Formation mechanism of co-axial grain boundaries in a Mg alloy

Due to the insufficient slip systems in hexagonal close-packed structure, twinning is frequently activated to support stable plastic defor-mation of Mg alloy. In this work, we found four typical twin-like interfaces with misorientations of 102 degrees, 109 degrees, 142 degrees and 149 degrees, respectively, which had not only a shared [11 2 0] zone axis of neighboring grains, but also overlapped diffraction spots similar to twins. However, high -resolution transmission electron microscope (HRTEM) analysis revealed that the interfaces in real space deviated from the supposed twinning planes in reciprocal space, i.e. their overlapped diffraction spots. We clarified that the incoherent interfaces were co-axial grain boundaries (CGBs). Additionally, a special angle of 0, close to 90 degrees, between the interface and one side of basal plane, was frequently formed in CGBs. We proposed that interaction of multiple twinning contributes to the formation of CGBs, and the 0 is formed due to alternative tensile and compression twinning under a uniaxial loading.(c) 2022 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Automated summary

In this study, four typical twin-like interfaces were identified as incoherent grain boundaries. It was proposed that the interaction of multiple twinning contributes to the formation of these boundaries, and a special angle close to 90 degrees is formed due to alternative tensile and compression twinning under uniaxial loading.