A β-type titanium alloy with high strength and low elastic modulus achieved by spinodal decomposition

Abstract

In the present work, a Ti-40Zr-12Ta (in atom percent, at%) alloy with the spinodal decomposition was designed based on the isothermal section of the Ti-Zr-Ta ternary phase diagram. The alloy was first solid solution treated at 1000 °C and then cold rolled with a thickness reduction of 70% at room temperature. After that, the as-rolled samples were annealed at the temperatures ranging from 500 °C to 900 °C, and the effects of annealed temperature on the microstructure and mechanical properties were investigated. It is found that the spinodal decomposition occurred in the alloy at the temperature ranging from 500 °C to 700 °C, leading to the formation of the periodically distributed Ta-rich (β1) and Ta-lean phases (β2). The as-rolled Ti-40Zr-12Ta alloy exhibited a relative high strength due to the work hardening and solid solution strengthening. Annealing treatment at 500 °C promoted the strength of the alloy but significantly decreased its plasticity due to the formation of nano-scale isothermal ω phases. The sample annealed at 700 °C exhibited good tensile mechanical properties, and the modulated structure introduced by spinodal decomposition and TRIP effect contribute to the improvement of its strength and plasticity.