Effect of Heat Treatment on Gradient Microstructure and Tensile Property of Laser Powder Bed Fusion Fabricated 15-5 Precipitation Hardening Stainless Steel

Abstract

This work investigated the gradient microstructure evolution and tensile property of LPBF fabricated 15-5 precipitation hardening stainless steel in post-process direct ageing (DA) and solution treating & ageing (STA). The varied microstructures for austenite and small-sized oxide inclusions at different sample heights in the as-built (AB) condition was generally preserved after DA treatment. However, austenite was almost disappeared, and oxide particle grew significantly after the STA treatment. As a result, the tensile property differences in sample top and bottom for AB and DA conditions did not occur in the STA samples. For the influence of post-process heat treatment, the STA condition had the highest yield strength due to the highest volume fraction of nano-sized Cu precipitates. However, the DA specimen had the highest ultimate tensile strength and elongation owing to the considerable amount of austenite phase and associated transformation induced plasticity effect.