Texture Evolution of α- and β-Phases in Cold Rolled CuZnAl Shape Memory Alloy

Abstract

Adaptive textures of polycrystals are always expected in order that the direction-dependent properties of the crystal are optimally utilized. It has been an indisputable fact that textured shape memory alloys have better shape memory effects than the corresponding non-textured ones. On the other hand CuZnAl alloys usually have a tendency of being large grains in hot-rolling and a low malleability at room temperature. In this work, alternate cold-rolling and annealing in the Cu-25.95Zn-5.02Al-0.67Ti(wt%) shape memory alloy with the equi-amounts of α- and β-phases, instead of hot-rolling in the single β-phase state, refined the grain sizes and at the same time improved the cold workability because of the existence of soft α-phase. The so-formed textures in the α- and β-phases were analysed by the ODFs calculated from the pole figures measured at the surface and center of rolled sheet. The analysis results showed that the α-phase has a weak texture, two orientation tubes of which are respectively stretched out from orientation {011} to [112.45} close to {112} , and from orientation {011} to {011) . In the β-phase, only a strong α-fibre from orientation {001} through {112} to {111} was observed whose fibre axis is parallel to rolling direction and whose maximal orientation density is near {001} . In addition, comparison of the textures between the center and surface of rolled sheet indicated that the textures are as a whole homogeneous. Such a combination of two phase textures is considered to be mainly dependent upon the volume percents of both phases as well as the recrystallization annealing.