Lim Hojun, Carroll Jay D, Battaile Corbett C, Chen Shuh Rong, Moore Alexander P, Lane J Matthew D
Department of Computational Materials and Data Science, Sandia National Laboratories, Albuquerque, New Mexico, 87175, USA.
Department of Materials Mechanics and Tribology, Sandia National Laboratories, Albuquerque, New Mexico, 87175, USA.
Sci Rep. 2018 Apr 3;8(1):5540. doi: 10.1038/s41598-018-23879-1.
Deformation mechanisms in bcc metals, especially in dynamic regimes, show unusual complexity, which complicates their use in high-reliability applications. Here, we employ novel, high-velocity cylinder impact experiments to explore plastic anisotropy in single crystal specimens under high-rate loading. The bcc tantalum single crystals exhibit unusually high deformation localization and strong plastic anisotropy when compared to polycrystalline samples. Several impact orientations - [100], [110], [111] and [[Formula: see text]] - are characterized over a range of impact velocities to examine orientation-dependent mechanical behavior versus strain rate. Moreover, the anisotropy and localized plastic strain seen in the recovered cylinders exhibit strong axial symmetries which differed according to lattice orientation. Two-, three-, and four-fold symmetries are observed. We propose a simple crystallographic argument, based on the Schmid law, to understand the observed symmetries. These tests are the first to explore the role of single-crystal orientation in Taylor impact tests and they clearly demonstrate the importance of crystallography in high strain rate and temperature deformation regimes. These results provide critical data to allow dramatically improved high-rate crystal plasticity models and will spur renewed interest in the role of crystallography to deformation in dynamics regimes.
体心立方金属的变形机制，尤其是在动态条件下，呈现出异常的复杂性，这使得它们在高可靠性应用中的使用变得复杂。在此，我们采用新颖的高速圆柱冲击实验，以探究单晶试样在高速加载下的塑性各向异性。与多晶样品相比，体心立方钽单晶表现出异常高的变形局部化和强烈的塑性各向异性。在一系列冲击速度范围内，对几个冲击取向——[100]、[110]、[111]和[[公式：见原文]]——进行了表征，以研究与取向相关的力学行为与应变率的关系。此外，在回收圆柱中观察到的各向异性和局部塑性应变表现出强烈的轴对称性，且根据晶格取向而有所不同。观察到二倍、三倍和四倍对称性。我们基于施密德定律提出一个简单的晶体学观点，以理解所观察到的对称性。这些测试首次探究了单晶取向在泰勒冲击试验中的作用，并且清楚地证明了晶体学在高应变率和温度变形条件下的重要性。这些结果提供了关键数据，以显著改进高速晶体塑性模型，并将激发人们对晶体学在动态条件下对变形作用的新兴趣。
