Superelastic cycling of Cu–Al–Ni shape memory alloy micropillars
Superelastic cycling of Cu–Al–Ni shape memory alloy micropillars
复制标题
DOI：
10.1016/j.actamat.2012.04.021
复制
发表时间：
2012-06
期刊：
影响因子：
9.4
通讯作者：
J. Juan;M. Nó;C. Schuh
中科院分区：
文献类型：
--
作者：
J. Juan;M. Nó;C. Schuh
对通过聚焦离子束从[001]取向的 Cu-Al-Ni 形状记忆合金单晶铣削的不同微柱进行超弹性纳米压缩测试。经过数百次循环，此类微柱表现出可重复的超弹性行为，在 300MPa 左右的应力和超过 5% 的应力诱导转变应变下完全恢复。循环时，引起相变的临界应力降低，相变应变增加，这都是训练效应的特征，这里根据控制马氏体板的成核、生长和恢复的微观机制来分析训练效应。机械滞后通过闭合超弹性循环期间耗散的能量来表征，并讨论了其在循环期间的演变。还发现微柱的超弹性循环取决于应变率。这里研究的最高应变率 10−1s−1，被发现会影响 γ3' 和 β3' 马氏体的成核和生长动力学，从而减少机械滞后和相变应变。最后，在增加最大载荷下进行了特定的循环测试，以分析微柱塑性变形的极限，该变形发生在 500 至 700MPa 之间。
Superelastic nanocompression tests are performed on different micropillars milled by focused ion beam from [001]-oriented single crystals of Cu–Al–Ni shape memory alloys. Over hundreds of cycles such micropillars exhibit reproducible superelastic behavior with complete recovery at stresses around 300MPa and stress-induced transformation strains above 5%. Upon cycling, the critical stress to induce the transformation decreases, and the transformation strain increases, both signatures of a training effect which is analyzed here in terms of the microscopic mechanisms controlling the nucleation, growth and recovery of the martensite plates. The mechanical hysteresis is characterized through the energy dissipated during closed superelastic cycles, and its evolution during cycling is discussed. The superelastic cycling of the micropillars is also found to depend on the strain rate. The highest strain rate studied here, 10−1s−1, is found to impinge upon the nucleation and growth kinetics of γ3′and β3′martensites, with the result that the mechanical hysteresis and transformation strain are reduced. Finally, specific cycling tests have been conducted at increasing maximum loads to analyze the limit for plastic deformation of the micropillar, which happens between 500 and 700MPa.