Effect of carbon on the damping capacity and mechanical properties of thermally trained Fe-Mn based high damping alloys

The effect of C on the damping and mechanical properties of thermally trained Fe-17 wt%Mn-X wt%C (0 < X < 0.06) high-damping alloys was analyzed by the impulse internal friction technique and uniaxial tensile tests. The alloys were subjected to a combination of thermo-mechanical processing and thermal cycling which resulted in a C content independent phase fraction and grain size of epsilon-martensite and gamma-austenite. The epsilon <->gamma phase transformation and the anti-ferromagnetic transition in the gamma-phase were observed in the temperature-dependent damping and modulus measurements, respectively. While C had no influence on the intrinsic internal friction of the gamma-phase, small amounts of C significantly reduced the damping associated with the motion of epsilon-gamma interface boundaries and the widening of stacking faults by the movement of partial dislocations. The C content at which these relaxation processes were suppressed, i.e. approximately 0.03 wt%C, coincided with the onset of dynamic strain aging as inferred from the appearance of serrations on the flow curves.