Research On Preparation,Microstructure And Properties Of Powder Metallurgy B₄C_p/SiC_p Hybrid Reinforced 2124 Aluminum Matrix Composites

The B₄C_preinforced aluminum matrix composites combine the advantages of the matrix and the B₄C_pparticle reinforcement,thereby having good comprehensive mechanical properties such as high strength and low density,and meet the needs of high-performance materials in the aerospace,defense industry and other fields.In this paper,B₄C_p/Si C_phybrid reinforced aluminum matrix composites with different B₄C_pvolume fraction are prepared through the process route of mechanical ball milling powder and argon protective sintering.The 2124Ti aluminum alloy independently designed by the laboratory is used as the matrix,1μm B₄C_pand30nm Si C_pare used as reinforcements.The influence of different preparation process,heat treatment and different reinforcement volume fractions on the structure and properties of composites was studied.The main contents and conclusions of this article are as follows:（1）The feasibility of ball milling and powder mixing process,as well as the influence of sintering time,sintering temperature,and hot extrusion process on the microstructure and mechanical properties of composite materials were explored.The main conclusions are as follows:The ball milling process of reinforcement wet milling-mixed wet milling-dry milling-secondary dry milling can prepare composite powders with uniform reinforcement dispersion,and composite powders with different microstructures can be prepared by controlling the timing of adding the matrix powder.From the perspective of microstructure,hardness,densification and other properties,the composites after 8h sintering is significantly better than 4h sintering.When the sintering time is 8h and the sintering temperature is in the range of 600～750℃,700℃is the best temperature for argon protective sintering.as the temperature increases,the hardness and densification of the sintered composites first increase and then decrease.The structure and performance of the material after sintering at 700℃×8h are the best,the hardness and densification are 224.6 HV and 85.5%,respectively.Extrusion under an extrusion process with an extrusion temperature of 520°C and an extrusion ratio of 7:1 can significantly increase the hardness and density of the material.After hot extrusion,the densification of the composites with a volume fraction of B₄C_pof 10%increases from 87.9%of the sintered state to 98.6%,and the hardness increases from 141.4HV to 172.5HV.The structure and properties of the composites were significantly improved.（2）Three different multi-stage solid solution processes（G1:480℃×2h+490℃×2h;G2:480℃×2h+490℃×2h+500℃×2h;G3:480℃×2h+490℃×2h+500℃×2h+510℃×2h）were used,and the effects of solid solution processes on the structure and properties of10%B₄C_p-2%Si Cp/2124Ti composites have been studied,and the optimal aging time of the materials after solid solution was explored.The results showed that:With the increase of the solution temperature and the solution time,the degree of solid solution increases,and the material obtains the best solution effect under the G3 solution process.The results show that the G3 solid solution process has the best effect on the improvement of composites properties.With the increase of solution temperature and solution time,the hardness of the composites after solid solution increases significantly.After aging at 185℃for 12 hours,the hardness reaches the peak,which is 23.6～50.6HV higher than the hardness before solution.The material obtains the best solution effect under the G3 solution process,and the hardness of the material reaches 244.4HV.With the increase of solid solubility,the electrical conductivity of the composites decrease;after three solid solution treatments and aging for 12 hours,the compressive strength of the composites has been greatly improved,which are 690MPa,750MPa and 765MPa,but the toughness of the composite decreases.After G3 solution treatment and aging for 12 hours,the compressive strength of the composite material reaches the maximum value of 765MPa,and its fracture strain is 8.04%.（3）The effects of different volume fractions（10%,15%and 20%）of B₄C_pon the structure and properties of B₄C_p-2%Si C_pparticle hybrid reinforced aluminum matrix composites were studied.The results showed:As the volume fraction of B₄C_pincreases,the difficulty of dispersion increases.Agglomeration of reinforcements appears in the composites with a volume fraction of B₄C_pof 20%;The increase of B₄C_pvolume fraction increases the dislocation densification inside the material,and the contribution of dislocations to strength increases;The hardness of the material first increases and then decreases with the increase of the B₄C_pvolume fraction.The composites with 15%B₄C_phave the highest hardness,which is 331.9HV;The electrical conductivity and densification of the material decrease gradually with the increase of B₄C_pvolume fraction;the compression fracture modes of the three materials are brittle fracture,and their toughness are relatively poor.As the volume fraction of B₄C_pincreases,the compressive strength of the composites first increase and then decrease,The composites with a volume fraction of B₄C_pof 15%has the highest compressive strength,which is 788MPa,and the fracture strain is 6.23%.In this paper,through a new process route of ball milling powder mixing-sintering-hot extrusion-strengthening and toughening heat treatment,using self-designed 2124Ti aluminum alloy as the matrix,adding B₄C_pand Si C_pas reinforcements,B₄C_p/Si C_pparticle hybrid reinforced aluminum matrix composites with uniform structure and excellent comprehensive performance was successfully prepared,and the best sintering process,heat treatment process and reinforcement content were explored,which can provide reference for the subsequent research on hybrid reinforced aluminum matrix composites.