Effect of heat treatments on pore morphology and microstructure of laser additive manufactured parts

Abstract

The slit-shaped, lack-of-fusion pores (LFPs) persistent in the additively manufactured (AM) metals are detrimental to their fatigue resistance due to the associated stress concentrations at the edges. Postbuild treatments, such as hot isostatic pressing (HIP), are routinely used to eliminate pores resulting in, however, inconsistent improvements in fatigue performance. This work critically examines the effectiveness of HIP to eliminate such pores in AM Ti-6Al-4V. In addition, conventional heat treatment (HT) is proposed as a candidate remedial process to alleviate the harmful effects of the LFPs. Specifically, the spheroidization effect of HT on the sharp edges of the LFPs is investigated. Lastly, the effect of HT and HIP on the microstructure is carefully analyzed, safeguarding the beneficial refined microstructure of AM Ti-6Al-4V.