Copper matrix composite with bimodal microstructures fabricated by liquid nitrogen temperature rolling

Abstract

Liquid nitrogen temperature (LNT) rolling at a high strain rate was applied to in-situ TiB₂/Cu composites fabricated by powder metallurgy. An artificially controlled heterogeneous distribution of TiB₂ particles in a Cu matrix leads to bimodal microstructures in the LNT-rolled composites, i.e. reinforcement-rich regions are constituted by in-situ formed TiB₂ particles and nano-Cu grains (about 25 nm), while reinforcement-poor regions are mainly composed of heavily deformed ultrafine Cu grains (about 0.5 µm). Compared with TiB₂/Cu composites processed by normal rolling, LNT-rolled TiB₂/Cu composites with heterogeneous microstructures exhibit good overall performance with high ultimate tensile strength (594 MPa), high elongation (6.3%), high electrical conductivity (82.6% International Annealed Copper Standard) and improved thermal stability, which is favourable for electrical and electronic device applications.