STRUCTURAL CHANGES IN Co-BASED F-SMA

摘要

The Co_(38)Ni_(33)Al_(29) alloy as a potential ferromagnetic shape memory alloy was investigated. The method of preparation of the unidirectional solidified single-crystals from cast material is described. The high-temperature annealing and subsequent quenching was found to be necessary condition for martensitic transformation and the shape memory behavior. The martensitic transformation temperatures of annealed samples were about 200 K, while as-cast sample did not exhibit any sharp transformation. The transformation temperatures were determined from magnetic measurement. All martensitic structures observed locally by microscopic methods at room temperature are thus stress induced. These results agree with pseudoelastic behavior observed in annealed and quenched samples.