Evolution of the martensitic transformation by ageing in a Cu-Al-Ni shape memory alloy

Ageing phenomena in the martensitic phase beta'(1) of Cu-Al-Ni base shape memory alloys (SMAs) are rather slow; the visible outcome is a progressive evolution of the characteristics of the martensitic double left right arrow parent phase transformation. During thermal cycling, these phenomena induce only a small stabilization of the martensitic phase. However, the modification in the characteristics of the transformation on heating and cooling after ageing in the beta(1) phase are more complex. From DSC measurements, it was shown that a precipitation process occurs between 220 and 370 degreesC. When samples initially in the quenched state are cycled, several evolutions during ageing change the shape memory capability by a more or less important degradation of the thermoelastic character of the martensitic transformation.