Microstructural effect on pseudoelastic behaviour of binary Ni-Ti alloys

The effect of various heat treatments on the microstructure and pseudoelastic property of two binary Ni-Ti alloys with different Ni contents were investigated in this work. Some samples of each alloy were produced with three different heat treatments (a) solution heat treated, (b) solution heat treated and aged (c) marformed and aged. Marforming process was carried out by cold rolling some of the samples in martensitic state. The temperature dependence and reversibility of transformation induced deformation (pseudoelastic behaviour) as well as the conventional yield stress were obtained by tensile test. The formation of Ni rich precipitates (Ni4Ti3) was only observed in the alloy with higher Ni content following the ageing process. It was concluded that the microstructure produced by marforming and ageing result in the optimum pseudoelastic properties