Microstructure and crystallographic phase sensitivity to process parameters in a bespoke PBF-LB 17-4 PH alloy

17-4 PH stainless steel made by powder bed fusion – laser beam (PBF-LB) has exceptional strength and ductility, brought about by transformation induced plasticity (TRIP). Here, we present an investigation into how PBF-LB laser energy density influences the microstructure, content of retained FCC austenite and the mechanical properties of a bespoke 17-4 PH alloy. X-ray diffraction experiments with in situ tensile loading were carried out to track the development of TRIP behaviour. Ex situ analysis provided microstructure and texture in the undeformed and deformed conditions. We found that the microstructure and phase composition are sensitive to the laser energy density ( E L ) during fabrication and, by exploring the process window, it is possible to vary the evolution of the material properties upon plastic deformation. Material made with a low- E L of 0.29 J/mm comprised 11.1% retained austenite, compared with just 3.8% when E L was raised to 0.67 J/mm. Consequently, the yield strength of the low- E L material was 44.6% lower than that of the high- E L material. This provides an opportunity to tune the properties of 17-4 PH stainless steel made by PBF-LB, with the aim creating high energy absorbing structures.