Segregation of solute elements and their effects on the strength of Al Σ5 (210) [001] symmetrical tilt grain boundary in 2219 alloys

摘要

Through the first-principles calculations based on quantum mechanics, systematic study has been made into the segregation of solute elements (Cu/Mn/Fe/Si/Zn/Mg/Zr/V/Ti) and their effects on the Al Σ5 (210) [001] symmetrical tilt grain boundary (STGB) in 2219 alloys, which provides a theoretical basis for optimizing the distribution of solute elements. The calculation results show that Zr and Mg atoms have a spontaneous tendency to segregate in the direction of Al Σ5 (210) [001], while other atoms, Ti atoms in particular, are more likely to stay in the grains. At the same time, the first-principles computational tensile test (FPCTT) shows that the GB segregation of most solute elements is beneficial to improve the bonding strength of the materials. V element can improve the separation energy and enhance the bonding strength to the greatest extent, while Mg and Zn elements would reduce the separation energy and lead to the decrease of the theoretical tensile strength. The analysis results of charge density and density of states show the embrittlement induced by Mg atoms and strengthening effect of V atoms depend very much of two factors: atomic size and charge density. The strengthening effect of V atoms lies in the resonance hybrid occurring in s-electrons and p-electrons. While the embrittlement induced by Mg atoms is due to the combination of GB expansion and charge density depletion. In the same way, we can try to reasonably explain the influence mechanism of other elements on the macroscopic properties of the alloys from the atomic and electronic level.