Effect of a fourth alloying element on the microstructure and mechanical properties of Cu-Al-Ni shape memory alloys

The present investigation aims to enhance the mechanical properties and shape memory characteristics of Cu-Ni-Al shape memory alloys (SMAs) by alloying additional elements. These additions were found to control the phase morphology and grain size, along with the formation of different volume fractions, sizes, and distributions of precipitates. The features of the precipitates were mainly dependent on the type of alloying element. It was found that a Co (1.14 wt%) alloy gave the best overall improvement in terms of the transformation temperatures, ductility, and shape memory recovery. These improvements were mainly due to the exceptionally high presence of the gamma 2 phase in the microstructures of the modified alloy. The results of the current investigation were analyzed and compared to those of previous studies related to Cu-Al-Ni SMAs.