Modulus characteristics during the γ→ε martensitic transformation in Fe–Mn–Si–Cr–N alloys

The temperature dependences of internal friction and modulus were measured for the Fe–Mn–Si–Cr–xN alloys. A stable modulus softening of parent was newly observed to associate with the γ→ε martensitic transformation in the alloys containing certain amount (e.g. >0.086 mass%) of nitrogen, although the rather strong softening has been always recognized to occur during its reverse transformation. The enhanced strength and the increased stacking fault energy of γ matrix by nitrogen alloying are suggested to make contribution to the soft mode.