Abstract The mechanistic origin of fatigue in Shape Memory Alloys (SMAs) is addressed using atomistic simulations. A causal explanation is proposed for the known agreement between the fatigue-activated slip system and the martensitic twinning system. As a model system, the Type II twin boundary (TB) in NiTi B19′ martensite phase is analyzed. TEM-based models have established the presence of disconnections on the TB. Topological models establish the TB migration to depend on the motion of twinning partials on these disconnections. A disconnection is setup within a Molecular Statics (MS) framework. A twinning partial is positioned on it by enforcing continuum displacement fields external to a prescribed core of atoms which is subsequently relaxed under governance of the interatomic potential. The displacement fields are calculated from the anisotropic Eshelby-Stroh formalism and enforced in a non-Cauchy-Born adherent manner to obtain the right core structulre. TB migration is simulated as a motion of this disconnection under applied load. In the presence of a barrier to this motion, a dislocation reaction occurs where a stacking fault emits at the TB while returning a residual negated partial. The emissary fault partial is proposed as a precursor to the resulting slip observed in reverse-transformed austenite.

中文翻译：

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马氏体孪晶边界迁移作为形状记忆合金中不可逆滑移的来源

摘要 使用原子模拟解决了形状记忆合金 (SMA) 疲劳的机械起源。对疲劳激活滑移系统和马氏体孪生系统之间的已知一致性提出了因果解释。作为模型系统，分析了 NiTi B19' 马氏体相中的 II 型孪晶界 (TB)。基于 TEM 的模型已经确定了 TB 上断开连接的存在。拓扑模型建立了 TB 迁移以依赖于这些断开上的孪生部分的运动。断开连接是在分子静力学 (MS) 框架内设置的。通过在规定的原子核心外部强制执行连续位移场，将孪生部分定位在其上，随后在原子间势的控制下放松。位移场是根据各向异性 Eshelby-Stroh 形式主义计算的，并以非柯西出生粘附方式强制执行以获得正确的核心结构。TB 迁移被模拟为在施加负载下这种断开的运动。在此运动存在障碍的情况下，会发生位错反应，其中在 TB 处发出堆垛层错，同时返回残留的否定部分。发射断层部分被认为是在逆转变奥氏体中观察到的滑移的前兆。位错反应发生在堆垛层错在 TB 处发射，同时返回残留的否定部分。发射断层部分被认为是在逆转变奥氏体中观察到的结果滑移的前兆。位错反应发生在堆垛层错在 TB 处发射，同时返回残留的否定部分。发射断层部分被认为是在逆转变奥氏体中观察到的结果滑移的前兆。