Novel two-scale network structured (TiBw + Ti2Cu)/Ti6Al4V composites: Design, microstructure, mechanical properties and fracture behavior

Abstract

Titanium matrix composites with homogeneous microstructures often exhibit inferior mechanical properties, thus severely restricting their applications for engineering-structural parts. Inspired by nature’s fine microstructures, we have in-situ constructed a novel two-scale structured (TiB_w + Ti₂Cu)/Ti6Al4V composites for significantly improve the mechanical properties of the Ti matrix, i.e., with the first-scale network reinforced by micro-TiB_w and the second-scale network reinforced by nano-Ti₂Cu. Average sizes of α-Ti were significantly refined with adding 2.53 vol% TiB_w, and in-situ formed TiB_w was favorable for formation of equiaxed α-Ti. At 293 K, yield strength and ultimate tensile strength (UTS) of (2.53 vol% TiB_w + 3.02 vol% Ti₂Cu)/Ti6Al4V composites were 1160 MPa and 1272 MPa, respectively, which were 47.2 % and 41.0 % higher than that of Ti6Al4V. Moreover, their maximum strength (514 MPa) is 27.4 % higher than that of Ti6Al4V alloy at 873 K. The remarkable increase in strength for the composites is attributed to fine-grain strengthening and precipitation-strengthening from Ti₂Cu nanoparticles, and high temperature strength is due to the pinning effect of TiB_w in the softened matrix and hinderance of flow in the matrix.