Studies on the effect of grain refinement and thermal processing on shape memorycharacteristics of Cu–Al–Ni alloys

Abstract

Though Ni–Ti shape memory alloys are used extensively in a variety of engineering andmedical applications because of their attractive shape memory characteristics, they stillsuffer from certain drawbacks, such as low transformation temperatures, difficulty inproduction and processing and high cost of raw materials. Copper-based alloys have,therefore, come as an alternative to Ni–Ti shape memory alloys. They are easier to produceand process and are also less expensive. They are used where Ni–Ti alloys cannot be used.But Cu–Al–Ni shape memory alloys also pose problems since they are brittle and possesslower shape recovery strains and stresses. With a view to increasing the shapememory characteristics and ductility of Cu–Al–Ni shape memory alloys, they weresubjected to grain refinement and thermomechanical processing. The presentstudy establishes that grain-refining additions result in considerable reductionin the grain size of the alloys. In addition, grain refinement and alloying causean increase in the transformation temperatures. The results are analysed in thelight of the explanations/theories put forth in recent papers related to Cu–Al–Nishape memory alloys, and an attempt has been made to compare the results.