Preparation method of beryllium-aluminum alloy surface composite reinforced modified layer
阅读说明：本技术 一种铍铝合金表面复合强化改性层的制备方法 (Preparation method of beryllium-aluminum alloy surface composite reinforced modified layer ) 是由 杨勋刚 余良波 李鱼飞 姚志勇 纪和菲 陈冬 于 2021-05-26 设计创作，主要内容包括：本发明公开了一种铍铝合金表面氧化铍/氧化铝双相颗粒复合强化改性层的制备方法。采用在铍铝合金表面预烧微米金属铝粉、纳米氧化铝粉与纳米氧化铍粉三元预混复合粉体的方式,结合电子束重熔与后续热处理获得了高硬度与强化相颗粒梯度式分布的合金表面改性层。采用上述技术路线可避免使用金属铍粉造成的不利影响与表面改行层的开裂失效,实现了改性层与合金基体之间的冶金结合,保证了表面改性层的结构稳定性。该方法工艺路线简便可行,可有效解决铸造铍铝合金用作电子包封材料时对表面涂层热物性能的要求,具有良好的实际工程应用前景。(The invention discloses a preparation method of a beryllium oxide/aluminum oxide dual-phase particle composite strengthening modified layer on the surface of a beryllium-aluminum alloy. An alloy surface modification layer with high hardness and reinforcing phase particle gradient distribution is obtained by adopting a mode of pre-sintering micron metal aluminum powder, nano aluminum oxide powder and nano beryllium oxide powder ternary pre-mixed composite powder on the surface of the beryllium aluminum alloy and combining electron beam remelting and subsequent heat treatment. By adopting the technical route, adverse effects caused by using the beryllium metal powder and cracking failure of the surface modified layer can be avoided, metallurgical bonding between the modified layer and the alloy matrix is realized, and the structural stability of the surface modified layer is ensured. The method has simple and feasible process route, can effectively meet the requirement on the thermal property of the surface coating when the cast beryllium-aluminum alloy is used as the electronic packaging material, and has good practical engineering application prospect.)
1. A preparation method of a beryllium-aluminum alloy surface composite reinforced modified layer is characterized by comprising the following steps:
s1, preparing premixed composite powder: carrying out dry ball milling and mixing on micron metal aluminum powder, nano alumina powder and nano beryllium oxide powder in a certain weight ratio in high-purity argon or helium to obtain uniformly mixed premixed composite powder;
s2, beryllium-aluminum alloy surface pretreatment: grinding and polishing the surface of the beryllium-aluminum alloy, ultrasonically cleaning the surface of the beryllium-aluminum alloy by using absolute ethyl alcohol and deionized water in sequence, and then air-drying the surface of the beryllium-aluminum alloy for later use to obtain a beryllium-aluminum alloy substrate;
s3, sintering preforming: in high-purity argon or helium, spreading the pre-mixed composite powder with a certain thickness on a beryllium-aluminum alloy substrate in the step S1, and then transferring the pre-mixed composite powder into a vacuum sintering furnace for sintering, so that the pre-mixed composite powder is primarily cured and formed on the beryllium-aluminum alloy substrate to obtain a sintered and preformed beryllium-aluminum alloy/pre-mixed powder compound;
s4, electron beam cladding: under the vacuum condition, firstly preheating the beryllium-aluminum alloy/premixed powder compound in the step S3, carrying out electron beam surface remelting after keeping the temperature for a period of time, controlling parameters such as the diameter, power and scanning speed of an electron beam spot to complete remelting of the upper surface of the alloy, and then introducing high-purity argon or helium to assist in cooling to room temperature;
s5, heat treatment: and (5) carrying out vacuum heat treatment on the beryllium-aluminum alloy substrate subjected to electron beam cladding in the step S4 to eliminate residual thermal stress, and cooling the beryllium-aluminum alloy substrate to room temperature after the residual thermal stress is eliminated.
2. The preparation method of the beryllium-aluminum alloy surface composite strengthening modified layer according to claim 1, characterized by comprising the following steps: in the step S1, the average particle size of the micron metal aluminum powder is 30-150 microns, and the average particle size of the nano aluminum oxide powder and the average particle size of the nano beryllium oxide are both 20-200 nanometers.
3. The preparation method of the beryllium-aluminum alloy surface composite strengthening modified layer according to claim 1, characterized by comprising the following steps: in the step S1, the aluminum powder is composed of, by weight, 20-30% of nano aluminum oxide powder, 15-30% of nano beryllium oxide powder, and the balance of micro metal aluminum powder.
4. The preparation method of the beryllium-aluminum alloy surface composite strengthening and modifying layer according to claim 1 or 3, which is characterized by comprising the following steps: in the step S1, the weight ratio of the nano alumina powder to the nano beryllium oxide powder should not be lower than 1.2.
5. The preparation method of the beryllium-aluminum alloy surface composite strengthening modified layer according to claim 1, characterized by comprising the following steps: in the step S1, the ball milling time is 2-5 hours, the weight ratio of the ball to the composite mixed powder is controlled to be 1: 0.8-1.2, and after the end, the premixed composite powder is taken out in a high-purity argon or helium environment and stands for later use.
6. The preparation method of the beryllium-aluminum alloy surface composite strengthening modified layer according to claim 1, characterized by comprising the following steps: in the step S3, the powder spreading thickness of the premixed composite powder on the beryllium-aluminum alloy substrate is 0.6 to 1.5 mm.
7. The preparation method of the beryllium-aluminum alloy surface composite strengthening and modifying layer according to claim 1 or 6, which is characterized by comprising the following steps: in step S3, the vacuum degree in the sintering furnace is not higher than 510-2Pa, the sintering temperature is 420-600 ℃, and the heat preservation time is 10-25 minutes.
8. The preparation method of the beryllium-aluminum alloy surface composite strengthening modified layer according to claim 1, characterized by comprising the following steps: in step S4, the vacuum degree in the electron beam furnace is not higher than 5 × 10-2Pa, preheating the beryllium-aluminum alloy/premixed powder composite sintered and preformed in the step S3 at 450-560 ℃, and keeping the temperature for 5-10 minutes.
9. The preparation method of the beryllium-aluminum alloy surface composite strengthening and modifying layer according to claim 1 or 8, which is characterized by comprising the following steps: in the step S4, the power of the electron beam is 1.2 to 2.5kW, the diameter of a light spot is 5 to 10mm, the linear scanning speed is 8 to 15mm/S, the remelting of the upper surface of the alloy is completed in a reciprocating Y-shaped path, and finally, an electron beam cladding layer with the thickness not less than 400 microns is formed on the surface of the beryllium-aluminum alloy.
10. The preparation method of the beryllium-aluminum alloy surface composite strengthening modified layer according to claim 1, characterized by comprising the following steps: in step S5, the vacuum heat treatment conditions are: vacuum degree in furnace is not higher than 5X 10-2Pa; in the first stage, the heating rate is 10-15 ℃/min, the heat preservation temperature is 480-520 ℃, and the heat preservation time is 5-8 hours; and in the second stage, reducing the heating power of the furnace body to 0, cooling the furnace to 280-320 ℃, improving the heating power of the furnace body and preserving the heat for 2-3 hours.
Technical Field
The invention relates to the field of surface modification of non-ferrous metal materials, in particular to surface modification and coating preparation of beryllium-aluminum alloy, and particularly relates to a preparation method of a beryllium-aluminum alloy surface composite reinforced modified layer.
Background
High thermal conductivity and the ability to match the Coefficient of Thermal Expansion (CTE) of the base material are the primary performance requirements for electronic component integrated packaging materials. In addition, increasingly developed electronic technologies and industries place increasingly higher demands on the density, strength, dimensional stability, damping properties, and even surface state (coatings, etc.) of the encapsulating material. Of the many candidate materials that satisfy the conditions, beryllium, copper, tungsten, aluminum metal matrix composites have their own unique advantages, with beryllium-beryllium oxide (E material) and beryllium aluminum alloy systems showing considerable competitive advantages due to their high damping, thermal and specific stiffness properties. The metallic beryllium-based composite material reinforced by beryllium oxide (BeO) particles generally has high thermal conductivity not lower than 240W/m.k, CTE value not higher than 6.1ppm/K and good dimensional stability in a wide temperature range, is one of more ideal electronic packaging materials, but the preparation process and the cost limit the wide application of the metallic beryllium-based composite material, and is mainly shown in the following steps: the method needs to prepare spherical beryllium powder, uniformly mix the beryllium powder with particles of the scale oxide powder in a similar powder metallurgy mode, perform cold hot isostatic pressing and the like, and needs to be matched with complex equipment and procedures for reducing the toxicity and high anti-oxidation requirements of the beryllium powder.
Beryllium-aluminum alloy materials have thermal conductivities, CTE values (210W/m.k, 8.7ppm/K) and dimensional stabilities similar to those of the E materials. The cast beryllium-aluminum alloy has higher damping performance and machining performance than powder metallurgy alloy and greatly reduces the preparation cost. The beryllium-aluminum alloy is a two-phase metal matrix composite material consisting of metal beryllium and aluminum, and in practical engineering application, on the premise of overcoming the defects of beryllium columnar dendrite and solidification in casting the beryllium-aluminum alloy, the technical problem of the surface coating or plating layer of the beryllium-aluminum alloy needs to be further solved. Because the electrochemical properties of beryllium and aluminum are greatly different and the standard electrochemical potential is lower, the oxidation film forming capability of two phases is greatly different in the conventional surface modification treatment processes of anodic oxidation, micro-arc oxidation and the like, and the process is not mature. Furthermore, surface coatings tend to suffer from low hardness/strength, mismatch with substrate CTE parameters, and the like.
Disclosure of Invention
The surface strengthening layer with high hardness, good thermal conductivity and thermal stability and high bonding strength with the matrix can be obtained by means of metallurgical bonding and composite strengthening phase increasing, and the realization means comprises laser, electron beam, electric arc or plasma surface cladding. By reasonably selecting the strengthening phase material and combining the above modes, a remelted layer with the thickness of several micrometers to hundreds of micrometers can be prepared on the surface of the cast beryllium-aluminum alloy, and the beryllium-aluminum alloy shows unique microstructure and thermophysical properties, so that the beryllium-aluminum alloy is used as an electronic packaging material in an auxiliary manner. Due to excellent tissue and performance compatibility with a beryllium-aluminum alloy matrix, the beryllium oxide and the aluminum oxide particles can be used as an ideal particle strengthening phase of the beryllium-aluminum alloy. According to the knowledge of the applicant, at present, the related literature reports on the realization of beryllium oxide/aluminum oxide composite strengthening of the beryllium-aluminum alloy surface through surface cladding treatment at home and abroad are few, and related research and application fields are still blank.
The invention aims to: the invention provides a preparation method of a beryllium-aluminum alloy surface composite strengthening modified layer, which solves part of problems or defects faced by the existing method for casting a beryllium-aluminum alloy for an electronic component packaging material. On the basis of retaining the characteristics of good thermophysical property, damping property, dimensional stability, low density and the like of the cast beryllium-aluminum alloy, the surface state of the alloy is further modified, the total surface microstructure is improved, the surface hardness of the alloy is improved, and adverse factors brought by surface chemical plating are avoided.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a beryllium-aluminum alloy surface composite reinforced modified layer is characterized by comprising the following steps:
s1, preparing premixed composite powder: carrying out dry ball milling and mixing on micron metal aluminum powder, nano alumina powder and nano beryllium oxide powder in a certain weight ratio in high-purity argon or helium to obtain uniformly mixed premixed composite powder;
s2, beryllium-aluminum alloy surface pretreatment: grinding and polishing the surface of the beryllium-aluminum alloy, ultrasonically cleaning the surface of the beryllium-aluminum alloy by using absolute ethyl alcohol and deionized water in sequence, and then air-drying the surface of the beryllium-aluminum alloy for later use to obtain a beryllium-aluminum alloy substrate;
s3, sintering preforming: in high-purity argon or helium, spreading the pre-mixed composite powder with a certain thickness on a beryllium-aluminum alloy substrate in the step S1, and then transferring the pre-mixed composite powder into a vacuum sintering furnace for sintering, so that the pre-mixed composite powder is primarily cured and formed on the beryllium-aluminum alloy substrate to obtain a sintered and preformed beryllium-aluminum alloy/pre-mixed powder compound;
s4, electron beam cladding: under the vacuum condition, firstly preheating the beryllium-aluminum alloy/premixed powder compound in the step S3, carrying out electron beam surface remelting after keeping the temperature for a period of time, controlling parameters such as the diameter, power and scanning speed of an electron beam spot to complete remelting of the upper surface of the alloy, and then introducing high-purity argon or helium to assist in cooling to room temperature;
s5, heat treatment: and (5) carrying out vacuum heat treatment on the beryllium-aluminum alloy substrate subjected to electron beam cladding in the step S4 to eliminate residual thermal stress, and cooling the beryllium-aluminum alloy substrate to room temperature after the residual thermal stress is eliminated.
Further, in the step S1, the average particle size of the micron metal aluminum powder is 30 to 150 microns, and the average particle size of the nano aluminum oxide powder and the average particle size of the nano beryllium oxide are both 20 to 200 nanometers.
Further, in the step S1, the aluminum oxide powder is 20 to 30% by weight, the beryllium oxide powder is 15 to 30% by weight, and the balance is the micron metal aluminum powder.
Further, in the step S1, the weight ratio of the nano alumina powder to the nano beryllium oxide powder should be not less than 1.2.
Further, in the step S1, the beads used in the ball milling process are made of corundum or agate.
Further, in the step S1, the ball milling time is 2-5 hours, the weight ratio of the ball to the composite mixed powder is controlled to be 1: 0.8-1.2, and after the end, the premixed composite powder is taken out in a high-purity argon or helium environment and is kept stand for later use.
Further, in the step S2, the purity of the absolute ethyl alcohol used is analytical grade.
Further, in the step S3, the powder spreading thickness of the premixed composite powder on the beryllium-aluminum alloy substrate is 0.6 to 1.5 mm.
Further, in the step S3, the vacuum degree in the sintering furnace is not higher than 5 × 10-2Pa (when the vacuum degree is marked, the smaller the numerical value of the absolute number is, the better the internal vacuum condition is, the sintering temperature is 420 to 600 ℃, and the heat preservation time is 10 to 25 minutes.
Further, in the step S4, the vacuum degree in the electron beam furnace is not higher than 5 × 10-2Pa, preheating the beryllium-aluminum alloy/premixed powder composite sintered and preformed in the step S3 at 450-560 ℃, and keeping the temperature for 5-10 minutes.
Further, in the step S4, the power of the electron beam is 1.2 to 2.5kW, the diameter of the light spot is 5 to 10mm, the linear scanning speed is 8 to 15mm/S, the remelting of the upper surface of the alloy is completed in a reciprocating zigzag path, and finally an electron beam cladding layer with a thickness of not less than 400 microns is formed on the surface of the beryllium-aluminum alloy.
Further, in the step S4, the gas flow of the high-purity argon or helium is 15-30L/min;
further, in step S5, the vacuum heat treatment conditions are: vacuum degree in furnace is not higher than 5X 10-2Pa。
Further, in the step S5, in the first stage, the temperature rising rate is 10-15 ℃/min, the heat preservation temperature is 480-520 ℃, and the heat preservation time is 5-8 hours; and in the second stage, reducing the heating power of the furnace body to 0, cooling the furnace to 280-320 ℃, improving the heating power of the furnace body and preserving the heat for 2-3 hours.
The invention has the beneficial effects that:
(1) the invention provides a preparation method of a beryllium oxide/aluminum oxide dual-phase particle composite reinforced modified layer on the surface of a beryllium aluminum alloy based on electron beam treatment, which can effectively meet the requirements of the thermal property of a surface coating when the cast beryllium aluminum alloy is used as an electronic packaging material, wherein the requirements comprise surface hardness, the matching property of the coating and a base material on thermal conductivity and thermal expansion coefficient parameters, surface modification adaptability (such as physical and chemical coating and insulating paint addition) which can be faced when the beryllium aluminum alloy is used for high-density integrated packaging in the future and the like.
(2) The aluminum powder, the aluminum oxide and the beryllium oxide powder are compounded in a ternary mode, so that the safety protection problem and high cost caused by using the metal beryllium powder are avoided, and the components of the aluminum oxide are higher than those of the beryllium oxide, so that the consumption of the beryllium oxide is reduced on the basis of keeping the strengthening effect of the oxide nanoparticles on the alloy, and the aluminum oxide-beryllium powder alloy has good economic significance. Finally, the addition of the metal aluminum powder is beneficial to uniformly wrapping oxides into a melt due to the surface tension and particle agglomeration in the instant melting process of the pre-sintered powder, and after the oxide particles are mixed with a liquid phase in a beryllium-aluminum alloy melting area, the oxide particles are distributed on the surface of the matrix in a gradient manner, so that the structure between the matrix and a matrix heat affected area and a remelting area cannot be mutated, and the structural stability of a surface remelting layer is ensured.
(3) The pre-sintering of the premixed composite powder can ensure the stable existence of the powder on the alloy surface under the impact action of vacuum and electron beams, and the adoption of the electron beams instead of laser as a heating source has obvious advantages in equipment threshold, technical difficulty and heating power. The homogenization near the bonding layer is realized to a certain extent by the heat preservation of the high-temperature section in the subsequent heat treatment, the thermal stress of the remelted layer on the surface of the alloy can be further released by the low-temperature section, and the generation of defects in the surface modified layer is avoided.
The beryllium-aluminum alloy surface modification layer reinforced by the aluminum oxide/beryllium oxide particles is beneficial to the combination of materials and the electronic board base material, simultaneously improves the alloy surface hardness, and realizes effective metallurgical combination between the modification layer and the alloy base body after electron beam cladding. In conclusion, the method has good practical engineering application prospect.
The main scheme and the further selection schemes can be freely combined to form a plurality of schemes which are all adopted and claimed by the invention; in the invention, the selection (each non-conflict selection) and other selections can be freely combined. The skilled person in the art can understand that there are many combinations, which are all the technical solutions to be protected by the present invention, according to the prior art and the common general knowledge after understanding the scheme of the present invention, and the technical solutions are not exhaustive herein.
Drawings
FIG. 1 is a metallographic microscopic image of a modified layer of the beryllium-aluminum alloy surface composite strengthening in example 1.
FIG. 2 is a metallographic microscopic image of a modified layer of the beryllium-aluminum alloy surface composite strengthening in example 3.
FIG. 3 is a Scanning Electron Microscope (SEM) image of a beryllium-aluminum alloy surface modification layer in comparative example 1.
Fig. 4 is a Scanning Electron Microscope (SEM) image of the beryllium-aluminum alloy surface modification layer in comparative example 2.
Detailed Description
The following non-limiting examples serve to illustrate the invention.
Example 1:
a preparation method of a beryllium-aluminum alloy surface composite reinforced modified layer comprises the following steps:
(1) preparing metal aluminum powder with the average particle size of about 100 micrometers, alumina powder with the average particle size of about 100 nanometers and beryllium oxide powder according to the weight parts of 20 percent of alumina powder, 15 percent of nano beryllium oxide powder and the balance of metal aluminum powder, carrying out dry ball milling and mixing powder in high-purity argon, controlling the weight ratio of ball beads to composite mixed powder to be 1: 1, carrying out ball milling for 2 hours, taking out premixed powder in the high-purity argon and standing for later use;
(2) grinding and polishing the surface of the beryllium-aluminum alloy to be treated, ultrasonically cleaning the surface of the beryllium-aluminum alloy by using analytically pure absolute ethyl alcohol and deionized water in sequence, and air-drying the surface of the beryllium-aluminum alloy for later use to obtain a beryllium-aluminum alloy substrate;
(3) in high-purity argon, pre-mixed composite powder with the thickness of about 0.6 mm is flatly paved on a beryllium-aluminum alloy substrate, and then the substrate is transferred into a vacuum sintering furnace. At a vacuum degree of 3X 10-2Under the condition of Pa, preserving heat for 25 minutes at the temperature of 420 ℃ and completing sintering to obtain a sintered preformed beryllium-aluminum alloy/premixed powder compound;
(4) transferring the beryllium-aluminum alloy/premixed powder composite into an electron beam furnace at a temperature of 3.0 multiplied by 10-2Preheating the beryllium-aluminum alloy/premixed powder composite in the previous step to 450 ℃ under the Pa vacuum degree, preserving heat for 10 minutes, and starting the power supply after the heat preservation is finishedRemelting the surface of an electron beam by a source, controlling the power of the electron beam to be 1.2kW, the diameter of a light spot to be 5mm, and the linear scanning speed to be 8mm/s, completing remelting of the upper surface of the alloy by a reciprocating zigzag path, and introducing high-purity argon at a gas flow of 15L/min to assist cooling to room temperature;
(5) transferring the beryllium-aluminum alloy substrate subjected to electron beam cladding to a vacuum heat treatment furnace, and vacuumizing to 5 multiplied by 10- 2And Pa, firstly heating to 480 ℃ at the speed of 10 ℃/min and preserving heat for 5 hours, then closing the power supply and cooling the furnace to 280 ℃, then re-feeding electricity and preserving heat for 2 hours, and cooling the furnace to room temperature after finishing.
Example 2:
a preparation method of a beryllium-aluminum alloy surface composite reinforced modified layer comprises the following steps:
(1) preparing metal aluminum powder with average particle size of about 150 micrometers, alumina powder with average particle size of about 200 nanometers and beryllium oxide powder according to the weight parts of the alumina powder, the nano beryllium oxide powder and the balance of the metal aluminum powder, carrying out dry ball milling and mixing in high-purity argon, wherein ball beads used for ball milling are corundum, the weight ratio of the ball beads to the composite mixed powder is controlled to be 1: 0.8, the ball milling time is 3 hours, and then taking out the premixed powder in the high-purity argon and standing for later use;
(2) grinding and polishing the surface of the beryllium-aluminum alloy to be treated, ultrasonically cleaning the surface of the beryllium-aluminum alloy by using analytically pure absolute ethyl alcohol and deionized water in sequence, and air-drying the surface of the beryllium-aluminum alloy for later use to obtain a beryllium-aluminum alloy substrate;
(3) in high-purity argon, pre-mixed composite powder with the thickness of about 1.0 mm is flatly paved on a beryllium-aluminum alloy substrate, and then the substrate is transferred into a vacuum sintering furnace. At vacuum degree of 5X 10-2Under the condition of Pa, preserving heat for 18 minutes at 545 ℃ and completing sintering to obtain a sintered preformed beryllium-aluminum alloy/premixed powder compound;
(4) transferring the beryllium-aluminum alloy/premixed powder composite into an electron beam furnace at 5.0 multiplied by 10-2Preheating the beryllium-aluminum alloy/premixed powder complex in the previous step to 500 ℃ under the Pa vacuum degree, preserving heat for 8 minutes, starting a power supply to perform electron beam surface remelting after the preheating is finished, and controlling the power of an electron beam to be 2.0kW and the light spot to be straightThe diameter is 7mm, the linear scanning speed is 12mm/s, and the remelting of the upper surface of the alloy is completed in a reciprocating "" path. Then introducing high-purity argon at a gas flow of 20L/min for auxiliary cooling to room temperature;
(5) transferring the beryllium-aluminum alloy substrate subjected to electron beam cladding to a vacuum heat treatment furnace, and vacuumizing to 3 multiplied by 10- 2And Pa, firstly heating to 505 ℃ at the speed of 12 ℃/min and preserving heat for 7 hours, then closing the power supply and cooling the furnace to 300 ℃, then re-feeding electricity and preserving heat for 2.5 hours, and cooling the furnace to room temperature after finishing.
Example 3:
a preparation method of a beryllium-aluminum alloy surface composite reinforced modified layer comprises the following steps:
1) preparing metal aluminum powder with the average particle size of about 30 micrometers, alumina powder with the average particle size of about 20 nanometers and beryllium oxide powder according to the parts by weight of the alumina powder, the nano beryllium oxide powder and the rest of the metal aluminum powder, carrying out dry ball milling and mixing in high-purity argon, wherein ball balls used for ball milling are corundum, the weight ratio of the ball balls to the composite mixed powder is controlled to be 1: 1.2, the ball milling time is 5 hours, and then taking out premixed powder in the high-purity argon and standing for later use;
(2) grinding and polishing the surface of the beryllium-aluminum alloy to be treated, ultrasonically cleaning the surface of the beryllium-aluminum alloy by using analytically pure absolute ethyl alcohol and deionized water in sequence, and air-drying the surface of the beryllium-aluminum alloy for later use to obtain a beryllium-aluminum alloy substrate;
(3) pre-mixed composite powder with the thickness of about 1.5 mm is flatly paved on a beryllium-aluminum alloy substrate in high-purity argon, and then the substrate is transferred into a vacuum sintering furnace. Under vacuum degree of 2X 10-2Under the condition of Pa, preserving heat for 10 minutes at the temperature of 600 ℃ and completing sintering to obtain a sintered preformed beryllium-aluminum alloy/premixed powder compound;
(4) transferring the beryllium-aluminum alloy/premixed powder composite into an electron beam furnace at a temperature of 3.0 multiplied by 10-2Preheating the beryllium-aluminum alloy/premixed powder composite in the previous step to 560 ℃ under the Pa vacuum degree, preserving heat for 5 minutes, starting a power supply to perform electron beam surface remelting after the completion of the preheating, controlling the power of the electron beam to be 2.5kW, the diameter of a light spot to be 10mm and the linear scanning speed to be 15mm/s, and completing the former compound zigzag pathRemelting the upper surface of the alloy, and introducing high-purity argon at the gas flow of 30L/min for auxiliary cooling to room temperature;
(5) transferring the beryllium-aluminum alloy substrate subjected to electron beam cladding to a vacuum heat treatment furnace, and vacuumizing to 3 multiplied by 10- 2And Pa, firstly raising the temperature to 520 ℃ at the speed of 15 ℃/min and preserving the temperature for 8 hours, then closing the power supply and cooling the furnace to 320 ℃, then re-feeding the power and preserving the temperature for 3 hours, and finally cooling the furnace to the room temperature.
Comparative examples 1 and 2:
comparative example 1 on the basis of example 3, no presintering was carried out after the powder spreading, and preheating and electron beam remelting were required after the powder spreading.
Comparative example 2 on the basis of example 3, the vacuum degree in the pre-sintering and electron beam remelting processes is lower than 1X 100Pa。
From the results of FIGS. 1-4, it can be seen that: the beryllium grains in example 1 generally exhibit a cellular-like crystalline morphology with an average grain size much lower than that of the beryllium phase grains of conventional cast beryllium-aluminum alloys due to rapid solidification of the melt after electron beam remelting. The oxide particles are distributed more uniformly in the matrix phase, with the aluminum phase being the main phase. The Vickers hardness value of the surface of example 1 is HV by testing0.589, higher than HV 45-60 of conventional cast beryllium-aluminum alloy. In example 3, because the oxide ratio, the electron beam power and the solidification rate are relatively higher, the separation degree of the beryllium and the aluminum phases is not obvious, the tissue consistency is higher, and the composite oxide particles are more uniformly distributed in the matrix. The Vickers hardness value of the alloy surface is HV0.5118, exhibits higher hardness and wear resistance.
Since the premixed powder is not sintered, the powder on the alloy surface is subjected to particle dissipation under the impact of vacuum pumping and electron beams, and oxide particles float on the upper surface of the melt, so that the condition that aluminum metal is used as a matrix and the oxide particles are agglomerated in a large scale is formed, as shown in fig. 3. In a poor vacuum environment, the surfaces of the metal aluminum powder and the alloy are oxidized seriously at high temperature, so that a surface remelting layer forms an evacuated flaky ceramic structure, and as shown in fig. 4, the alloy surface modification effect is poor.
The foregoing basic embodiments of the invention and their various further alternatives can be freely combined to form multiple embodiments, all of which are contemplated and claimed herein. In the scheme of the invention, each selection example can be combined with any other basic example and selection example at will. For example, fig. … … can also be regarded as a combination of the basic example and the option … …, fig. … … can also be regarded as a combination of the basic example and the option … …, and so on, which are not exhaustive, and those skilled in the art can recognize many combinations.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.