Singh Saransh, Gorman Martin G, Heighway Patrick G, Bernier Joel V, McGonegle David, Lee Hae Ja, Nagler Bob, Eggert Jon H, Smith Raymond F
<a href="https://ror.org/041nk4h53">Lawrence Livermore National Laboratory</a>, Livermore, California, USA.
Department of Physics, <a href="https://ror.org/052gg0110">Clarendon Laboratory</a>, University of Oxford, Oxford, United Kingdom.
Phys Rev Lett. 2024 Aug 30;133(9):096101. doi: 10.1103/PhysRevLett.133.096101.
The response of materials under dynamic compression involves a complex interplay of various deformation mechanisms aimed at relieving shear stresses, yielding a remarkable diversity in material behavior. In this Letter, we utilize femtosecond x-ray diffraction coupled with nanosecond laser compression to reveal an intricate competition between multiple shear-relieving mechanisms within an elemental metal. Our observations in shocked-compressed single-crystal Zr indicate a disorder-mediated shear relaxation at lower pressures. Above the phase-transition pressure, we observe the increasing contribution of structural phase transition in relieving shear stress. We detect not one but three concurrent pathways during the transition from the hcp to a hex-3 structure. These complex dynamics are partially corroborated through multimillion-atom molecular dynamics simulations employing a machine-learned interatomic potential. Our observation of multiple concurrent pathways and disorder during shock compression underscore the far greater intricacies in the dynamic response of metals than previously assumed.
材料在动态压缩下的响应涉及各种变形机制之间复杂的相互作用，旨在缓解剪切应力，从而使材料行为呈现出显著的多样性。在本信函中，我们利用飞秒X射线衍射与纳秒激光压缩相结合的方法，揭示了一种元素金属内部多种剪切缓解机制之间的复杂竞争。我们对冲击压缩单晶Zr的观察表明，在较低压力下存在无序介导的剪切弛豫。在相变压力以上，我们观察到结构相变在缓解剪切应力方面的贡献不断增加。在从hcp结构转变为hex-3结构的过程中，我们检测到并非一条而是三条同时存在的路径。通过采用机器学习原子间势的数百万原子分子动力学模拟，这些复杂的动力学过程得到了部分证实。我们对冲击压缩过程中多条同时存在的路径和无序现象的观察强调，金属动态响应中的复杂程度远比之前设想的要高得多。
