Lee Hyunsoo, Shabani Mitra, Pataky Garrett J, Abdeljawad Fadi
Department of Mechanical Engineering, Clemson University, Clemson, SC, 29634, USA.
Department of Materials Science and Engineering, Clemson University, Clemson, SC, 29634, USA.
Sci Rep. 2021 Jan 11;11(1):428. doi: 10.1038/s41598-020-77487-z.
High entropy alloys (HEA) are a class of materials that consist of multiple elemental species in similar concentrations. The use of elements in far from dilute concentrations introduces a multi-dimensional composition design space by which the properties of metallic systems can be tailored. While the mechanical behavior of HEAs has been the subject of active research recently, the role of grain boundaries (GBs) in their deformation behavior remains poorly understood. Motivated by recent experiments on HEAs demonstrating that GBs act as nucleation sites for deformation twins, herein, we leverage atomistic simulations to construct a series of equiatomic CoCrFeMnNi HEA bicrystals with [Formula: see text] and [Formula: see text] symmetric twist GBs and examine their tensile behavior and underlying deformation mechanisms at 77 K. Simulation results reveal that plastic deformation proceeds by the nucleation of partial dislocations from GBs, which then grow with further loading by bowing into the bulk crystals leaving behind stacking faults. Variations in the nucleation stress exist as function of GB character, defined in this work by the twist angle. Our results provide future avenues to explore GBs as a microstructure design tool to develop HEAs with tailored properties.
高熵合金（HEA）是一类由多种元素以相似浓度组成的材料。使用远非稀释浓度的元素引入了一个多维成分设计空间，通过该空间可以调整金属系统的性能。虽然高熵合金的力学行为最近一直是积极研究的主题，但晶界（GBs）在其变形行为中的作用仍知之甚少。受最近关于高熵合金的实验的启发，这些实验表明晶界充当变形孪晶的形核位点，在此，我们利用原子模拟构建了一系列具有[公式：见正文]和[公式：见正文]对称扭转晶界的等原子CoCrFeMnNi高熵合金双晶体，并研究它们在77 K下的拉伸行为和潜在变形机制。模拟结果表明，塑性变形通过晶界处部分位错的形核开始，然后随着进一步加载，通过弯曲进入块状晶体并留下堆垛层错而生长。形核应力的变化作为晶界特征的函数存在，在这项工作中由扭转角定义。我们的结果为探索将晶界作为一种微观结构设计工具来开发具有定制性能的高熵合金提供了未来的途径。
