利用晶体相场模拟晶界的预熔以及熔化现象, 研究不同取向差角度时, 预熔及熔化的微观 组织形貌,并且采用过剩质量方法定量计算预熔及熔化时晶界处液相薄膜宽度. 研究表明, 在接近熔点时, 晶界处预先出现一层液相薄膜,液相膜的形态与晶界处的取向差角度有关. 当取向差角为大角晶界时, 液相膜沿晶界均匀稳定分布; 当取向差角为小角晶界时,若干由液相区包围的独立位错均匀分布在晶界处, 随着温度逐渐接近熔点, 晶界处发生结构转变: 独立位错两两合并, 原来小的液相区也相应合并成为较大的“液相池”. 这种结构转变不仅出现在预熔时, 而且发生在 过热状态下, 在液相宽度曲线图上表现为宽度“跳跃”性增大. 同时, 晶体相场模型计算得到的临 界润湿角θ_c为12°, 较Read－Shockley理论所得的数值更接近实际结果.

The presence of grain boundary (GB) premelting can alter macroscopic properties of polycrystalline materials, which lead to catastrophic material failure as exemplified by hot cracking during high temperature processing of metallic alloys. Since the premelting is considered to occur in a very limited region, it is difficult to image and to measure thermodynamic properties of nanoscale width of liquid films. At the microscopic level capturing crystalline details, atomistic modeling techniques such as Monte－Carlo (MC) or molecular dynamics (MD) have been widely adopted, however, these methods can't be used to observe morphology of GB at atomic level. Phase field crystal (PFC) has the advantage of resolving the atomic scale density wave structure of a polycrystalline material, it naturally incorporates elastic and plastic deformations and multiple crystal orientations and can be used to study a host of important material processing phenomena. The GB premelting and melting were investigated by PFC method, microstructure evolution of premelting and melting under different misorientation angles were discussed and the film width of GB was quantitively compute in terms of the excess mass method. The results showed that the liquid film appears as the melting point is approached from below, and the morphologies of liquid film are related to misorientation angle. When misorientation angles are high－angle GB, the liquid film are homogeneous. For low－angle GB, the individual dislocations which are surrounded by liquids are uniform distributed in the GB, as the melting point is approached, structure transition occurs as follows: the dislocations form pairs and the original liquids are also combined a big “liquid pool”. This structure transition not only appears during the period of premelting, but also occurs in the overheated stage, which presents a jump in the film width picture. Critical wetting angle is 12° computed by PFC method, it is more closer to the actual results than the value obtained from the Read－Shockley theory.