic light suspension zone melting is characterized in that in the step 3), when directional solidification is carried out, the prefabricated part is subjected to rotary preheating, and the rotation rate of the rotary preheating is 5-15 r/min.

8. Large-size Al according to claim 7₂O₃The LuAG directional solidification eutectic ceramic light suspension zone melting preparation method is characterized in that in the step 3), when a prefabricated part is partially melted to form a liquid drop, a seed crystal rod is lifted upwards to enable the lower end of the prefabricated part melted in the suspension zone to be connected with a seed crystal to form the suspension zone, after heat preservation is carried out for 1-2 min, a drawing system of a light suspension zone melting furnace is started to draw, directional solidification is carried out, a feed rod pushes the prefabricated part to continuously move towards the lower shaft direction until the whole prefabricated part is completely melted, the prefabricated part continuously moves towards the lower shaft direction, and after the prefabricated part is far away from a heat source area, the prefabricated part is solidified to obtain Al₂O₃LuAG eutectic ceramics.

9. Large-size Al according to claim 8₂O₃The preparation method of the LuAG directional solidification eutectic ceramic light suspension zone melting is characterized in that in the step 3), a heat source of the light suspension zone melting furnace is a xenon lamp, the power of the xenon lamp is 2-4 kW, the number of the xenon lamps is 2-4, and the xenon lamps are arranged in the light suspension zone melting furnace at equal intervals.

10. Large-size Al according to claim 3₂O₃The method for preparing the LuAG directional solidification eutectic ceramic through light suspension zone melting is characterized in that in the step 3), after directional solidification is finished, heating is stopped, and the obtained Al is subjected to light suspension zone melting₂O₃And putting the/LuAG eutectic ceramic in a quartz tube, cooling the quartz tube along with the furnace for 20-30 min to room temperature, and taking out the quartz tube.

Technical Field

The invention belongs to a preparation technology of directional solidification eutectic ceramics, and particularly relates to large-size Al₂O₃LuAG directional solidification eutectic ceramic and a light suspension zone-melting preparation method thereof.

Background

The directional solidification oxide eutectic composite material has the advantages of high melting point, low density, intrinsic high-temperature oxidation resistance and excellent high-temperature strength (the bending strength is kept stable when the high-temperature strength is close to the melting point), and particularly the high-temperature strength of the directional solidification oxide eutectic composite material is not reduced due to the expansion of sub-cracks. In addition, the unique eutectic structure also has excellent high temperature stability, and can keep the structure stable without coarsening when the temperature is close to the melting point. Therefore, the directionally solidified oxide eutectic composite material has attracted much attention and is considered as a new generation of ultra-high temperature structural material.

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 technique is urgently required. The optical suspension zone melting method is a new method capable of preparing large block oxide eutectic, can prepare 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 microstructure can be controlled to obtain the eutectic ceramic with excellent performance.

Al₂O₃The preparation of the/LuAG eutectic ceramic and the potential of the LuAG eutectic ceramic as a mechanical structural member are not researched yet. Wherein Lu has the smallest of rare earth elementsSo that Al is a relatively large amount of Al compared with other eutectic ceramics of the same type₂O₃The mechanical properties of the LuAG eutectic ceramic are possibly improved to some extent, and further a research basis is provided for the application of the LuAG eutectic ceramic to aeroengine structural parts.

Disclosure of Invention

The invention aims to provide large-size Al with excellent mechanical property₂O₃LuAG directional solidification eutectic ceramic and light suspension zone melting preparation method thereof, and prepared Al₂O₃the/LuAG eutectic ceramic has fine and controllable structure and excellent mechanical property, and the size can reach about 15mm of maximum diameter and about 140mm of maximum length.

In order to achieve the above object, the present invention provides the following technical solutions:

large-size Al₂O₃LuAG directionally solidified eutectic ceramic, which is a composite material containing an alumina phase and a lutetium aluminum garnet phase and has a chemical formula of Al₂O₃/Lu₃Al₅O₁₂The two-phase proportion of the alumina phase and the lutetium aluminum garnet phase is the eutectic composition point or the near eutectic composition point of the phase diagrams of the alumina phase and the lutetium aluminum garnet phase; al (Al)₂O₃the/LuAG directional solidification eutectic ceramic is prepared from irregularly arranged Al₂O₃And the LuAG is formed by mutual communication and coupling in space, and has a lamellar or cellular eutectic microstructure morphology.

The large-size Al₂O₃LuAG directionally solidified eutectic ceramic, Al without the use of a crucible₂O₃Preparing a bar material with the maximum diameter of 15mm and the maximum length of 140mm by using LuAG eutectic ceramics; al (Al)₂O₃H of LuAG eutectic crystal ceramic bar_VThe hardness is 13-16 GPa, and the fracture toughness is 2-4 MPa.m^1/2。

Large-size Al as claimed in claim 1₂O₃The preparation method of the LuAG directional solidification eutectic ceramic light suspension zone melting comprises the following specific steps:

1) taking alumina powder and lutetium oxide powder as raw materials and Al₂O₃And Lu₂O₃The molar ratio of (82 +/-2) to (18 +/-2);

2) mixing alumina powder and lutetium oxide powder, mixing raw material powder and a ball milling solvent, and then sequentially performing ball milling, drying, cold pressing and sintering to obtain a prefabricated member;

3) directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al₂O₃LuAG directional solidification eutectic composite ceramic material; the solidification rate of the directional solidification is 10-50 mm/h, and the temperature gradient is 10³K/cm。

The large-size Al₂O₃The preparation method of the LuAG directional solidification eutectic ceramic light suspension zone melting comprises the following steps of 2), ball milling time is 2-24 hours, and ball milling rotating speed is 100-600 r/min; the drying temperature is 50-80 ℃, and the drying time is 8-48 h.

The large-size Al₂O₃The LuAG directional solidification eutectic ceramic light suspension zone-melting preparation method, in step 2), the cold pressing process includes two processes of mould dry pressing and cold isostatic pressing; wherein the pressure range of the mold dry pressing is 10-50 MPa, and the time of the mold dry pressing is 3-8 min; the pressure of the cold isostatic pressing is 160-300 MPa, and the time of the cold isostatic pressing is 20-30 min.

The large-size Al₂O₃The preparation method of the LuAG directional solidification eutectic ceramic optical suspension zone melting comprises the step 2), wherein the sintering temperature is 1450-1550 ℃ and the time is 2-10 hours.

The large-size Al₂O₃The preparation method of the/LuAG directional solidification eutectic ceramic light suspension zone melting comprises the step 3), during directional solidification, performing rotary preheating on a prefabricated part, wherein the rotation rate of the rotary preheating is 5-15 r/min.

The large-size Al₂O₃A LuAG directional solidification eutectic ceramic light suspension zone melting preparation method, in the step 3), when the prefabricated part is partially melted to form a liquid drop, the seed crystal rod is lifted upwards to enable the lower end of the prefabricated part melted in the suspension zone to be connected with the seed crystal to form the suspension zone, after heat preservation is carried out for 1-2 min, a drawing system of a furnace in the light suspension zone is started to draw, directional solidification is carried out, the feeding rod pushes the prefabricated part to continuously move towards the lower shaft direction until the whole prefabricated part is completely melted, and the prefabricated part continuously moves towards the lower shaft directionAfter moving and keeping away from the heat source area, the prefabricated part is solidified to obtain Al₂O₃LuAG eutectic ceramics.

The large-size Al₂O₃The preparation method of the LuAG directional solidification eutectic ceramic light suspension zone melting comprises the step 3), wherein a xenon lamp is used as a heat source of a light suspension zone melting furnace, the power of the xenon lamp is 2-4 kW, the number of the xenon lamps is 2-4, and the xenon lamps are arranged in the light suspension zone melting furnace at equal intervals.

The large-size Al₂O₃The preparation method of the LuAG directional solidification eutectic ceramic light suspension zone melting comprises the following steps of 3), stopping heating after directional solidification is finished, and obtaining Al₂O₃And putting the/LuAG eutectic ceramic in a quartz tube, cooling the quartz tube along with the furnace for 20-30 min to room temperature, and taking out the quartz tube.

The design idea of the invention is as follows:

among rare earth elements, lutetium element has the smallest ionic radius and lower oxygen vacancy forming energy, and a compound ceramic material containing Lu element generally has outstanding high-temperature mechanical properties. However, there have been reports of public disclosure that it is difficult to obtain Al with large size and high quality due to the imperfect preparation technology or the unreasonable preparation process₂O₃LuAG eutectic ceramics. Accordingly, the key mechanical properties of the material have not been reported. Based on the supposition that the alumina-based eutectic ceramic containing Lu element is also highly possible to be a new material with excellent mechanical property, particularly high-temperature mechanical property, the invention aims at Al₂O₃The directional solidification technology of the LuAG eutectic ceramic is researched, and the large-size high-quality Al is successfully prepared₂O₃The LuAG eutectic ceramic is characterized in key mechanical properties, and provides preparation technical support and performance data accumulation for application as an aeroengine structural member.

The invention has the advantages and beneficial effects that:

the invention successfully utilizes the light suspension zone melting technology to obtain the novel large-size Al with high hardness and high fracture toughness under the condition of not using a crucible₂O₃LuAG directionally solidified eutectic ceramic material having a shape with a maximum diameter of about 15mm, and a maximum length of about 140 mm. The present inventors have found that Al₂O₃The microstructure of the/LuAG eutectic ceramic is closely related to the solidification rate, and as the solidification rate increases, the eutectic structure in the material gradually evolves from a lamellar structure to a cellular structure. And the larger the solidification rate, the smaller the average eutectic lamella spacing. Therefore, by accurately controlling the solidification rate (10-50 mm/h), the Al with key mechanical properties such as hardness, fracture toughness and the like superior to those of the known eutectic ceramic material of the same type is successfully prepared₂O₃Novel eutectic ceramic material LuAG.

Drawings

FIG. 1 shows Al₂O₃-Lu₂O₃A phase diagram; in the figure, the abscissa Mobile fraction Al₂O₃Represents Al₂O₃The ordinate Temperature represents the Temperature (. degree. C.).

FIG. 2 is a schematic view of a light suspension zone furnace used in the present invention; in the figure, 1 quartz tube, 2 elliptical mirror, 3 xenon lamp, 4 seed rod, 5 lower shaft, 6 melting zone, 7 feeding rod, 8 upper shaft and 9 quartz tube inner cavity.

FIG. 3 shows Al prepared in examples 1 to 8₂O₃The macro topography of the/LuAG directional solidification eutectic ceramic sample rod has solidification rates of 50mm/h, 30mm/h, 20mm/h and 10mm/h respectively.

FIG. 4 shows Al prepared in examples 1 to 8₂O₃A cross section appearance diagram of a eutectic structure of a LuAG directional solidification eutectic ceramic sample rod; wherein, (a) the solidification rate is 10mm/h, (b) the solidification rate is 30mm/h, and (c) the solidification rate is 50 mm/h.

FIG. 5 shows Al prepared in examples 1 to 8₂O₃A longitudinal section morphology diagram of a eutectic structure of a LuAG directional solidification eutectic ceramic sample rod; wherein, (a) the solidification rate is 10mm/h, and (b) the solidification rate is 30 mm/h.

FIG. 6 shows Al prepared in example 4₂O₃XRD pattern of LuAG directional solidification eutectic ceramic sample rod; wherein (a) the solidification rate is 10mm/h, the abscissa 2 θ represents the diffraction angle (°), and the ordinate Intensity represents the relative Intensity (a.u.); (b) the solidification rate was 30mm/h, the abscissa 2. theta. represents the diffraction angle (. degree.), and the ordinate Intensity represents the relativeIntensity (a.u.).

FIG. 7 shows Al prepared in example 4₂O₃3D space structure morphology diagram (a) of LuAG directional solidification eutectic ceramic sample rod, three-dimensional structure (b) of LuAG and Al₂O₃The three-dimensional structure (c) of (1).

Detailed Description

In the specific implementation process, the invention provides large-size Al₂O₃The LuAG directional solidification eutectic ceramic and the optical suspension zone-melting preparation method thereof comprise the following steps:

taking alumina powder and lutetium oxide powder as raw materials and Al₂O₃And Lu₂O₃The molar ratio of (82 +/-2) to (18 +/-2);

mixing alumina powder and lutetium oxide powder, mixing raw material powder and a ball milling solvent, and then sequentially performing ball milling, drying, cold pressing and sintering to obtain a prefabricated member;

directionally solidifying the prefabricated member in a light suspension zone melting furnace to obtain Al₂O₃LuAG authigenic eutectic composite ceramic material;

the solidification rate of the directional solidification is 10-50 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.

In the present invention, the mixed raw material powder is Al₂O₃And Lu₂O₃The mixture of (1), the Al₂O₃The purity of (b) is preferably 99.9 wt%; the Lu₂O₃The purity of (C) is preferably 99.99 wt%. In the present invention, the Al₂O₃And Lu₂O₃The particle size of (a) is preferably in the micron order; the invention aims at the micron-sized Al₂O₃And micron-sized Lu₂O₃The 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 Lu₂O₃In the mixture of (1), Al₂O₃And Lu₂O₃The molar ratio of (82 +/-2) to (18 +/-2); as shown in FIG. 1, the present invention is preferably based on Al₂O₃And Lu₂O₃Phase diagram of (1), determination of Al₂O₃And Lu₂O₃The eutectic reaction 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 2-24 h, and more preferably 7-8 h; the rotating speed of the ball milling is preferably 100-600 r/min.

After the ball milling is finished, drying the obtained ball milling material, wherein the drying time is preferably 8-48 h; the drying temperature is preferably 50-80 ℃, and more preferably 70-80 ℃. 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 completed, the present invention preferably presses the obtained dry powder to obtain a long strip sample. In the present invention, the pressing preferably includes two processes of mold dry pressing and cold isostatic pressing which are performed in sequence; the pressure of the dry pressing of the die is preferably 10-50 MPa, more preferably 25-28 MPa, and the time is preferably 3-8 min, more preferably 5 min; the pressure of the cold isostatic pressing is preferably 160-300 MPa, more preferably 240-260 MPa, and the time is preferably 20-30 min, more preferably 30 min. The equipment for dry pressing and cold isostatic pressing of the die 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. The invention obtains the strip-shaped sample by pressing, and is convenient for subsequent sintering.

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 10 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. 36% (mass fraction) of Al in the sintering process₂O₃And Lu₂O₃React to form Lu₃Al₅O₁₂(LuAG), remainder Al₂O₃Formation of Al with LuAG₂O₃A LuAG 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 Al₂O₃LuAG eutectic ceramics. 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 3-4, 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 10-50 mm/h by controlling the heat source of the optical suspension zone melting furnace under the above conditions.

After the directional solidification is finished, the heating is preferably stopped, the obtained material is placed in a quartz tube, and is cooled along with a furnace for 20-30 min to room temperature and then taken out, so that the thermal stress cracks on the surface of the material can be prevented.

The invention provides large-size Al prepared by the preparation method in the technical scheme₂O₃LuAG eutectic ceramics.

In the present invention, the Al₂O₃the/LuAG directional solidification eutectic ceramic is prepared from irregularly arranged Al₂O₃And the LuAG is formed by mutual communication and coupling in space, and has a lamellar or cellular eutectic microstructure morphology. The Al is₂O₃H of LuAG eutectic crystal ceramic_VThe hardness is 13-16 GPa, and the fracture toughness is 2-4 MPa.m^1/2. The Al is₂O₃the/LuAG eutectic ceramic size can reach the maximum diameter of about 15mm and the maximum length of about 140 mm.

In the following embodiments, specifically, directional solidification is performed in the optical suspension zone furnace shown in fig. 2, a quartz tube 1 is vertically disposed in the optical suspension zone furnace, an upper shaft 8 is disposed at an upper portion of an inner cavity 9 of the quartz tube, a lower shaft 5 is disposed at a lower portion of the inner cavity 9 of the quartz tube, a feed rod 7 (i.e., a preform) is mounted at a lower end of the upper shaft 8, a seed rod 4 is mounted at an upper end of the lower shaft 5, the upper shaft 8, the feed rod 7, the seed rod 4, and the lower shaft 5 are located on the same vertical axis, and a melting zone 6 is formed between the feed rod 7 and the seed rod 4 which are oppositely disposed. The outer side of the quartz tube 1 is provided with an elliptical mirror 2 and a hernia lamp 3, the light spot of the hernia lamp 3 corresponds to the melting zone 6, and the elliptical mirror 2 corresponds to the hernia lamp 3 and is used for adjusting the light path of the hernia lamp 3.

Before directional solidification, the preform (i.e. feed rod 7) is suspended from the upper shaft 8 with nickel wire, and Al is added₂O₃The seed rod 4 is fixed on the lower shaft 5 to ensure the prefabricated part and Al₂O₃The axis of the seed rod 4 is located on a straight line, then a heating power supply is started, the temperature is automatically raised, the elliptical mirror 2 is adjusted to change the light path, the light spot of the xenon lamp 3 is ensured to be concentrated at the tip of the prefabricated part, and then the preheating and directional solidification processes of the prefabricated part are carried out.

The present invention will be described in further detail below with reference to examples.

Example 1

In this example, Al is added₂O₃And Lu₂O₃Mixture of (molar ratio of Al)₂O₃:Lu₂O₃82:18) was added to analytically pure ethanol and placed in a planetary ball mill for 6h (ball milling speed 400r/min) and the resulting mixture was dried in a drying cabinet at 60 ℃ for 12 h.

Pressing the dried powder under 25MPa for 5min, and dry-pressing a sample with the size of 10mm multiplied by 100mm by a mould; then carrying out cold isostatic pressing under the pressure of 280MPa, and carrying for 30min to obtain a strip sample; then sintering the obtained strip sample in a sintering furnace for 10 hours 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 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, keeping the temperature for 1min, starting a drawing system (namely an upper shaft, a lower shaft and a feed rod) of the light suspension zone melting furnace to draw, carrying out directional solidification, and setting the temperature gradient to be 10 according to the drawing speed (namely the solidification speed) of 10mm/h³K/cm, the feeding rod pushes the prefabricated part to continuously move towards the lower shaft direction until the whole prefabricated part is completely melted, the prefabricated part continuously moves towards the lower shaft direction, and after the prefabricated part is far away from a heat source area formed by the xenon lamp, the prefabricated part is solidified to obtain Al₂O₃LuAG eutectic ceramic, with a diameter of about 13 mm.

Example 2

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 Al₂O₃LuAG eutectic ceramics.

Example 3

This example differs from example 1 in that: at a withdrawal rate of 30mm/h (i.e.the solidification rate), a temperature gradient of 10 is set³K/cm, directional solidification is carried out to obtain Al₂O₃LuAG eutectic ceramics.

Example 4

This example differs from example 1 in that: at a withdrawal rate of 50mm/h (i.e.the solidification rate), a temperature gradient of 10 is set³K/cm, directional solidification is carried out to obtain Al₂O₃LuAG eutectic ceramics.

Performance testing

For Al prepared in examples 1 to 4₂O₃The tissue structure of the LuAG eutectic ceramic sample rod is characterized, the mechanical property is tested, and the test method and the result are as follows.

1) And (3) observing macro morphology: al prepared in examples 1 to 4₂O₃The result of observing the macroscopic morphology of the LuAG eutectic ceramic sample rod is shown in figure 3.

2) And (3) observing the tissue morphology: al prepared in examples 1 to 4 was cut out by a diamond dicing saw₂O₃The cross section and the longitudinal section results of the/LuAG eutectic ceramic sample rod are shown in fig. 4 and fig. 5 respectively after SEM test.

FIG. 4 shows Al prepared at different solidification rates for examples 1, 3 and 4₂O₃The cross section morphology of the eutectic structure of the LuAG eutectic ceramic sample rod can be seen from figure 4, the distribution of eutectic lamina presents a cellular structure distribution, and the lamella spacing becomes smaller along with the increase of the solidification rate.

FIG. 5 shows Al prepared at different solidification rates for examples 1 and 3₂O₃The longitudinal section morphology of the eutectic structure of the LuAG eutectic ceramic sample rod can be seen from figure 5, the longitudinal section of the lamellar structure is longitudinally distributed in a banded structure, and a three-dimensional interlocking structure between two phases in the eutectic ceramic is embodied.

3) Phase composition analysis: al prepared in examples 1 and 3 was cut out by a diamond dicing saw₂O₃The results of XRD tests carried out on a LuAG eutectic ceramic test bar are shown in FIG. 6. As can be seen from FIG. 6, the eutectic ceramic sample rod contains only Al₂O₃And LuAG two phases.

4) And (3) observing three-dimensional morphology features: a sample rod was cut out by a diamond dicing cutter, and Al prepared in example 1 was subjected to X-ray three-dimensional imaging (XCT)₂O₃The three-dimensional structure of the/LuAG eutectic ceramic sample rod was observed, and the results are shown in FIG. 7. Wherein (a) is Al prepared in example 1₂O₃A 3D space structure morphology chart of the LuAG eutectic ceramic sample rod, (b) is a three-dimensional structure of LuAG,(c) is Al₂O₃The three-dimensional structure of (1). As can be seen from (a) to (c) in FIG. 7, Al produced by the present invention₂O₃the/LuAG eutectic ceramic has a spatial three-dimensional continuous interlocking structure.

5) Microhardness and fracture toughness testing: the sample rods were cut with a diamond scribe-saw and the micro-indentation technique was used to apply to the Al prepared in examples 1 and 2₂O₃The room temperature hardness and the fracture toughness of the LuAG eutectic ceramic test bar are measured, the experimental load is 30N, and the holding time is 15 s. The results show that the room temperature hardness of example 1 is H_VThe room temperature hardness of example 3 is H, 14.2 ± 0.2GPa_V15.1 +/-0.3 GPa. Compared with other eutectic ceramic systems in the prior art, Al₂O₃LuAG has higher Vickers hardness, and shows the application potential of LuAG as a structural member.

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 material_ICThe expression is as follows:

K_IC＝0.016·(E/H_v)^0.5·(P/c^1.5) (ii) a Formula (1)

In the formula (1), E is an elastic modulus (GPa), H_VVickers hardness (GPa), P load (N) and c crack half-length (μm). The fracture toughness K of examples 1 and 3 was calculated according to the formula (1)_ICRespectively is 2.8 +/-0.3 MPa.m^1/2And 3.3. + -. 0.3 MPa. m^1/2。

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above, and therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention shall fall within the protection scope of the present invention.