相场法模拟应力时效过程中共格有序第二相的析出和粗化

Precipitation and Coarsening of Coherent and Ordered Second Phase during Stress Aging by Using Phase-Filed Simulations

采用双场耦合条件下的宏观相场法,实现了模拟外加应力下无序基体中共格有序第二相的析出和粗化。结果发现,在外加应力下,第二相颗粒将发生定向粗化,形成筏状组织,成筏的方向取决于外加应力的性质、点阵错配的正负以及两相的弹性模量差。沉淀体积分数越大,颗粒合并和反相畴界对沉淀形貌的影响越显著,导致许多颗粒呈现不规则形貌。颗粒的对齐有两种机制,一是链条外颗粒的溶解,一是颗粒的迁移。在粗化过程中,多颗粒体系首先通过前1种机制形成链条,然后通过第2种机制使链条进一步对齐。

The microstructural evolution during the precipitation and coarsening of the ordered second phase in multiparticle coherent systems under stress applied is simulated using the phase-field methods. The results show that the rafted microstructures develop as a result of directional coarsening when uniaxial loads are applied. The rafting direction is depended on the applied load, the lattice misfit between the γ, and γ′ phases and the differences between the elastic constants of the two phases. When the volume fractions of the second phase become large, the coalescence and antiphase domain boundary （APB） will have more pronounced effects on the morphologies of the second phase. There are two mechanisms responsible for the particle alignment： the first is the solution of particles out of chains and the second is the migration of particles. Most of chains are established firstly through the first mechanism, then the second one to further alignment.