Internal friction observation of the ε ⇆ γ transformation in a Fe-Mn alloy

The internal friction behavior of a quenched Fe-22 wt.% Mn alloy was investigated in the temperature range from room temperature to 260 degrees C using a multifunctional internal friction apparatus. It has been shown that an internal friction peak appears at about 215 degrees C (named as PH) on the heating curves and dynamic modulus has a minimum corresponding to the peak temperature. The PH peak does not appear at the temperature during subsequent in situ cooling and another internal friction peak presents at about 45 degrees C (named as P-L) on the cooling curve. The PH peak temperature does not vary with vibration frequency, and thereby the peak has no relaxational features. Its height increases with decreasing vibration frequency and increasing heating rate, and there is a linear relationship of the peak height and T/f. It can be suggested that the PH peak during heating results from epsilon <-> gamma transformation and the P-L peak during cooling corresponds to gamma <-> epsilon transformation for the quenched Fe-22 wt. %Mn alloy. (c) 2006 Elsevier B.V. All rights reserved.