The effect of grain size on the damping capacity of Fe-17Â wt%Mn

The grain size dependence of the damping capacity of Fe-17 wt%Mn steel was investigated. A high damping capacity was measured in the ultra-fine grained steel, despite its lower volume fraction of ε martensite and lower density of ε variant boundaries and ε/γ phase boundaries. Dilatometry of the ultra-fine grained Fe-17 wt%Mn steel revealed that the ε↔γ phase transformation was largely suppressed. The features of the damping spectra were related to the anti-ferromagnetic transition in the γ phase, the thermo-elastic ε↔γ phase transformation and the motion of grain boundaries in the ultra-fine grained microstructure. The damping spectrum of the ultra-fine grained Fe-17 wt%Mn steel was dominated by grain boundary damping effects.