Phase Stability of Three Fe–Mn–Al–Ni Superelastic Alloys with Different Al: Ni Ratios

Abstract

Fe–Mn–Al–Ni superelastic alloy is a potential candidate for diverse engineering applications due to its outstanding properties and low material costs. Recent studies suggest that slight changes in the chemical composition severely affect superelastic response, phase stability and grain growth kinetics. In this paper, we found that the Al stabilizes the parent α phase at high temperature and promotes the formation of β precipitation at lower temperature. An alloy with a 3:1 ratio between Al and Ni produces homogeneously distributed β precipitates with high phase fraction in the alpha matrix after quenching from 1200 °C. The presence of these precipitates stabilizes the α phase, lowers the martensitic transformation temperature and gives the alloy a fully-reversible stress-induced martensitic transformation behaviour without the need to apply an aging step. In alloys with lower Al content the β precipitation produced during quenching is severely restricted and pseudoelasticity is impaired.