Gefügeänderungen in Cu-Al-Ni-Formgedächtnislegierungen / Microstructural Changes in Cu-Al-Ni Shape Memory Alloys

Abstract

Microstructures of strong varying grain sizes have been established in wire specimens of a high-temperature CuAlNi shape memory alloy by applying different betatizing heat treatments. In samples suitable for thermomechanical treatment an intrinsic two-way shape memory effect was induced. In the coarse grained samples the development of the reversible strain during training occurs at far smaller external forces compared to the fine grained specimens. While in the microstructure of the untrained samples several martensite variants can be observed per grain, in the trained condition mostly one variant is dominating and the structure is considerably finer. Annealing at appropriate temperatures after betatizing treatment resulted in a positive effect on the magnitude of the obtained two-way shape memory effect.