Metastable Austenite in 17-4 Precipitation-Hardening Stainless Steel Produced by Selective Laser Melting

A 17-4 precipitation-hardening stainless steel produced by selective laser melting contains 72% metastable and heavily faulted austenite and 28% highly dislocated and twinned martensite. The mechanical behavior is characterized by exceptional work hardening and a two-step plastic field, which are due to the strain-induced transformation of austenite and to the structural characteristics of the deformed austenite and martensite. Both phases tend to accumulate stacking faults in the first step and twins in the second.