Two-Way Shape Memory Effect Induced by Tensile Deformation in Columnar-Grained Cu(71.7)Al(18.1)Mn(10.2) Alloy

Columnar-grained Cu(71.7)Al(18.1)Mn(10.2) shape memory alloy (SMA) was prepared by a directional solidification method and exhibited a high superelasticity of 8.18% and excellent ductility at room temperature, which provided the possibility of obtaining high shape memory. However, proper pre-deformation is an essential part of repeatedly obtaining large and stable shape change. In this paper, one-time uniaxial tensile pre-deformation was carried out at the temperature range −70–−80 °C. Then, the two-way shape memory effect (TWSME) of the alloy was evaluated by the martensitic transformation strain (ε(M)) which was measured by a thermal expansion test to investigate the relationship between the pre-deformation strain (ε(T)) and the TWSME. The results showed that ε(M) of the columnar-grained Cu(71.7)Al(18.1)Mn(10.2) alloy increased at first and then decreased with the increase of ε(T). The maximum value 2.91% of the ε(M) could be reached when ε(T) was 6%. The effects of the ε(T) on transformation temperatures were also measured by differential scanning calorimetry. Based on the variations of transformation temperatures, the relationship between the internal stress induced by the pre-deformation process and the ε(M), and the influence mechanism of the pre-deformation strain on the TWSME in columnar-grained Cu(71.7)Al(18.1)Mn(10.2) alloy, were discussed. The results obtained from this work may provide reference for potential applications of Cu-based SMAs, such as self-control components, fasteners, etc.