Effect of chromium element on transformation, mechanical and corrosion behavior of thermomechanically induced Cu-Al-Ni shape-memory alloys

Cu-Al-Ni shape-memory alloys are considered as high potential materials for high-temperature applications. The aim of this research was to evaluate the increasing strain value and Cr addition on martensite morphology, transformation temperatures, mechanical, and corrosion properties of Cu-Al-Ni alloy. To this purpose, thermomechanical treatment which includes successive hot rolling, annealing, and hydraulic pressing passes was applied. In addition, tensile test, differential scanning calorimetry, and potentiodynamic polarization were carried out to compare the properties of prepared samples. The results showed that by increasing the applied strain, morphological transition from wide laths to acicular martensite with monoclinic structure was occurred. The chromium element acts as a grain refiner in this alloy by restricting the grain growth. This element leads to microstructural embrittlement, diminishing the mechanical properties. Besides, the influence of applied strain and Cr content on corrosion resistance of Cu-Al-Ni alloy was reciprocal. Despite suitable effect of Cr on corrosion behavior, increasing the applied strain facilitated the corrosion rate. Another subtle point is that both Cr addition and higher strain value reduce austenite to martensite transformation temperatures and hysteresis temperature interval.