Investigation On Process Optimization And Structure Design Of TiB₂/Cu Composites Prepared By Powder Metallurgy

How to solve the contradiction between the electrical conductivity and mechanical properties of ceramic phase-reinforced copper matrix composites is the hotspot in current research.In this paper,Three aspects is considered to solve this contradiction by powder metallurgy:reaction system,powder mixing process and structural design.Firstly,changing the reaction system and the mixing process,and then conclude the relationship between the microstructure and the comprehensive properties of the material.Based on this conclusion,TiB2/Cu composites with heterogeneous reinforcements was prepared,and the effect of heterogeneity on the properties of the composites was studied.The phase constituents and microstructure characterization of the composites were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The hardness,electrical conductivity and tensile properties of the composites with different microstructures were tested.The main findings are as follows:(1)The TiB2/Cu composites were prepared by different reaction systems.It was found that the composite particles in the Cu-TiH2-B system were finer and more homogeneous than in CuXi-B system.and the reinforcement distribution follows a certain directionality.The comprehensive properties of the composites prepared by Cu-Ti-B system was found to be better than composites prepared by Cu-Ti-B system under the same process.(2)The TiB2/Cu composite powder is prepared by two kinds of mixing processes.The second phase in composite perpared by ball milling distributed more homogeneous and dispersed,and the mechanical properties of the material are more excellent,but the electrical conductivity is lower.In contrast,the TiB2/Cu composite obtained by the ball milling+mixing method has higher electrical conductivity,and the mechanical properties can be improved by subsequent cold rolling and annealing treatment.(3)On the basis of the above research,Cu powder was added in two steps to prepare heterogeneous TiB2/Cu composite,the microstructure is composed of reinforcement-rich zone and reinforcement-poor zone.As the mass percentage of the ball-milled Cu powder increases,the degree of heterogeneity of the reinforcement distribution in the composite material changes,and the microstructure of the composite material tends to be homogeneous,while the microscopic upper layer structure is more obvious.(4)As the mass percentage of Cu powder involved in ball milling increases,the conductivity of the heterogeneous TiB2/Cu composite decreases gradually,while the mechanical properties gradually increase,and the plasticity reaches the maximum when the mass percentage of the ballmilled Cu powder is 80%,the mechanical properties are the best at 95%.(6)The mechanical incoMPatibility between the reinforcement-rich zone and reinforcement-poor zone in heterogeneous TiB2/Cu composite results in strain distribution,which improves the ductility of the material,while the back stress reinforcement and work hardening at the interface improve the material’s mechanical properties.Because of the existence of the interface-affected zone,the optimal interfacial spacing exists between the enrichment zone and the depletion zone of the non-uniform structural composite,and the best mechanical properties can be obtained by changing the design.