Phase-field crystal study of segregation induced grain-boundary premelting in binary alloys

The segregation-induced grain boundary (GB) premelting is studied by phase-field crystal model. We investigate the microstructure evolution of GBs with different misorientation angles and the variation of concentration distribution during premelting process. The liquid film thickness is calculated by an excessive mass technique. The results show that for low-angle GBs, the liquid phase first appears at individual dislocations region where the solute atoms segregate, and there exist two structural transitions during premelting process, which behave as two inflection points in the curve of w   versus ΔB0ΔB0. For high-angle GBs, the liquid film is rather uniform and its thickness diverges logarithmically when the melting point is approached. Moreover, the higher misorientation angle and segregation the GB has, the lower temperature the liquid film occurs. The concentration variation law indicates that GB segregation and GB premelting promote each other when the liquid phase appears. The critical wetting angle is almost equal to 12.5° and this value is much closer to the reality.