Study On Microstructure And Properties Of In-situ TiB₂/Cu Composites Prepared By Rapid Solidification

It is well known that the mechanical properties and electrical properties of copper alloys are contradictory.How to improve the mechanical properties of copper alloys on the basis of ensuring their electrical properties has become a key point in the research of copper alloys.In this paper,TiB2/Cu composites were prepared by in-situ reaction and rapid solidification,and a kind of copper matrix composites with excellent comprehensive properties was expected to be obtained by means of preliminary densification.In order to measure the effect of in situ reaction and rapid solidification on composites,two methods,in situ reaction spray deposition and in situ reaction gas atomization,were designed to prepare composite billet and composite powder,respectively.The effect of reaction degree on composites was studied by deposition billet,and the effect of solidification rate on composites was studied by composite powder.The results show that:(1)The design of graphite mould will directly affect the mixing and reaction degree of Cu-Ti alloy melt and Cu-B alloy melt,thus indirectly affect the structure and properties of composites.Poor reaction degree will lead to uneven macroscopic properties of the deposited billet;Excessive reaction will lead to a trend distribution of the second phase in the alloy melt and a gradient distribution of the second phase in the longitudinal direction of the deposited billet;Only when the two melts meet and react adequately,the melt enters the next atomization state,can the composites with uniform distribution of the second phase and fine particles be obtained.(2)With the increase of the content of reinforcing phase,the electrical conductivity and hardness of the deposited billet decreased and increased.After cold rolling deformation,the mechanical properties of the deposited billet are greatly improved,and the conductivity first increases and then decreases.Under the action of cold deformation,the microstructure of the deposited billet is streamlined,and the second phase clusters and some large-scale particles are fragmented,and the whole body is homogenized.Streamlined structure and broken particles have a positive contribution to the tensile properties of the composites.The fracture morphology of the composites is a typical ductile fracture mode-dimples.(3)the composite powder is mainly spherical,with a small amount of special-shaped powder and hollow powder.The special-shaped powders are twinning,satellite,entrapped,wrapped,hemispherical,near-spherical,the pores in hollow powder decrease with the decrease of powder size;and there are two kinds of powders:cu3Ti phase and TiB2 phase in the composite powder.(4)the cooling rate of powder is calculated based on equipment parameters and solidification structure of powder,and the results of the two methods confirm each other.The cooling rate of powder is 103-105k/s under the experimental condition,and the particle size of powder decreases gradually with the increase of cooling rate.The solidified structure changes from dendrite to cellular crystal.