Martensitic transformation and microstructure of rapidly solidified Ti50-xNi25Cu25Zrx shape memory alloys

Addition of Zr up to 10 at% to Ti50-xNi25Cu25Zrx alloys has been used to elaborate melt spun ribbons. It has been found that low Zr content increase the glass forming ability of the alloy with a maximum at 2.5 % where the ribbon is almost fully amorphous. Above 2.5 at% a second crystalline phase occur which prevent martensitic transformation even in thermal treated samples. After crystallization, bimodal grain size distribution in low Zr content ribbons lead to a two-stage martensitic transformation. A decrease of the transformation temperature is observed with increasing Zr content. The increase of the martensitic transformation temperatures during aging is attributed to a plate-like precipitation.