TRAINING EFFECTS ON DAMPING CAPACITY IN Fe-Mn AND Fe-Mn-Cr ALLOYS

Training effect in the Fe-Mn-Si shape memory alloy is known as useful method to improve the shape memory effect. In this study, the training effects on damping capacity in Fe-20mass%Mn and Fe-20.5mass%Mn-12.5mass%Cr alloys have been investigated. As training treatments, the thermal training (only thermal cycling) and the thermo-mechanical training (thermal cycling with rolling deformation) are carried out. Internal friction was measured at room temperature using a free-decay method. Moreover, the behavior of dislocations was observed by TEM. Both training treatments improve the damping capacity of the Fe-Mn alloys with increasing the number of treatment. Strong training effect was found for the specimens trained by the thermo-mechanical training. The main training effect by thermal cycles is concluded to be due to size effects, while the size effects and volume fractional effects of epsilon-martensite phase affect the damping capacity of the thermo-mechanically trained alloys. These training methods can improve both damping capacity and strength of Fe-Mn alloys.