Abstract
Effect of deformation temperature on low-cycle fatigue properties of an Fe-28Mn-6Si-5Cr shape memory alloy was investigated. Cyclic push-pull loadings at a total strain range of 0.02 were applied to the alloy at various deformation temperatures ranging from 223 to 523 K. The microstructures and fracture surfaces in the fatigue tested samples were analyzed by means of X-ray diffraction, scanning electron microscopy and electron backscattering diffraction. The highest fatigue life of 22,400 cycles was obtained at 423 K. Increasing or decreasing the deformation temperature resulted in a decrease in fatigue life to several thousand cycles. The specimens deformed to fatigue fracture at temperatures below 298 K exhibited microstructures with ε-martensite and brittle characteristics of the fracture surface, while the specimens deformed above 473 K exhibited the single γ-phase and ductile characteristics of the fracture surface. The deformation at 423 K resulted in a moderate amount of the ε-martensite and a mixed brittle/ductile fracture surface patterns. It is suggested that the highest fatigue life can be obtained when the fatigue temperature lies between Msσ and Md.
