Effects of strain amplitude and temperature on the damping capacity of an Fe-19Mn alloy with different microstructures

The influences of strain amplitude (10−5–10−4) and temperature (25°C–500°C) on the internal friction of a cold-drawn and solution treated Fe-19Mn alloy were investigated. The internal friction was measured using reversal torsion pendulum and multifunction internal friction equipment. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of the solution treated alloy was related to strain amplitude, which could be explained using the movement of Shockley partial dislocations (bowing out and breaking away). But the internal friction of the cold-drawn alloy was independent of strain amplitude because of high density dislocations formed by cold forming. Moreover, when the temperature was changed between 25°C and 500°C, the internal friction of the cold-drawn alloy increased slowly from 25°C to 375°C, and then increased quickly from 375°C to 500°C. However, for the solution treated alloy, there was an internal friction peak at about 210°C in the heating process (from 25°C to 500°C), and there was another internal friction peak at about 150°C in the cooling process. These peaks could be explained using the heat-assisted movement of dislocations.