THE MECHANISM OF THERMOMECHANICAL TRAINING OF A NEWLY DEVELOPED FE-MN-SI-CR-CU SHAPE-MEMORY ALLOY

Thermomechanical training was carried out on a newly developed Fe-20Mn -6Si-7Cr-1Cu shape memory alloy. It was observed that the effectivene: ss of thermomechanical training largely depends on the recovery anneal ing temperature and the pre-strain during training. Based on the analy sis of the changes in critical stress for martensite formation, the cr itical stress for (lip deformation, the phase transformation temperatu res and microstructural development during training, it was concluded that the mechanism of thermomechanical training is based on the follow ing two factors: (1) lowering of the critical stress for martensite fo rmation, making stress induced gamma-->epsilon transformation easier; and (2) decreasing the Af temperature and refining the epsilon martens ite structure, thus reducing the energy barrier for the epsilon-gamma reverse transformation. The optimum thermomechanical training conditio ns have been determined for the alloy studied.