The microstructure of melt spun Ti–Ni–Cu–Zr shape memory alloys

NiTi base shape memory melt spun ribbons with a high substitution of Ni by Cu and Ti by Zr have been analysed. Depending of the chemical composition of the alloy, the ribbons are crystalline or amorphous. Transmission electron microscopy (TEM) studies in the as-cast state and after crystallization indicated that in the as-cast state the Ti40Ni25Cu25Zr10 ribbons are constituted of two phases (Ti2Ni+amorphous phase) whereas the Ti40Ni35Cu15Zr10 ribbons are fully amorphous and are single phase after crystallisation with a B2 structure. High resolution electron microscopy (HREM) observations have shown that the crystalline/amorphous phase interface is highly wavy even at the nanometric scale and that the B2 particles are single ordered domains.