Critical features in Cu-based shape memory strips elaborated by twin roll casting: the key role of grain size, texture and refining elements

P. LA ROCA, C. SOBRERO, R. BOLMARO, M. SADE, P. VERMAUT, P. OCHIN AND J. MALARRÍA

Osaka

Conferencia; International Conference on Martensitic Transformations (ICOMAT); 2011

Japan Institute of Metals

Rapid solidification techniques are particularly useful to obtain strips of Cu-based alloys for which shaping is difficult because of their inherent lack of ductility. The Twin Roll Casting is a rapid solidification technique that allows us to obtain in one step materials with forms (as ribbons and strips) suitable for practical applications, with reduced grain size. Due to the directional heat flow during solidification, a textured microstructure with a columnar morphology is generated. This reduces internal stresses at grain boundaries when a martensitic transformation is stress induced leading to recoverable transformation strains above 4 %. Martensitic transformation temperatures, phase stability and shape memory properties, as pseudoelasticity and thermal transformation under load, are examined in relation with the microstructures developed by this technique and specific thermal treatments. The advantages and drawbacks of the introduction of Ti and Cr as refining elements is highlighted by comparison of Cu-13Al-5Ni-1Ti and Cu-13Al-5Ni-0.3Ti-0.2Cr series with a ternary Cu-13Al-5Ni alloy.