Bending-fatigue performance of the dissimilar joints of Fe-Mn-Si memory alloy and 304 stainless steel

Abstract

The dissimilar joints of Fe-17Mn-5Si-10Cr-5Ni memory alloy and 304 stainless steel were welded by 5 kw transverse flow CO2 laser. The fracture morphology, microhardness of the welding joint was analyzed by field emission scanning electron microscopy, micro hardness tester, and bending fatigue test. The results showed that the fracture location of dissimilar joint is in the welding joint, and the fusion zone to weld areas prone to stress concentration while the formation of cracks. The full cyclic fatigue fracture of dissimilar joints consisted of the extension zone and instantaneous fracture zone. In the former, there were fatigue striations, dissociation steps and some arc tearing ridges, showing typical quasi-cleavage brittle fracture characteristics, and in the latter, there were a lot of dimples, showing plastic fracture characteristics. The toughness of dissimilar joint is better than that of the 304 stainless steel joint.