采用相场方法模拟了Ti-Al-Nb合金α2→ O相转变, 探讨了有无外力场作用下弹性应变能对O相颗粒形貌、取向、数目、体积分数及平均尺寸的影响. 结果表明: 在弹性应变能作用下, 颗粒形貌为长方块状, 且沿弹性软方向分布; 无外力场时, 弹性应变能越大, 沉淀相越易形核, 稳定时颗粒数目越多, 体积分数及平均尺寸越小; 在外力场作用下, 取向有利的变体优先长大, 取向不利的变体长大受到抑制; 在较小压应力作用下, 沉淀相易于形核, 稳定时颗粒数目增多, 体积分数减小; 在拉应力或较大压应力作用下, 应力越大, 越难于形核, 稳定时颗粒数目越少, 体积分数越大.
The Ti-Al-Nb alloys have received significant attention due to its excellent properties for high-temperature applications. The α2→ O phase transformation taking place in these alloys leads to complex multi-variant and multi-domain microstructure, which has been extensive researched by experimental studies. The morphology, size, spatial arrangement of multi-variant and the volume fraction of precipitated phase, which are determined by the elastic strain energy, affect the important physical and mechanical properties of these alloys. So it is important to examine the effect of elastic strain energy on coarsening dynamics during the α2→ O phase transformation. In this study, phase-field method has been used to simulate the α2→ O phase transformation, and the effect of elastic strain energy on coarsening dynamics especially the morphology, orientation, number and the volume fraction of precipitated phase particles have been discussed. The results show that elastic strain energy has great impact on the morphology and orientation of precipitated phase particles. As the result of elastic strain energy, particles transformed into block and aligned along the elastic soft directions. The greater elastic strain energy in system without applying any external stress, the easier nucleation and the smaller volume fraction and mean size of particles when system was steady. An applied stress can result in the selective growth of precipitated phase variants, which promotes the precipitation of favored variants and retards the precipitation of other variants, finally changes the morphology. When system applied small pressure stress, the number of particles increased which eventually led to the reduction of mean size. Volume fraction of precipitated phase increased with increasing external stress when it is over a certain extent.
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