Thermostructural Shape Memory Properties of Cu-Al Base Alloy Changing by Third Cr Element Incorporations

This study presents the effects of the chromium (Cr) additions on the phase transformation behavior, thermal stability, and microstructure related to the shape memory properties of CuAlCr shape memory alloy (SMA). The influences of two different amount of Cr additions on CuAlCr SMA was investigated. The findings revealed a noticeable enhancement in the thermal and compositional stability of this SMA, attributed to the role of changing the Cr content by keeping the electron concentration (e/a ratio) of the alloy almost same (~1.52) and the role of hindered diffusion of aluminum and restricted dislocation movements due to the Cr dendrites formed between martensites. Which improved the shape memory properties and increased the characteristic transformation temperatures, enthalpy and entropy change of martensitic phase transformation. By increasing the Cr content from 5.95 at% to 10.24 at%; a maximum increase of 54 °C in As temperature and a maximum increase of 25 °C in Ms temperature were found to be occurred. Also, a maximum enthaphy change value of 16.04 J/gr and a related high entropy change value of 25.78 J/kgK were obtained. Moreover, a decrease in the reverse transformation activation energy from 416.78 kJ/mol to 48.97 kJ/mol was determined, too. The results of this research contribute to a deeper understanding of the microstructural and phase transformation dynamics in CuAlCr SMAs and highlight the potential of these materials for high-temperature Cu-based SMA applications.