Microstructural and phase evolution of Ti6Al4V in electron beam wire additive manufacturing and on the subtransus quenching and normalization

Abstract

Structural evolution of electron beam wire additively manufactured Ti–6Al–4V subjected to quenching and normalization from the subtransus temperatures 900 °C has been studied. Different phase states and structures have been obtained in the as-built sample such as grain-boundary (allotriomorphic) α-GB, Widmanstatten (basket-weave) α/β as well as α/α′′ and α/α2. Quenching resulted in retaining the α-GB and α/α2 structures while α/β transformed into α/α′. Normalization caused formation of α′′-Ti and ω-Ti phases in addition to the primary α. The α-Ti variant selection depended on the intensity of heating so that the number of Type-4-2 grain boundaries with misorientation angles 60, 60.8, 63.3° increased from the as-built to normalized sample. Quenching provided improvement of both tensile strength and plasticity.