Improving the mechanical properties of α + β titanium alloys by tailoring α″ nanotwins variants

Abstract

We employ Ti-3Al-5Mo-4.5 V (wt. %, α + β) alloy to investigate, for the first time, the evolution of α″ nanotwins at different aging temperatures in an α + α″ coexisting microstructure, as well as their influence on mechanical properties. The results demonstrate that {111}_α″ type Ⅰ nanotwins form to accommodate α″ lattice strain during low-temperature aging. Both the number proportion and area proportion of the type I nanotwins increase as the aging temperature rises from 300 °C to 350 °C. The relatively abundant pre-existing nanotwins in the samples aged at 350 °C significantly hinder the occurrence of stress-induced <211>_α″ type Ⅱ twinning transformation, leading to enhanced yield strength. This study provides critical insights into developing new Ti-alloys with superior strength/ductility.