Influence of Mechanical Cycling on Residual Strain in Superelastic Cu-Al-Be-Nb Alloys

The understanding of the stabilization mechanism of martensite used to obtain alloys with high hysteresis and the possibility of recovering this martensite (residual strain) by heating at temperatures higher than As and Af have been fundamental for application in bonding devices. One of the possibilities to enhance residual strain is through mechanical cycling. This work evaluated the influence of number of cycles and the effect of precipitation of Nb-rich particles as mechanisms to increase residual strain in superelastic Cu-Al-Be-Nb alloys. The results showed that the presence of Nb-rich precipitates was not a predominant factor for the enhancement of residual strain. In addition, mechanical cycling has proved to be an efficient mechanism for raising residual strain, and consequently increasing the amount of martensite retained. However, the gain of residual strain is accompanied by an increase of plastic deformation.