Analysis of dissipation of a burst-type martensite transformation in a Fe-Mn alloy by internal friction measurements

Abstract

Recently, we have proposed a theory to analyze the first-order phase transition (FOPT) in solids. In order to test the concept of the physics of dissipation during FOPT in solids, it is necessary to test the theory with different FOPT system. We study here a burst-type martensite transformation in a Fe-18.8% Mn alloy sample for this purpose. We investigate the characteristics of γ(fcc)⇌ɛ(hcp) transformation in this alloy and measure the dependence of internal friction (IF) during γ/ɛ transformation in varying rate of temperature Ṫ and vibration frequency ω. For free oscillations, the IF was defined to be Qδ-1=δ/π where δ is the logarithmic decrement. For general (forced) oscillations, IF is usually defined to be Qw-1=(1/2π)(ΔW/W), where ΔW is the dissipation over one cycle, while W is the maximum stored energy. During our analysis, the relation between Qδ-1 and Qw-1 is deduced. The parameter l (coupling factor between phase interface and oscillating stress) takes a small value (0.015–0.035) during PT, but takes a large value (0.86) during static state. The parameter n (exponent of rate for effective PT driving force) takes a large value 0.33 during heating and 0.47 during cooling. The physical meaning of n and l is discussed. The methodology introduced here appears to be an effective way of studying FOPT in solids. © 1996 The American Physical Society.