Influence of prior-β-grain size on tensile strength of a laser-deposited α/β titanium alloy at room and elevated temperatures

The influence of prior-β-grain (PBG) size on the tensile behavior of a laser-deposited α/β Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy was investigated to reveal the strengthening mechanism of PBGs. Results show that the strength increases with increasing PBG size. This special coarse-PBG strengthening predominantly depends on the strong constraints resulting from the strain incompatibility among PBGs rather than PBG boundary resistance to dislocation motion. With increasing PBG size, increasing constraints are developed in the adjacent PBGs, and thus the applied stress needed to maintain the compatible deformation among these PBGs increases. In particular, the strengthening effect is not significantly affected by increasing temperature, which reveals a potential strengthening method that can strengthen a laser-deposited α/β Ti alloy at room and elevated temperatures simultaneously by controlling its PBG size.