Atomistic simulation of shear-coupled motion of [1 1 0] symmetric tilt grain boundary in α-iron

Abstract

Shear-coupled grain boundary (GB) motion (SCGBM) is an important and efficacious plasticity mechanism in the deformation of metals, especially nanocrystalline metals. In this work, molecular dynamic (MD) simulation has been performed to investigate the SCGBM of two [1 1 0] symmetric tilt GBs, Σ9[1 1 0](2 2 1) and Σ17[1 1 0](2 2 3), in α-iron, and the effects of temperature and strain rate on SCGBM have been studied. The coupling factor β which is defined as the ratio of the velocities of GB lateral translation and migration was calculated, and a geometric model of β depending on the misorientation angle was constructed in [1 1 0] symmetric tilt GBs of BCC metals. The model was branched into two modes (〈1 0 0〉 and 〈1 1 1〉) corresponding to the perfect dislocation Burgers vectors in BCC metals. The β values calculated in the 〈1 1 1〉 mode were in good agreement with the MD simulation results for both the GBs. Further, the atomistic mechanisms of the SCGBM processes were also investigated. A same structural unit transformation was observed for the two GBs, which confirmed that both Σ9[1 1 0](2 2 1) and Σ17[1 1 0](2 2 3) GBs moved in the 〈1 1 1〉 mode during the SCGBM process.