Preparation method of dual-mode configuration B4C / Al composite material with alternate soft and hard areas

Abstract

The invention discloses a preparation method of a dual-mode configuration B4C / Al composite material with alternate soft and hard regions. The invention relates to the field of particle reinforced metal matrix composite material preparation, in particular to a preparation method of a dual-mode configuration B4C / Al composite material with alternate soft and hard areas. The problems that a traditional B4C / Al composite material of a uniform structure is poor in plasticity and has risks in the service process, and a B4C / Al composite material of a dual-mode structure is difficult to prepare and large in size are solved. The method comprises the steps that coarse spherical Al powder, fine spherical Al powder and fine B4C powder are mixed and then subjected to hot pressed sintering, and an independent microstructure that soft Al is distributed on continuous hard B4C / Al can be obtained. And then the composite material is subjected to hot extrusion, so that the soft Al and the hard B4C / Al are arranged and lengthened in the extrusion direction, and a dual-mode configuration microstructure with alternately distributed soft and hard areas is formed.

Description

Technical Field

[0001] The invention relates to the field of preparation of particle-reinforced metal-based composite materials, and in particular to a preparation method of a dual-mode B4C / Al composite material with alternating soft and hard regions. Background Art

[0002] B4C / Al composites have the advantages of low density, high strength, wear resistance and impact resistance. They are expected to replace aluminum alloys and become the preferred material for key high-tech structural parts such as aircraft, automobiles, and spacecraft. They are of great significance to the development of national defense, aerospace, transportation and other fields. However, traditional B4C / Al composites bear the load through uniformly distributed B4C particles and hinder the slip of matrix dislocations, causing a large amount of dislocations to accumulate at the reinforcement / matrix interface, resulting in serious stress concentration. Therefore, although the strength of B4C / Al composites is improved compared to aluminum alloys, the elongation is significantly reduced, and the material often undergoes brittle fracture, which greatly increases the risk of service. Therefore, in order for B4C / Al composites to serve safely in actual applications, they need to have a certain degree of plasticity. This poses a challenge to the strength-plasticity coordination of B4C / Al composites.

[0003] Bimodal configuration is a microstructure constructed in nanocrystalline metals in recent years. It refers to a configuration in which soft coarse-grained areas are embedded in hard nanocrystalline areas in metal materials, forming a configuration in which soft coarse-grained areas and hard nanocrystalline areas are alternately distributed. Compared with nanocrystalline metals, bimodal configuration metals maintain high tensile strength and have an elongation comparable to that of coarse-grained metals. Therefore, inspired by bimodal configuration metals, bimodal configuration can be constructed in B4C / Al composites to improve their strength-plasticity coordination. By regulating the distribution of B4C particles, particle-rich and poor areas appear in the composite material. Since B4C promotes matrix recrystallization and hinders grain growth, fine grains are found in the particle-rich area, while coarse grains are found in the particle-poor area, forming an alternating distribution of fine and coarse grain areas similar to bimodal configuration metals. However, the current preparation process of bimodal configuration B4C / Al composites is complex and the preparation cycle is long, which is not suitable for industrial-scale preparation. In addition, there are certain difficulties in regulating the width of the soft zone of the dual-mode B4C / Al composite material, which makes it difficult to fully exert the coordinated deformation effect of the soft and hard zones. Therefore, a new preparation method is needed to achieve large-scale preparation of dual-mode B4C / Al composite materials and promote their engineering applications. Summary of the invention

[0004] The present invention aims to solve the problems of poor plasticity of conventional uniform structure B4C / Al composite materials, risks in the service process, and difficulty in preparing dual-mode B4C / Al composite materials and difficulty in preparing them in large sizes, and to provide a method for preparing a dual-mode B4C / Al composite material with alternating soft and hard regions.

[0005] A method for preparing a dual-mode B4C / Al composite material with alternating soft and hard regions is specifically carried out in the following steps:

[0006] 1. Powder ball milling: coarse spherical Al powder, fine spherical Al powder and fine B4C powder are ball milled in an argon atmosphere; the ball milled powder is taken out from a glove box and vacuum packaged to obtain a B4C / Al mixed powder;

[0007] 2. Cold pressing of mixed powder: B4C / Al mixed powder is loaded into a steel mold, and then a certain pressure is applied at room temperature, and the cold pressed preform is obtained after the pressure is maintained for a certain period of time;

[0008] 3. Hot pressing sintering of B4C / Al composite material: the cold pressed preform is placed in a furnace, filled with argon and kept at high temperature for a certain period of time, then high pressure is applied and kept for a certain period of time, cooled naturally to room temperature, and demolded to obtain a B4C / Al composite material block;

[0009] 4. Hot extrusion of B4C / Al composite material: The B4C / Al composite material block is placed in a mold for hot extrusion, and the extruded rod is naturally cooled to room temperature to obtain a double-mode configuration B4C / Al composite material extruded rod.

[0010] Beneficial effects of the present invention:

[0011] The present invention provides a dual-mode B4C / Al composite material with alternating soft and hard regions. The fine B4C powder, fine spherical Al powder and coarse spherical Al powder are mixed to obtain a mixed powder in which coarse spherical Al powder is encapsulated by fine B4C / Al mixed powder. The fine B4C / Al mixed powder is sintered into a hard B4C / Al composite material by hot pressing and sintering, and the coarse spherical Al powder is sintered into a soft Al matrix. By hot extrusion, the hard B4C / Al composite material and the soft Al matrix are both elongated and oriented along the extrusion direction to form a dual-mode configuration in which soft and hard regions are alternately distributed. During the tensile deformation process, the soft region bears the main plastic strain and relieves the stress concentration at the B4C / Al interface in the hard region. The hard region suppresses the yield of the soft region and improves the work hardening ability of the soft region, so that the composite material has both high strength and high plasticity.

[0012] The preparation method of the dual-mode B4C / Al composite material with alternating soft and hard regions provided by the present invention is simple and effective, with cheap raw materials, short preparation cycle, and not limited by the size of the reinforcement, and can meet the needs of industrial production. By changing the extrusion ratio, the width of the soft region can be accurately controlled, thereby adjusting the mechanical properties of the dual-mode B4C / Al composite material to meet the needs under different load environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1The reinforcement and grain distribution photos of the dual-mode B4C / Al composite material obtained in Example 1;

[0014] Figure 2 The reinforcement and grain distribution photos of the dual-mode B4C / Al composite material obtained in Example 2;

[0015] Figure 3 The engineering stress-strain curve of the dual-mode B4C / Al composite material obtained in Example 1;

[0016] Figure 4 This is the engineering stress-strain curve of the dual-mode B4C / Al composite material obtained in Example 2. DETAILED DESCRIPTION

[0017] Specific implementation method 1: In this implementation method, a preparation method of a dual-mode B4C / Al composite material with alternating soft and hard regions is specifically carried out in the following steps:

[0018] 1. Powder ball milling: coarse spherical Al powder, fine spherical Al powder and fine B4C powder are ball milled in an argon atmosphere; the ball milled powder is taken out from a glove box and vacuum packaged to obtain a B4C / Al mixed powder;

[0019] 2. Cold pressing of mixed powder: B4C / Al mixed powder is loaded into a steel mold, and then a certain pressure is applied at room temperature, and the cold pressed preform is obtained after the pressure is maintained for a certain period of time;

[0020] 3. Hot pressing sintering of B4C / Al composite material: the cold pressed preform is placed in a furnace, filled with argon and kept at high temperature for a certain period of time, then high pressure is applied and kept for a certain period of time, cooled naturally to room temperature, and demolded to obtain a B4C / Al composite material block;

[0021] 4. Hot extrusion of B4C / Al composite material: The B4C / Al composite material block is placed in a mold for hot extrusion, and the extruded rod is naturally cooled to room temperature to obtain a double-mode configuration B4C / Al composite material extruded rod.

[0022] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the particle size of the coarse spherical Al powder in step 1 is 40-200 μm, and the volume fraction of the coarse spherical Al powder is 20-50%. Others are the same as specific embodiment 1.

[0023] Specific implementation method 3: This implementation method is different from the specific implementation method 1 in that the particle size of the fine spherical Al powder in step 1 is 1 to 10 μm. The rest is the same as the specific implementation method 1.

[0024] Specific embodiment 4: This embodiment is different from specific embodiment 2 in that: the coarse spherical Al powder in step 1 is one of 1xxx, 2xxx, 5xxx, 6xxx or 7xxx. The rest is the same as specific embodiment 2.

[0025] Specific embodiment 5: This embodiment is different from specific embodiment 3 in that the fine spherical Al powder in step 1 is one of 1xxx, 2xxx, 5xxx, 6xxx or 7xxx. The rest is the same as specific embodiment 3.

[0026] Specific embodiment 6: This embodiment is different from specific embodiment 1 in that: the ball milling process in step 1 is: the ball-to-material ratio is 1:1, 3:1 or 5:1, the ball milling speed is 150-300 rpm, and the ball milling time is less than 5 hours. Others are the same as specific embodiment 1.

[0027] Specific implementation method 7: This implementation method is different from the specific implementation method 1 in that the particle size of the fine B4C powder in step 1 is 1-5 μm, and the volume fraction of the fine B4C powder is 10-20%. The rest is the same as the specific implementation method 1.

[0028] Specific embodiment 8: This embodiment differs from specific embodiment 1 in that the pressure in step 2 is 100-300 MPa, and the holding time is greater than 5 minutes. The rest is the same as specific embodiment 1.

[0029] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that: the high temperature in step 3 is 600-630°C, the holding time is 3-5h, the high pressure is 500-700MPa, and the holding time is greater than 10min. Others are the same as specific embodiment 1.

[0030] Specific embodiment 10: This embodiment differs from specific embodiment 1 in that: the hot extrusion temperature in step 4 is 450-500°C, the holding time is 1-2h, the extrusion speed is 0.25-0.75m / min, and the extrusion ratio is 5:1, 7:1, 9:1, 13:1 or 16:1. Others are the same as specific embodiment 1.

[0031] The effect of the present invention is verified by the following experiments:

[0032] Embodiment 1:

[0033] The preparation method of a dual-mode B4C / Al composite material with alternating soft and hard regions in this embodiment is specifically carried out in the following steps:

[0034] 1. Powder ball milling: 55.87g of 40μm spherical 7075Al powder, 33.52g of 10μm spherical 7075Al powder and 10.02g of 5μm B4C powder were ball milled in argon atmosphere. The ball milling process was: ball to material ratio 3:1, ball milling speed 200rpm, ball milling time 3h;

[0035] 2. Cold pressing of mixed powder: the B4C / 7075Al mixed powder is placed in a steel mold, and then a pressure of 300 MPa is applied, and the pressure is maintained for 5 minutes to obtain a cold pressed preform;

[0036] 3. Hot pressing sintering of B4C / Al composite material: the B4C / 7075Al cold pressed preform was kept at 600°C for 3 hours, then a pressure of 700 MPa was applied and kept for 10 minutes, and the preform was naturally cooled to room temperature, and a B4C / 7075Al composite material block was obtained after demolding;

[0037] 4. Hot extrusion of B4C / Al composite material: The B4C / 7075Al composite material block is placed in an extrusion die, kept at 470°C for 1 hour, and then hot extruded with an extrusion speed of 0.75m / min and an extrusion ratio of 9:1; the extruded rod is naturally cooled to room temperature to obtain a dual-mode configuration B4C / 7075Al composite material extruded rod.

[0038] Figure 1 The reinforcement and grain distribution photos of the dual-mode B4C / 7075Al composite material obtained in Example 1 show the presence of a hard region enriched with B4C and a soft region without B4C distribution. The grain size in the hard region is small, about 3 μm, while the grain size in the soft region is large, about 9 μm, and the hard and soft regions are alternately distributed and elongated along the extrusion direction. The width of the soft region is about 13.5 μm, and there are no defects such as pores and inclusions.

[0039] Figure 3 The engineering stress-strain curve of the dual-mode B4C / 7075Al composite material obtained in Example 1 shows that its yield strength is about 450MPa, its tensile strength is about 600MPa, and its elongation is close to 10%. Compared with the traditional uniform structure B4C / 7075Al composite material, its strength is almost not reduced, but its elongation is significantly improved, even comparable to that of 7075Al.

[0040] Embodiment 2:

[0041] The preparation method of a dual-mode B4C / Al composite material with alternating soft and hard regions in this embodiment is specifically carried out in the following steps:

[0042] 1. Powder ball milling: 55.87g of 40μm spherical 7075Al powder, 33.52g of 10μm spherical 7075Al powder and 10.02g of 5μm B4C powder were ball milled in an argon atmosphere; the ball milling process was: ball-to-material ratio 3:1, ball milling speed 200rpm, ball milling time 3h;

[0043] 2. Cold pressing of mixed powder: the B4C / 7075Al mixed powder is placed in a steel mold, and then a pressure of 300 MPa is applied, and the pressure is maintained for 5 minutes to obtain a cold pressed preform;

[0044] 3. Hot pressing sintering of B4C / Al composite material: The B4C / 7075Al cold pressed preform was kept at 600°C for 3 hours, then a pressure of 700MPa was applied and kept for 10 minutes, and then naturally cooled to room temperature. After demolding, a B4C / 7075Al composite block was obtained;

[0045] 4. Hot extrusion of B4C / Al composite material: Place the B4C / 7075Al composite material block into the extrusion die, keep it at 470°C for 1 hour, and then hot extrude it with an extrusion speed of 0.75m / min and an extrusion ratio of 5:1; naturally cool the extruded rod to room temperature to obtain a dual-mode configuration B4C / 7075Al composite material extruded rod.

[0046] Figure 2 The reinforcement and grain distribution photos of the dual-mode B4C / 7075Al composite material obtained in Example 2 show that there are hard areas enriched with B4C and soft areas without B4C distribution. The grain size in the hard area is small, about 3μm, while the grain size in the soft area is large, about 13μm, and the hard and soft areas are alternately distributed and elongated along the extrusion direction. The width of the soft area is about 27μm, and there are no defects such as pores and inclusions.

[0047] Figure 4 The engineering stress-strain curve of the dual-mode B4C / 7075Al composite material obtained in Example 2 shows that its yield strength is about 425MPa, its tensile strength is about 580MPa, and its elongation is close to 9%. Although the strength and elongation are both reduced compared with Example 1, its coordination of strength and plasticity is still better than that of the traditional uniform structure B4C / 7075Al composite material, showing obvious mechanical performance advantages.

Claims

1. A method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions, characterized in that The preparation method of the dual-mode B4C / Al composite material with alternating soft and hard regions is specifically carried out in the following steps:

1. Powder ball milling: coarse spherical Al powder, fine spherical Al powder and fine B4C powder are ball milled in an argon atmosphere; the ball milled powder is taken out from a glove box and vacuum packaged to obtain a B4C / Al mixed powder; 2. Cold pressing of mixed powder: B4C / Al mixed powder is loaded into a steel mold, and then a certain pressure is applied at room temperature, and the cold pressed preform is obtained after the pressure is maintained for a certain period of time; 3. Hot pressing sintering of B4C / Al composite material: the cold pressed preform is placed in a furnace, filled with argon and kept at high temperature for a certain period of time, then high pressure is applied and kept for a certain period of time, cooled naturally to room temperature, and demolded to obtain a B4C / Al composite material block; 4. Hot extrusion of B4C / Al composite material: The B4C / Al composite material block is placed in a mold for hot extrusion, and the extruded rod is naturally cooled to room temperature to obtain a double-mode configuration B4C / Al composite material extruded rod.

2. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that In step 1, the particle size of the coarse spherical Al powder is 40 to 200 μm, and the volume fraction of the coarse spherical Al powder is 20 to 50%.

3. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that The particle size of the fine spherical Al powder in step 1 is 1 to 10 μm.

4. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 2, characterized in that The coarse spherical Al powder in step 1 is one of 1xxx, 2xxx, 5xxx, 6xxx or 7xxx.

5. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 3, characterized in that The fine spherical Al powder in step 1 is one of 1xxx, 2xxx, 5xxx, 6xxx or 7xxx.

6. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that The ball milling process in step 1 is as follows: the ball-to-material ratio is 1:1, 3:1 or 5:1, the ball milling speed is 150-300 rpm, and the ball milling time is less than 5 hours.

7. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that In step 1, the particle size of the fine B4C powder is 1-5 μm, and the volume fraction of the fine B4C powder is 10-20%.

8. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that The pressure in step 2 is 100-300 MPa, and the pressure holding time is greater than 5 minutes.

9. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that In step 3, the high temperature is 600-630° C., the holding time is 3-5 hours, the high pressure is 500-700 MPa, and the holding time is greater than 10 minutes.

10. The method for preparing a dual-mode B4C / Al composite material having alternating soft and hard regions according to claim 1, characterized in that In step 4, the hot extrusion temperature is 450-500° C., the holding time is 1-2 hours, the extrusion speed is 0.25-0.75 m / min, and the extrusion ratio is 5:1, 7:1, 9:1, 13:1 or 16:1.

Images