Wanghui Li , Meizhen Xiang , Zachary Howard Aitken , Shuai Chen , Yilun Xu , Xinyu Yang , Qingxiang Pei , Jian Wang , Xiaoyan Li , Guglielmo Vastola , Huajian Gao , Yong-Wei Zhang
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引用次数: 0
Abstract
The transition from Hall-Petch (HP) to inverse Hall-Petch (IHP) behaviors associated with grain size reduction has been recognized for over two decades. However, the underlying mechanisms for such transition in high entropy alloys (HEAs) under dynamic loading, in which abundant deformation mechanisms could be activated either sequentially or simultaneously, remain unclear. Here, we investigate the HP to IHP transition in nanocrystalline CoCrFeMnNi HEAs under shock loading by examining their deformation mechanisms and flow stresses using large-scale molecular dynamics (MD) simulations. It is found that this transition is strongly dependent on the shock pressure as a result of the complex interplay among multiple competing deformation mechanisms, including the hardening mechanisms such as dislocations interactions and grain boundary (GB) blocking, as well as the softening mechanisms like phase formation, amorphization, GB thickening, and grain rotation. Moreover, there exists a critical shock pressure, which corresponds to the largest critical grain size for the HP-IHP transition. Below the critical shock pressure, the critical grain size increases with pressure due to a stronger hardening effect in grain interior (GIs), while above the critical pressure, the critical grain size first decreases and then undergoes a pressure-insensitive plateau before further decrease due to softening effects in GIs. A theoretical model that includes different deformation mechanisms is proposed for the first time to capture the shock pressure-dependent HP-IHP transition. Our work provides valuable guidance for optimizing the grain size of nanocrystalline HEAs for applications involving dynamic loadings.
期刊介绍:
International Journal of Plasticity aims to present original research encompassing all facets of plastic deformation, damage, and fracture behavior in both isotropic and anisotropic solids. This includes exploring the thermodynamics of plasticity and fracture, continuum theory, and macroscopic as well as microscopic phenomena.
Topics of interest span the plastic behavior of single crystals and polycrystalline metals, ceramics, rocks, soils, composites, nanocrystalline and microelectronics materials, shape memory alloys, ferroelectric ceramics, thin films, and polymers. Additionally, the journal covers plasticity aspects of failure and fracture mechanics. Contributions involving significant experimental, numerical, or theoretical advancements that enhance the understanding of the plastic behavior of solids are particularly valued. Papers addressing the modeling of finite nonlinear elastic deformation, bearing similarities to the modeling of plastic deformation, are also welcomed.