Computational assessment of solute segregation at twin boundaries in magnesium: A two-factor model and solute effect on strengthening

Abstract

This work presents a comprehensive first-principles density functional theory (DFT) study of solute segregation at {101¯1} and {101¯2} twin boundaries (TBs) in Mg. A total of 56 solute elements were investigated. For each solute element, the preferential segregation sites at two TBs were identified and the associated segregation energies were computed. A two-factor model that considers both lattice strain and electronegativity, representing the mechanical and chemical effects respectively, has been proposed to predict the solute segregation energy. The model prediction shows good agreement with the DFT calculation. It was found that the mechanical effect dominates the solute segregation energy. However, depending on the site of segregation, the chemical effect can become sizable to warrant consideration. The degree of solute segregation at TBs at different temperatures was then quantified by calculating the solute concentration at TBs at different temperatures. The effect of solutes in either strengthening or weakening the TB was also evaluated. The results provide a basis for selecting promising solutes in the development of new high-performance Mg alloys.