Microstructure, texture and shape memory effect in Ni25Ti50Cu25 ribbons and strips

A ribbon and strip of Ni25Ti50Cu25 shape memory alloy were produced by melt-spinning and twin roll casting technique, respectively. It results in different orientation of grains across a ribbon and strip forming fibre and sheet textural components. The as-cast strip shows higher volume fraction of the grains oriented along martensitic “friendly” direction 〈0 1 1〉 than the ribbon. Additionally, in aim to grains reorientation the ribbon was annealed at various temperatures with constant time. Annealing results in developing of the 〈0 0 1〉 fibre texture and two sheet component: {0 0 1}〈1 0 0〉 and {0 0 1}〈1 1 0〉. However, annealing at too high temperature (773 K) caused precipitation, which leaded to decrease of the degree of shape recovery. Generally, the presence of the component {0 0 1}〈1 1 0〉 improves shape recovery measured by the change of elongation versus temperature under constant load.