Effect of Micro-Scaled Compositional Gradient on Microstructure of High-Strength Ti-W Composites

Abstract

Strength-ductility trade-off is a difficult challenge of structural materials. In this work, a precipitate-gradient Ti-W alloy with simultaneous high strength and high ductility was prepared by powder metallurgy and subsequent heat treatment. The precipitate-gradient structure was achieved by controlling the diffusion of W phase. The diffusion of W phase on microstructural evolution and strengthening mechanisms were investigated. The precipitate-gradient titanium alloy exhibits high strength, high ductility and superior strain hardening capability. It was found that the high strength was mainly caused by the solid strengthening of W atoms and the precipitation strengthening of α ’/ α ’’phases. Furthermore, the gradient structure could generate strong hetero-deformation induced (HDI) stress, which further enhanced the strength of the titanium alloy. The good ductility and superior strain hardening capability were attributed to the activation of multiple deformation modes around the gradient interface during plastic deformation, including planar dislocation sliding, stress-induced twinning (TWIP), and stress-induced martensite phase transformation (TRIP).

Keywords: precipitation, Gradient structure, Titanium alloy, strengthening mechanism, Deformation behavior