Effects of solution-aging treatments on microstructure features, mechanical properties and damage behaviors of additive manufactured Ti–6Al–4V alloy

Abstract

Hot isostatic pressing (HIPing) treatment was generally carried out to eliminate possible defects and to homogenize the microstructure for Ti–6Al–4V alloy fabricated by the Electron beam rapid manufacturing (EBRM) process. But the HIPed alloy with relative coarse lamellar microstructure exhibited a low strength compared to the as-built one. Post solution-aging treatments were necessary to optimize the HIPed alloy's tensile properties. So far, the relationship between the heat-treated microstructure features and corresponding mechanical properties of EBRM-produced Ti–6Al–4V has not been completely understood. Therefore, in the present work, solution-aging treatments under various solution temperatures (930 °C–990 °C) were applied to the HIPed Ti–6Al–4V produced by the EBRM, and the corresponding microstructures and mechanical properties were investigated. The results showed that solution-aging treatments could increase the HIPed alloy's tensile strength but decrease its ductility. With increasing solution temperature, the tensile strength presented an upward tendency until to 980 °C, whereas a decrease after 990 °C solution treatment. The variation in tensile properties was caused by the microstructures evolved with solution temperatures. In-situ tensile results showed that the deformation and damage behaviors of the alloy were also highly affected by the solution temperatures. Owning to a decrease of content of the αp with increase of solution temperature, the alloy at high solution temperature presented superior resistance of crack initiation but inferior resistance of crack growth than that at low solution temperature.