Two-dimensional phase-field simulations of dendrite competitive growth during the directional solidification of a binary alloy bicrystal
Two-dimensional phase-field simulations of dendrite competitive growth during the directional solidification of a binary alloy bicrystal
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DOI：
10.1016/j.actamat.2014.08.035
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发表时间：
2014-12
期刊：
影响因子：
9.4
通讯作者：
T. Takaki;M. Ohno;T. Shimokawabe;T. Aoki
中科院分区：
文献类型：
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作者：
T. Takaki;M. Ohno;T. Shimokawabe;T. Aoki
采用二维相场模拟的方法，研究了Al-Cu合金定向凝固过程中双晶收敛晶界(GBs)枝晶的竞争生长。特别关注了最近观察到的镍基高温合金定向凝固过程中的异常过度生长现象，其中有利取向(FO)枝晶被不利取向(UO)枝晶过度生长。通过在图形处理单元上进行并行计算，加速了相场模拟。模拟结果表明，Al-Cu合金中出现了异常的过生长现象，表明这种现象在金属材料中是普遍存在的。FO枝晶和UO枝晶前扩散层的不同对收敛晶界枝晶的竞争生长和异常过生长起主导作用。此外，在所有的FO枝晶中观察到了异常的过度生长，其间距允许枝晶阵列稳定地生长而不需要改变枝晶的数量。当GB处的FO枝晶与下一个FO枝晶之间的间距近似等于临界最小间距时，GB处的FO枝晶被UO枝晶过度生长。然而，对于大倾角的UO枝晶，没有观察到异常的过度生长。在这种情况下，所有的UO树枝晶都被GB处的FO树枝晶阻止，FO树枝晶向UO树枝晶迁移。
We investigated the competitive growth of dendrites at the converging grain boundaries (GBs) of bicrystals during the directional solidification of an Al–Cu alloy by means of two-dimensional phase-field simulations. In particular, the focus was on the recently observed phenomenon of unusual overgrowth during the directional solidification of a Ni-based superalloy, where the favorably oriented (FO) dendrites are overgrown by the unfavorably oriented (UO) ones. The phase-field simulations were accelerated by parallel computations on graphics processing units. The simulation results showed that unusual overgrowth occurs in Al–Cu alloys, indicating that this phenomenon is a common one in metallic materials. It was also concluded that the differences in the diffusion layers in front of the FO and UO dendrites had a dominant effect on the competitive growth of dendrites at the converging GB as well as on the unusual overgrowth. In addition, unusual overgrowth was observed in all the FO dendrites with a spacing that allowed the dendrite array to grow stably without necessitating a change in the number of dendrites. The FO dendrite at the GB is overgrown by the UO dendrite when the spacing between the FO dendrite at the GB and the next FO dendrite is approximately equal to the critical minimum spacing. However, the unusual overgrowth was not observed for UO dendrites with a large inclination angle. In this case, all the UO dendrites are blocked by the FO dendrite at the GB, and the FO dendrites migrate toward the UO dendrites.