Effects of alloying quantities in the production of Cu-based shape memory metals on the phase transformation temperatures and characterization

Copper-based shape memory alloys which are an alternative for NiTi shape memory metals which is quite costly material, have been getting advanced day by day. Copper-based shape memory alloys are used as generally Cu-Al binary alloy. However, in order to get phase stability and improve the physical properties, Zn, Ni, Be and Mn elements are used as a ternary alloying element. In the production of shape memory alloys a small variation on production condition or heat treatment conditions leads to change, transformation temperature, affects the crystal structure the morphology and mechanical properties substantially. In this study, Mn was used as a third alloying element since it provides more advantageous qualities to alloy and aimed to investigate on effects of alloying quantities in the production on transformation temperatures. The experiments were performed in two stages. The first stage experiments were conducted for selecting parameters of aging temperature and duration of CuAlMn alloys which were produced in arc furnace at argon environment. The obtained ideal aging parameters were used in the aging process of after homogenisation of the produced the samples which are the second stage named as characterization of the transformation temperature experimental group. After heat treatment process of the samples produced by the above methods, martensite phase transformation temperatures were determined by differential scanning calorimeter device. Then the samples plane reflection, which is used for determining the crystal structures, has been anaylzed by X-ray powder diffractometer. In order to obtain the surface morphology of the samples, scanning electron microscope were used. Each value of the obtained transformation temperautures such as martensite start, martensite finish, austenite start and austenite finish temperatures variations graphs were generated according shifts of the elements of alloys. The effects of the chemical ratio of alloying elements to transformation temperature were examined through these graphs.