Fe-Mn-Si-Cr-Ni composite powders are utilized to form a functional shape memory alloy cladding layer (SMACL) using a laser cladding method. The microstructure, microhardness, and phase composition of the SMACL are measured, and the extent of deformation of the laser cladding samples is determined. The SMACL is composed of planar, cellular, and dendritic crystals, equiaxed grains, and oxides with increasing distance from the substrate surface. The SMACL is further composed of ε-martensite and γ-austenite phases, while the tempered SMACL consists mainly of γ-austenite. Extensive deformation occurs in AISI 304 stainless steel laser cladding samples. By contrast, limited deformation is observed in the SMACL samples.
The paper presents the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy, namely the alloy causes positive/reverse ε martensitic transformation and accompanied by deformation in order to adapt the variation of the outside macroscopical stress and deformation. From XRD analysis, it is found that the stress-induced γ↔ε martensitic transformation and its reverse transformation would occur in Fe-Mn-Si shape memory alloy under the tension-compression stress and also validated the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy. In cycles of tension and compression deformation, the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy can increase fatigue life of the alloy by reducing stress concentration, restraining plastics gliding deformation and delaying the formation and growing of microcracks. The fatigue fracture in Fe-Mn-Si alloy shows quasi-cleavage brittle rupture type.
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