Interfacial precipitation in {101¯2} twin boundaries of a Mg−Gd−Zn−Zr alloy

Abstract Twinning and precipitation play important roles in deformation and strengthening of magnesium alloys. In this work, interfacial precipitation in {10 1 ¯ 2} twin boundaries (TBs) of a cold-stamped Mg−12Gd−1.2Zn−0.4Zr alloy was investigated using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy. Extended periodic segregation of Gd + Zn atoms in the ∼86.2° {10 1 ¯ 2} TBs with basal-prismatic facets and in the symmetric tilting TBs (obviously > 86.2°) frequently occurred, resulted in the formation of new interfacial phases, namely βTB’ having a monoclinic structure in the TBs with two segregation layers and βTB having a tetragonal structure in the TBs with three or more segregation layers. The formation of βTB clearly accelerates peak-aging and improves the alloy's strength.