Structural change due to martensite aging of CuZnAlMnNi shape memory alloy

The microstructures of a CuZnAlMnNi shape memory alloy after one year aging in martensite phase were investigated by transmission electron microscopy. It was found that the substructure of stacking faults in the original martensite plates becomes indistinct, and the amount decreases. However, the equilibrium face centered cubic (fcc) α-phase can be observed forming at martensite plate boundaries or inside the plates. The structural variation during aging is responsible for the degradation of shape memory property and transformation temperatures when Cu-based SMA actuators are in use.