Microstructure and mechanical properties of in-situ hybrid reinforced (TiB+TiC)/Ti composites prepared by laser powder bed fusion

Abstract

To address the problems of insufficient strength and low hardness in pure titanium, a new Ti-B-C powder system was used to prepare in-situ hybrid reinforced (TiB+TiC)/Ti composites by laser powder bed fusion (LPBF) technology. The influence of different TiB/TiC ratios on the hybrid reinforcement was investigated. When the TiB/TiC ratio is 1:1, the best hybrid reinforcement effect is achieved and the mechanical interlocking structure is formed between TiB and TiC. The structures enhance the strength of (TiB+TiC)/Ti composites significantly. Subsequently, the microstructures and mechanical properties of (TiB+TiC)/Ti composites were investigated by adjusting different TiB+TiC contents. As the TiB+TiC content increases, the grains are refined significantly and transform into equiaxed grains eventually, the preferred orientation disappears. When the TiB+TiC content is too high, severe agglomeration of TiB+TiC occurs, resulting in less noticeable improvement in strength and a rapid decrease in plasticity. Finally, the heat treatment of (TiB+TiC)/Ti composites was carried out. TiB and TiC are uniformly distributed. TiC coarsens significantly, and TiB exhibits a dual-scale effect. The higher the heat treatment temperature, the more favorable it is to improve the plasticity of titanium matrix composites (TMCs). The TMC2 after HT950 has a tensile strength of 879 MPa and an elongation of 11.7%, exhibiting excellent comprehensive mechanical properties.