Effect of deformation-induced martensitic transformation on nonuniform deformation of metastable austenitic steel

Mao, W.; Gong, W.   ; Kawasaki, Takuro   ; Harjo, S.   

The effect of the deformation-induced martensitic transformation (DIMT) on the Portevin-Le Chatelier (PLC) effect in Fe-24Ni-0.3C (wt%) metastable austenitic steel was investigated herein by using digital image correlation (DIC) technique combined with in-situ neutron diffraction. The DIMT and the PLC deformation were simultaneously observed by in-situ neutron diffraction and DIC, respectively. The results showed that the type of PLC bands changed from type A + B to type C after the DIMT occurrence (i.e., the PLC band behavior changed from propagation type to random static nucleation type, while the localized deformation suddenly and significantly increased). The DIC analysis demonstrated that the strain per PLC band did not immediately increase after the martensite formation. The remarked increase in the localized deformation was mainly attributed to the unusual temporary spatial aggregations of the type C PLC bands caused by the autocatalytic effect of the martensitic transformation.