Atomistic characterization of pseudoelasticity and shape memory in NiTi nanopillars
Atomistic characterization of pseudoelasticity and shape memory in NiTi nanopillars
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DOI：
10.1016/j.actamat.2012.08.004
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发表时间：
2012-10
期刊：
影响因子：
9.4
通讯作者：
Y. Zhong;K. Gall;T. Zhu
中科院分区：
文献类型：
--
作者：
Y. Zhong;K. Gall;T. Zhu
采用分子动力学模拟方法研究了镍钛纳米结构的伪弹性和形状记忆效应的原子机制。对于经受压缩加载-卸载的取向纳米柱，我们观察到伪弹性或形状记忆响应，这取决于控制相变和变形孪生可逆性的施加应变和温度。我们发现，由于位错钉扎的孪晶边界的不可逆的孪晶，而分级孪晶组织促进可逆的孪晶。纳米尺寸效应表现为应力-应变曲线中的载荷锯齿、应力平台和大的滞后回线，这是由驱动纳米尺寸体积中的成核控制相变和变形孪晶所需的高应力引起的。我们的研究结果强调了原子解析建模的重要性，了解的相位和变形可逆性，决定纳米结构的形状记忆合金的伪弹性和形状记忆行为。
Molecular dynamics simulations are performed to study the atomistic mechanisms governing the pseudoelasticity and shape memory in nickel–titanium (NiTi) nanostructures. For a 〈110〉 – oriented nanopillar subjected to compressive loading–unloading, we observe either a pseudoelastic or shape memory response, depending on the applied strain and temperature that control the reversibility of phase transformation and deformation twinning. We show that irreversible twinning arises owing to the dislocation pinning of twin boundaries, while hierarchically twinned microstructures facilitate the reversible twinning. The nanoscale size effects are manifested as the load serration, stress plateau and large hysteresis loop in stress–strain curves that result from the high stresses required to drive the nucleation-controlled phase transformation and deformation twinning in nanosized volumes. Our results underscore the importance of atomistically resolved modeling for understanding the phase and deformation reversibilities that dictate the pseudoelasticity and shape memory behavior in nanostructured shape memory alloys.