Transition from grain boundary migration to grain boundary sliding in magnesium bicrystals

ZY Xing and HD Fan and CL Xu and GZ Kang, ACTA MECHANICA SINICA, 40, 123448 (2024).

DOI: 10.1007/s10409-024-23448-x

In polycrystalline magnesium (Mg) and Mg alloys, as the grain size decreases, the grain boundary (GB) mediated plasticity including GB sliding and GB migration becomes the dominant deformation mechanism. In this study, the motion of 1\bar 100 symmetric tilt GBs in Mg bicrystals is investigated using molecular dynamics (MD) simulations. The effects of GB misorientation angle and temperature are considered. At low/room temperatures and varied GB misorientation angles in the range of theta >= 58.36 degrees, the GB migration occurs via the shear coupling with the invariant plane of 0001; At 35.80 degrees < theta < 58.36 degrees, both the GB migration and GB sliding happen and the invariant plane changes from 0001 plane to 11\bar 22 plane; At 26.54 degrees <= theta <= 35.80 degrees, the GB migrates with the invariant plane of 11\bar 22; Finally, at theta < 26.54 degrees, the GB sliding becomes the main deformation mechanism. At 700 K, the GB sliding occurs at the misorientation angles in the range of theta < 58.36 theta; while the GB migration occurs at the misorientation angles of theta >= 58.36 degrees. By comparing the energy barriers of GB migration and GB sliding, it yields that the deformation mode with a low energy barrier always happens, which leads to the transition of deformation modes and agrees well with the MD simulation results.

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