Abstract
Shear-coupled grain boundary (GB) migration can be an efficacious mechanism to accommodate plastic deformation when the grain size of polycrystalline materials goes small. Nevertheless, how this kind of GB motion comes into play at the atomic level has not been fully revealed. Here, we have investigated the shear-coupled migration (SCM) of typical [100] group symmetrical tilt GBs in bcc W using atomistic simulations. Depending on GB character, the SCM is found to proceed via dislocation slipping in the 〈100〉 or 〈110〉 mode with striking shear strength difference between them. We demonstrate that there exists an unusual atomic shuffling along the tilt axis, which greatly assists SCM to operate in the easier 〈110〉 mode instead of the 〈100〉 one. The present results highlight the significant role of GB character in the atomistic SCM process and contribute to the future design and fabrication of high-performance materials in GB engineering.
Highlights
STGBs in W are revealed utilizing atomistic simulations based on molecular dynamics (MD) methods
We remark that the atomistic mechanism revealed here is expected to be generally applicable to the Shear-coupled grain boundary migration (SCM) process of all STGBs in bcc metals and how the present mechanism depends on temperature, velocity or defects will be a subject of future work
Analysis of the equilibrium grain boundary (GB) structures shows that the STGBs can be adequately described by the previously proposed structural unit model and dislocation model
Summary
STGBs in W are revealed utilizing atomistic simulations based on MD methods. The implications of this work are discussed. We found that for STGBs migrating in the 〈110〉 mode, there exists an inherent stress component along xz (see the methods section for the crystallographic directions) in the ground state GB structure.
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