Under high pressures, phase transition, as well as deformation twins, are constantly reported in many BCC metals, whose interactions are of fundamental importance to understand strengthen mechanism of these metals under extreme conditions. However, the interactions between twins and phase transition in BCC metals are remain largely unexplored. In this work, interactions between coherent twin boundaries and $α\to ε$ phase transition of iron are investigated using both non- equilibrium molecular dynamics simulations and nudge elastic band method. Mechanisms of both twin-assisted phase transition and reverse phase transition are studied and orientation relationships between BCC and HCP phase are found to be <11-1>BCC || <-12-10>HCP and <1-10>BCC || <0001>HCP for both cases. The twin boundary corresponds to after the phase transition. It is amazing that the reverse transition seems to be able to "memory" and recover the initial BCC twins. The memory would partly loss when plastic slips take place in the HCP phase before the reverse transition. In the recovered initial BCC twins, three major twin spacing are observed, which are well explained in terms of energy barriers of the transition from HCP phase to BCC twin. Besides, variant selection rule of the twin assisted phase transition is also discussed. The results of present work could be expected to give some clues for producing ultra-fine grain structure in materials exhibiting martensitic phase transition.
Transformation-mediated twinning governs plasticity in body-centered cubic nanocrystals under extreme loading
University of West Bohemia in Pilsen（西波希米亚大学）；University of Helsinki（赫尔辛基大学）；National Centre for Nuclear Research（国家核研究中心）；Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）
Deformation behavior of Mg-8.5wt.%Al alloy under reverse loading investigated by in-situ neutron diffraction and elastic viscoplastic self-consistent modeling
Suppression of acoustic emission during superelastic tensile cycling of polycrystalline Ni$_{50.4}$Ti$_{49.6}$
研究了超弹性/弹热合金Ni $_{50.4}$ Ti $_{49.6}$（at. %）使用拉伸应变驱动。我们使用两个独立的AE传感器，以定位AE事件，并专注于从机械试验机的夹具中产生的AE的贡献。在第一次机械加载期间存在显著的AE活动，这主要是由于在正向马氏体转变期间宽Lüders样带的成核和生长（使用可见光和红外（IR）辐射成像）导致晶间相互作用的持续变化。AE活动被抑制在随后的反向马氏体相变卸载，并在连续的加载/卸载循环，Lüders样带变窄，修改晶粒间的相互作用，以更小的程度。在第一次加载后，我们发现与马氏体相变相关的AE活动很弱，我们认为这是因为Ni-Ti中的弹性各向异性和应变不相容性较低。我们还发现，AE活动变得较弱的机械循环，由于保留马氏体的增加。
Thermodynamically-consistent derivation and computation of twinning and fracture in brittle materials by means of phase-field approaches in the finite element method
Discrete Dislocation Dynamics Modeling of Nanotwinned Materials: Orientation Effects in a Multilayer Twinned Structure of Copper
Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, School of Mechanics and Aeronautics（四川省力学与结构安全重点实验室，力学与航空学院）；Department of Materials Science and Engineering, Institute of Materials Simulation WW8, Friedrich-Alexander University of Erlangen-Nuremberg（埃尔朗根-纽伦堡大学材料工程系，材料模拟研究所WW8）；Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所）
Fifth-degree elastic potential for predictive stress-strain relations and elastic instabilities under large strain and complex loading in Si
在复杂载荷下的材料产生大的应变，并且通常通过弹性不稳定性转变，如在简单和复杂系统中所观察到的。在这里，我们提出了硅我在大应变的拉格朗日应变方面的$5^{th}$阶弹性势通过最小化误差相对于密度泛函理论（DFT）的结果。任意复杂载荷下的Cauchy应力-Lagrangian应变曲线与密度泛函理论（DFT）结果吻合良好，包括驱动Si I $\rightarrow$ II相变（PT）的弹性不稳定性和剪切不稳定性。PT条件下的Si I $\rightarrow$ II的作用下的立方轴向应力是线性的柯西应力与DFT预测。这样的弹性势允许研究弹性不稳定性和取向依赖性，导致不同的PT，滑移，孪生，或断裂，提供了一个基本的基础，连续模拟极端负载下的晶体行为。
Revealing the dynamic responses of Pb under shock loading based on DFT-accuracy machine learning potential
Institute of Applied Physics and Computational Mathematics（应用物理与计算数学研究所）；Graduate School of China Academy of Engineering Physics（中国工程物理研究院研究生院）；National Key Laboratory of Computational Physics, Institute of Applied Physics（计算物理国家重点实验室，应用物理研究所）；HEDPS, CAPT, College of Engineering（HEDPS、CAPT、工程学院）；School of Physics, Peking University（北京大学物理学院）
