温度梯度下Zr晶界迁移的分子动力学研究

Molecular dynamics study of grain boundary migration in Zr under temperature gradient

定向退火技术广泛应用于提升高温合金综合性能,其构建温度梯度环境驱动晶界定向迁移,获得性能优异的柱状晶组织。然而,不同晶界的迁移能力差异较大,对柱状晶组织的形成造成阻碍。为了更好的调控定向退火工艺,本研究采用分子动力学方法对α-Zr中多个晶界在温度梯度下的迁移行为进行研究,归纳不同晶界在迁移过程中能量变化特征与迁移行为之间的规律,阐明超额势能与预熔温度等因素影响晶界迁移的机理。研究发现,原子势能越高则迁移激活焓越低,预熔温度越低则驱动力越大,晶界越容易发生迁移。这一发现可为解释温度梯度环境下晶粒的异常长大与晶界的停止迁移提供理论依据,为更好调控此类合金微观组织、获得均匀柱状晶提供理论参考。

Directional annealing technology is widely used to enhance the comprehensive performance of high-temperature alloys by creating a temperature gradient environment to drive the directional migration of grain boundaries,resulting in the formation of superior columnar grain structures.However,significant differences in the migration abilities of different grain boundaries hinder the formation of columnar grain structures.In order to better control the directional annealing process,this study employed molecular dynamics simulations to investigate the migration behavior of multiple grain boundaries in a-Zr under temperature gradients.The regularities between the energy change characteristics and migration behavior of different grain boundaries during the migration process were summarized,elucidating the mechanism of grain boundary migration influenced by factors such as excess energy and pre-melting temperature.The study found that higher atomic potential energy leads to lower migration activation enthalpy,and lower pre-melting temperature results in greater driving force,making grain boundary migration easier.This finding provides a theoretical basis for explaining the abnormal growth of grains and the cessation of grain boundary migra-tion under temperature gradient environments,and offers theoretical references for better controlling the microstructure of such alloys and obtaining uniform columnar grains.