Controlling Phase Composition in Selective Laser Melted Stainless Steels

Commercially important stainless steels can be austenitic or martensitic and this phase composition fundamentally controls the mechanical properties of the material. With selective laser melting (SLM), 17-4 stainless steel can be produced in either phase depending on powder composition, SLM conditions and post-build heat treatment. This behavior is examined using optical and electron microscopy and high temperature x-ray diffraction in order to better understand the formation of metastable austenite and its transformation to martensite. Control of phase composition can produce a material with either extremely large strain-to-failure or high yield strength and can provide a method for completely eliminating residual stress.