Tailoring the Microstructure in Polycrystalline Co-Ni-Ga High-Temperature Shape Memory Alloys by Hot Extrusion
|authors:||E. Karsten, G. Gerstein, O. Golovko, A. Dalinger, C. Lauhoff, P. Krooss, T. Niendorf, A, Samsonenko, H.J. Maier|
|publication:||Shape Memory and Superelasticity|
Co–Ni–Ga alloys represent a new class of promising high-temperature shape memory alloys allowing realization of functional components for applications at elevated temperatures. Single crystals show a fully reversible pseudoelastic response at temperatures up to 500 C. However, for most industrial applications, the application of polycrystalline material is needed. Polycrystalline Co–Ni–Ga alloys suffer from the anisotropic properties inherent to shape memory alloys, i.e., a strong orientation dependence of transformation strains, and therefore, are prone to intergranular fracture. This drawback can be curtailed by using appropriately textured material with a favorable grain-boundary orientation distribution. The current study discusses the impact of a hot-extrusion process on microstructural evolution and functional properties of polycrystalline Co–Ni–Ga high-temperature shape memory alloys paving the way to their robust application.