Influence of Composition and Thermal History on Martensitic Transformation of Ni50Mn50xAlx (x = 17, 18, 19) Shape Memory Alloys

Abstract

The phase reactions occurring above room temperature for a series of three alloys along the line Ni50Mn50-xAlx (x = 17,18,19) have been studied. Measurements were performed by means of the four-point electrical resistometry technique complemented by differential scanning calorimetry. The martensitic transformation is identified and the strong dependence of the critical martensitic transformation temperatures as a function of composition is verified. The effect of thermal cycling is experimentally investigated and the precipitation and dissolution of equilibrium phases is discussed. Isothermal measurements are performed in order to follow the precipitation kinetics of the secondary phases. The effects of the bath-quenching temperature on the relative stability of austenite and martensite is analyzed.