Hot isostatic pressing (HIP) to achieve isotropic microstructure and retain as-built strength in an additive manufacturing titanium alloy (Ti-6Al-4V).

Abstract

Hot isostatic pressing (HIP) treatments are traditionally used to seal internal porosity, because defects exist in as-built Ti-6Al-4V parts produced by electron-beam melting powder-bed fusion. Standard HIP treatment of Ti-6Al-4V parts results in decreased strength due to coarsening of the microstructure. We present a new HIP strategy with the following steps: hold above the β-transus, rapid quenching, and tempering. This new HIP treatment seals internal porosity, causes a columnar-to-equiaxed transition in morphology of prior-β grains, changes the α lath aspect ratio, removes microstructural heterogeneities and matches the yield and ultimate tensile strength of the as-built condition.