Examination of Tensile Deformation and Void Nucleation Behaviors of Duplex Stainless Steel Using Nano-Indentation Hardness Test

The plastic deformation behavior in a uniaxial tensile test was examined by applying the nano-indentation hardness test to the ferrite-austenite duplex stainless steel. Each phase revealed the same hardness and a different work hardening ratio. The effect of the hardness difference in each phase on the void nucleation process was investigated by means of EBSD analysis. From the EBSD analysis, deformation twinning and deformation-induced martensitic transformation were observed in the austenite phase near the fracture surface. The hardness of austenite rose to a higher degree than that of ferrite, and showed an extremely-high value due to martensitic transformation. The void appeared mainly at the interface between the martensite induced by deformation and the ferrite phases. Thus the void nucleation was enhanced by the martensitic transformation which occurred at the location of higher equivalent strain of 1.5.