Microstructure change and shape memory characteristics in welded Fe–28Mn–6Si–5Cr–0.53Nb–0.06C alloy

In the present study, an Fe–28Mn–6Si–5Cr–0.53Nb–0.06C (mass%) alloy was employed to investigate the influence of laser beam welding (LBW), electron beam welding (EBW) and tungsten-insert gas welding (TIGW) on shape memory properties. This alloy was recently found to exhibit very good shape memory effect with simple thermomechanical treatments without so-called the ‘training’. After homogenizing heating at 1470 K for 10 h, two different treatments were performed: (a) 14% rolled at 870 K followed by aging at 1070 K for 10 min and then welded, (b) first welded and then extended 10% at room temperature, followed by aging at 1070 K for 10 min. The results show that the shape recovery of the alloy was slightly different depending on welding method. The shape recoveries for the samples treated in (a) by LBW, EBW and TIGW were 90%, 87%, 81% and those for the samples treated in (b) were 86%, 84% and 79%, respectively. After welding, the alloy still possesses very high shape recovery stress of about 250 MPa for the samples treated in (a). High strength of the weld zone is due to the dendrite structure with very fine columnar grains. All of these results on welding will make a wide industry application of the Fe–Mn–Si based SMAs in the near future.