Effect of Mn Element on the Microstructure, Thermal Stability, and Strain Recovery Characteristics of Cu–12.0Al–4.0Ni Alloy

This paper presents a comprehensive investigation into the influence of manganese on the microstructural characteristics and properties of Cu–12.0Al–4.0Ni–xMn high-temperature shape memory alloys. The study reveals that the matrix structure of these alloys is primarily composed of both 18R and 2H martensitic phases, with a notable increase in the proportion of the 18R phase as the Mn content rises. Notably, the addition of Mn significantly enhances the thermal stability of the Cu–12.0Al–4.0Ni alloy system. Upon examining the alloys with varying Mn contents, it is observed that when the Mn content is less than 1.5 wt%, the phase transformation temperatures exhibit considerable fluctuations during thermal cycling. In contrast, when the Mn content reaches or exceeds 1.5 wt%, the Cu–12.0Al–4.0Ni–xMn alloy demonstrates commendable thermal stability even after 50 thermal cycles. Furthermore, among the studied compositions, the Cu–12.0Al–4.0Ni–1.5Mn alloy exhibits optimal plasticity of 12.8% and shape memory effect of 6.4%.