The Study Of Environmental Embrittlement Of Mg Twin

Mg alloys are increasingly being used in a wide range of applications in automotive,aircraft industries and electronic products due to their light density, high strength, highstiffness and good castability. However they have low plastic formability in roomtemperature, which limits their industrial application. It has been proved that twinformation can improve the plastic formability of Mg alloys, as well as influences theformability and the yield strength of cast Mg. Thus, it can guide the applicationenvironment and improve application efficiency of Mg alloys effectively by researchingthe effect of common environment elements on Mg twin.In this paper, we carried out first-principle calculations to study the effect of H, O andN on the common twins in Mg, namely,{1011},{1012}, and {1013}twins. The moststable solid solution positions of H, O and N in the above twins were determined. Theeffect of those solid solution elements on twin cleavage energy, electron localizationfunction and density of states were also calculated.According to the calculation results, for {1011}and {1012}twins, the most stablesolid solution positions for both H and O are on the twin boundaries, while these for Natoms are in the interior of twins. As for {1013}twin, the solid solution ofenvironmental impurities makes twinning disappearance. Those can maintain twinstructures have high energies, which means they are in metastable states. The variation oftwin cleavage energies before and after solid solution indicates that H makesembrittlement in {1011}twin, while O and N do not. In {1012}twin, all these solidsolution elements make embrittlement and the efficiency follows H> O> N. In {1013}twin, both H and O cause embrittlement with H more efficient, while the solid solution ofN dose not induce the similar result. The calculation results of electron localizationfunction and density of states show that all the three kinds of solid solution elementsconnect with Mg atoms through metallic bonds. Their solid solution will not affect themetal nature of Mg twins.