Balancing strength and ductility by controllable heat-treatment twinning in a near β-Ti alloy

Abstract

A new thermomechanical process was applied to a near-β Ti-5Al-5Mo-5V-1Cr-1Fe alloy to induce twinning. The resulting combination of ultrafine grains and heat-treatment twins endowed the alloy with excellent tensile strength (1544 MPa) and elongation (13%). β-Field cross-rolling formed micro-sized β grains, and ultrafine α particles precipitated from pre-existing dense dislocation structures and martensites. α-Twinning occurred during heat treatment and continuously evolved with the ongoing heat treatment time. A precisely controlled heat treatment time enabled the distribution of nanosized twins throughout the α laths, simultaneously improving strength and ductility. The results of this study pave the way for the development of customised titanium alloys with significantly improved mechanical properties.

Keywords

• Ti alloy
• Ultra-fine grain
• Heat-treatment twin
• Cross-rolling
• Mechanical properties