Characterization of Microstructure and Mechanical Properties of Ti-6Al-4V Alloy after Cyclic Heat Treatment

Abstract

A cost-effective approach which consists of cyclic heat treatment (CHT) and annealing is used to refine the coarse lamellar structure of as-cast Ti-6Al-4V alloy. The coarse lamellar microstructure was significantly refined after the CHT process, α lamellae were broken up while the original orientations of α lamellae were maintained. After annealing treatment, a basketweave microstructure was achieved in Ti-6Al-4V alloy, and the formation of globular α grains was observed. The microstructure refinement mechanisms during CHT and annealing are mainly considered to be break-up of lamellar structure and static recrystallization. The room temperature mechanical properties of Ti-6Al-4V alloy were significantly improved. The microhardness of Ti-6Al-4V alloy increased from 306 HV to 402 HV. The values of yield strength (YS) and ultimate tensile strength (UTS) increased from 734 MPa and 740 MPa to 911 MPa and 1010 MPa, respectively. The value of ductility increased from 1.1 % to 3.3 %.