Friction stir processing of a metastable β titanium alloy in β and α+β phase fields

Abstract

A metastable β titanium alloy Ti–5Al–5Mo–5V–3Cr (Ti-5553) was friction stir processed (FSP) in both the β and α+β phase fields. Homogenous microstructures were obtained in both phase fields by adjusting FSP parameters. The mean β grain size after FSP varied from 15 to ~0.7 μm from the single-phase β to α+β conditions, respectively. At the α+β conditions, a near-globular α phase (50–200 nm in size) was observed. Microstructure and microtexture evolution in β and α+β conditions were investigated with the aid of scanning and transmission electron microscopy. Ultra-fine intra-granular α and duplex α microstructures were generated at both conditions by duplex aging of the FSP samples. The FSP alloys display excellent combinations of strength and ductility.