Atomic-scale understanding of martensitic transformation and transition-induced twinning in deformed Fe-Mn alloys

Abstract

In the present study, molecular dynamic simulation (MD) was used to investigate the plastic deformation process of the Fe-Mn alloys with different Mn contents. The influences of Mn contents ranging from 10% to 30% (at%) on the deformation behavior and the controlling mechanism of the Fe-base alloys were analyzed. The results show that phase transformations and {112} <111>_BCC deformation twinning occur in all Fe-Mn alloys but follow different deformation paths. In the Fe-10%Mn alloy the deformation twinning mechanism obeys the FCC-related path, the Fe-20%Mn alloy involves both the FCC- and HCP-related paths, and the deformation of the Fe-30%Mn alloy is dominated by the HCP-related twinning path. The addition of Mn can increase the stacking fault energy and retard the activation of slip systems as well as the formation of stacking faults. Thus, a higher content of Mn can delay the FCC→ε-martensite and the subsequent ε-martensite→BCC phase transition at the intersection of two ε-martensitic bands. Therefore, the addition of Mn alloying element increases the yield strength and reduces the elastic modulus of the Fe-Mn alloys. The formation of deformation twins will contribute to the work-hardening effect and delay the necking and fracture of alloys. It is expected that the results in the present study will provide theoretical reference for the design and optimization of high-performance steels.

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