Towards work-hardenability of Ti-6Al-4V through a quenching and partitioning approach

Abstract

In this work, the work-hardening ability of Ti-6Al-4V alloy was investigated using a quenching and partitioning strategy on dual-phase Ti-6Al-4V samples. As recently reported [1], it is known that a sub-transus thermal treatment followed by water quenching are able to generate a dual phaseα + α’ microstructure with a remarkable work-hardening coupled with an interesting balance between strength and ductility. Based on this statement, several heat treatments at various subtransus temperatures were performed on as-forged Ti-6Al-4V. In such a way, the respective volume fraction of each phase along with the size and the distance to the equilibrium composition of the quenched martensite are taken as microstructural variables to decompose the work hardenability of dual-phase Ti-6Al-4V alloys into respective contributions. Then, annealing of the metastable α + α’ microstructure was performed to trigger the α’ martensite decomposition, involving a partitioning of the alloying elements. The present investigation was carried out on wrought material.The quenching and partitioning parameters led to a wide range of mechanical properties and associated work-hardening behaviour. The as-quenched and further annealed microstructures were characterized by Scanning Electron Microscopy (SEM). The resulting mechanical properties were discussed and compared to those of as-forged material.