纯Al<111>对称倾斜晶界迁移行为温度相关性的分子动力学研究

Effect of Temperature on Migration Behavior of<111>Symmetric Tilt Grain Boundaries in Pure Aluminum Based on Molecular Dynamics Simulations

选取具有不同取向差角的纯Al<111>对称倾斜晶界,采用合成驱动力法模拟晶界在300~800 K温度下的迁移行为,研究温度对迁移行为的影响。结果表明,晶界迁移行为的温度相关性随取向差角而变化,可以归为3类:取向差角为8.61°~21.79°的晶界呈现明显反热激活迁移,38.21°~60°晶界总体上表现为热激活迁移,27.80°~32.20°晶界在低温下为热激活迁移,在较高温度下转变为反热激活迁移。8.61°~21.79°晶界的迁移率总体上远高于其他晶界,但差异随温度升高而减小。结构单元模型能够准确体现不同晶界在各个温度下的结构特点,且结构单元类型相同的晶界表现出相似的迁移行为温度相关性。不同温度区间内同一晶界的迁移行为温度相关性变化可能与结构单元多个变体之间的转变有关。

The migration behavior of<111>symmetric tilt grain boundaries(GBs)having different misorientation angles was simulated using a molecular dynamics synthetic driving force method.The effect of temperature on the migration behavior was investigated in the temperature range of 300-800 K.The results demonstrated that the temperature dependencies of GB migration varied with the misorientation.GBs with a misorientation of 8.61°-21.79°exhibited antithermally activated migration,whereas those with a misorientation of 38.21°-60°exhibited thermally activated migration.For the GBs having a misorientation of 27.80°-32.20°,there was an apparent transition from thermally activated migration at low temperature to antithermally activated migration at high temperature.The mobility of the GBs having a misorientation of 8.61°-21.79°was much higher than that of other GBs,but the differences between them decreased with increasing temperature.The GB structures at different temperatures can be well described using the structural unit model.GBs with structures consisting of similar types of structural units exhibit comparable temperature dependencies in their mobility.The complex temperature dependencies of migration behavior shown by some GBs appear to be related to structural changes featured by the transformation between variants belonging to the same type of structural units.