采用二元晶体相场模型研究了Kirkendall效应诱发的相界空洞的形成及扩展过程. 模拟结果表明: 对于取向差角较小的相界, 空洞向原子迁移率高的一侧(a相) 方向移动, 空洞的形状由最初的平行四边形向六边形演化, 空洞周围原子湮没速率大于产生速率, 从而造成空洞扩大, 空洞扩展过程中伴有相界的移动及相的长大和缩小. 对于取向差角较大的相界, 空洞还会沿相界方向扩展, 使得空洞连通, 将相界割裂开, 割裂后的两侧相界呈现锯齿状. 扩散过程中, 体系的自由能逐渐降低. 对于取向差角较小的相界, 原子迁移率差值增大, 自由能下降无明显差异. 对于取向差角较大的相界, 原子迁移率相差越大, 自由能下降速率越快. 随着相界取向差角的增大, 自由能的下降速率逐渐增大. 相界空洞的模拟结果与实验观察一致.

The mechanical properties of materials are related to the integrity of interfaces (phase and grain boundaries). For substitutional alloys, the Kirkendall voids tend to form more easily at the phase boundary or grain boundary when the atomic mobilities of different species are unequal, which will degrade the bounding quality of interfaces. So far, there have many experimental studies on the evolution of Kirkendall voids and the formation mechanism. However, allowing for the fast process of the Kirkendall voids from formation to evolution, it is hard to capture such process in real experimental conditionals. So the formation and evolution mechanism of the Kirkendall void need to be studied. A binary phase field crystal model was used to simulate the process of void formation and expansion at phase boundaries induced by the Kirkendall effect. Simulated results show that for the low misorientation phase boundary (PB), the void moves toward the side with large atomic mobility (a phase) and the void shape evolves from the initial parallelogram to hexagon. The atomic annihilation rate around a void is faster than that of growth rate, which results in void expansion. The PB migration, phase growth and shrinkage can also be observed in void expansion. For the large misorientation PB, voids can also expand along the PB direction, resulting in the connection of voids, therefore, the PB is separated and presents zigzag shape. In the interdiffusion system, the free energy decreases. The descending speed of the free energy is almost equal for the low misorientation PB while is increasing for the large misorientation PB when the atomic mobility difference becomes larger. The descending speed of the free energy is proportional to PB misorientations. The PB void predicted from our computer simulation is consistent with the experiment observation.