微观相场法研究沉淀早期两相竞争对筏化的影响

基于微观相场动力学模型,研究沉淀早期不同成分Ni-Al-V合金时效时有序相的生长和组织生长方向的变化。结果表明:沉淀早期有序相间的竞争生长会很大程度地影响合金的形貌及生长方向。在一定的温度、应力场作用下,Al含量较低时,DO22有序相先析出,DO22相颗粒数量较多、尺寸较小,有序相的筏化不明显,合金整体上无显著的筏化现象;Al含量稍高时,L12相先析出,DO22相颗粒数量较少、尺寸较大,组织在[010]方向上发生一定程度的择优生长;Al含量较高时,L12相先析出,DO22相颗粒数量继续减少、尺寸继续增大,组织在[100]方向上显示出较强的筏化趋势;较低温度时效的合金L12有序相析出提前,组织的筏化趋势较弱。

Influence of the Competitive Growth between Two Phases on Rafting during Early Precipitation through Microscpic Phase-Field

Based on the microscopic phase-field kinetic model, the growth of the ordered phase and the growth direction change of the structure during the early precipitation for Ni-Al-V alloys with different components when aging were investigated. The results show that during the early precipitation the competitive growth between ordered phases may greatly influence the shape and growth direction of alloys. Under the condition of certain temperature and elastic stress, when the Al content is lower, DO22 ordered phases precipitate first, which are numerous and small, the rafting of the ordered phase is not obvious and there is not remarkable rafting for the whole alloys. When the Al content a little higher, L12 phases precipitate first, DO22 phases become less and bigger, and the structure preferentially grows along [100]. When the Al content is much higher, L12 phases precipitate first, and the DO22 phase becomes less and bigger continuously, while the structure exhibits a strong rafting trend along [100]. Aged at a lower temperature, L12 ordered phase precipitates ahead and the rafting trend is weaker