The influences of strain and compressive stress on the α to ε phase transformation behavior in α-Mn steels were investigated by means of high-pressure torsion (HPT). In addition, the influence of Mn addition, i.e. 10, 12, 15 mass%Mn, which increases the stability of ε phase relative to α phase on it was also investigated.
The stabilization of ε phase in the 12 and 15 mass%Mn steels at ambient condition occurred via the application of HPT-straining in the ε phase state, but no ε phase was observed in the 10 mass%Mn steel. The fraction of ε phase increased with the strain and/or the compressive stress in the HPT-straining. This dependence on them was emphasized by the addition of Mn. In the HPT-processed specimens, the Burgers orientation relationship was observed between α and ε phases. This shows that the α phase transformed completely into the ε phase by the compressive stress in the HPT-straining and then the ε phase reverse-transformed partially into the α phase after unloading the compressive stress.
