Influencing factors of martensitic transformation behavior of Ni 60Al 19Mn 16Fe 5 high-temperature shape memory alloy

Abstract

Effects of the annealed and aged processes, and thermal cycling on the martensitic transformation (MT) behavior of Ni 60Al 19Mn 16Fe 5 high-temperature shape memory alloy have been investigated by differential scanning calorimetry, X-ray diffraction, energy dispersive X-ray system, optical microscopy, and micro-hardness tester. A reversible thermoelastic MT takes place during cooling and heating in the annealed and aged Ni 60Al 19Mn 16Fe 5 alloy. The MT temperature, hysteresis and heat of the alloy increase with increasing annealed temperature. The aged processes also strongly influence the MT behavior. An excellent MT feature can be obtained from aging at 400 °C. The martensitic stabilization effect of the annealed and aged Ni 60Al 19Mn 16Fe 5 alloy is observed as an increase in the critical temperature, temperature hysteresis and the endothermic heat of the first reverse MT during thermal cycles. This stabilization effect vanishes from the second thermal cycle. The microstructure of quenched Ni 60Al 19Mn 16Fe 5 alloy consists of martensite and gamma phase. The volume fraction of gamma phase is about 20%. The hardness of martensite is higher than that of gamma phase.