| γ↔ε transformation behavior in Fe-Mn based alloys is investigated with respect to transformation temperatures, volume fraction of ε martensite and microstructure. Two Fe-Mn based alloys, an Fe-21Mn(wt%) and an Fe-32Mn-6Si(wt%) which undergo the transformation during cooling and by deformation, respectively, are used in this work. The variation in the transformation behavior is made by changing grain size for the Fe-21Mn alloy and degree of cold rolling for the Fe-32Mn-6Si alloy, respectively. The Fe-21Mn alloy consists of stacking faults in γ phase and ε martensite formed during cooling. The increase in grain size increases the volume fraction of ε martensite, however, has no influence on transformation temperatures such as Ms, As and Af. In the Fe-32Mn-6Si alloy, the volume fraction of ε martensite induced by cold rolling increases linearly with the degree of cold rolling at the early stage. The rate of the increase in the volume fraction, however, decreases with increasing degree of rolling, which is attributed to slip deformation. Transformation temperatures are increased as the degree of rolling increases. Reverse transformation in a distinctive two-step manner occurs in the specimens subjected to over 10% rolling. |
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