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.

针对用于制备高滞后性能合金的马氏体（martensite）稳定化机制的理解，以及通过在高于奥氏体开始温度（A_s）与奥氏体结束温度（A_f）的温度下加热以恢复该马氏体对应的残余应变的可能性，是其在粘结器件中应用的核心前提。提升残余应变的可行途径之一为机械循环处理。本研究以超弹性Cu-Al-Be-Nb合金为研究对象，评估了循环次数以及富铌（Nb）颗粒析出这两种机制对残余应变提升的影响。研究结果表明，富铌析出相的存在并非残余应变提升的主导因素。此外，机械循环已被证实是提升残余应变、进而增加残留马氏体含量的有效机制。不过，残余应变的提升往往伴随塑性变形的增加。