Tailoring the mechanical properties of titanium alloys via plasticity induced transformations

Abstract

Titanium alloys possess good corrosion properties, high temperature stability and high strength-to-weight ratio. However, they fall short in providing the optimum strength-ductility relation in the most demanding structural applications, including the aerospace sector. Inspired by the possibility of enhancing the strength-ductility relation in steels through the TRIP effect, the thesis elucidates at: i) identifying and quantifying the key factors that effectively control and/or promote such effect (termed here as Plasticity induced Transformation in Titanium alloys (PiTTi)), and exploring the plausible property improvements it may lead in metastable beta titanium alloys, through experimentation; ii) theoretically optimizing the key factor, Ms temperature, by proposing a thermodynamic based model for prediction of martensite formation (i.e., Ms temperature) in both binary and multi-component beta titanium alloys with effective validation; and iii) proposing, by controlling the mentioned key factors that effectively promote PiTTi effect, a novel theoretical alloy design methodology that lead to achieving new grades of titanium alloys for potentially improved properties.