Enhanced Physical Properties upon Sixth Element (Al) Substitution in Ni–Mn–In–Co–Cu Magnetic Shape Memory Alloys

The microstructure, martensitic transformation (MT), mechanical properties, and shape memory effect (SME) of Ni 42− x Mn 36 In 14 Co 6 Cu 2 Al x ( x = 0.3, 0.6, 0.9, 1.4) alloys are systematically examined. The results indicate that the MT temperature, hysteresis temperature, and magnetization difference intensity vary significantly with Al content changes. For x = 0.3 and x = 0.6, the MT occurred near room temperature. As the Al content increased, precipitates transitioned from being localized at grain boundaries to being dispersed throughout the entire matrix, resulting in remarkable enhancements in both compressive strength and strain. Specifically, for x = 1.4, the strength and strain improved to 2.2 times and 1.6 times relative to their original values, respectively. Furthermore, SME experiments demonstrate that an appropriate level of Al doping did not detrimentally impact SME performance. These results indicate the beneficial role of aluminum in enhancing the comprehensive properties of these alloys, meriting further investigation.