Effects of solidification defects on nanoscale mechanical properties of rapid directionally solidified Al-Cu Alloy: A large scale molecular dynamics study
Effects of solidification defects on nanoscale mechanical properties of rapid directionally solidified Al-Cu Alloy: A large scale molecular dynamics study
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DOI：
10.1016/j.jcrysgro.2019.125255
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发表时间：
2019-12-01
影响因子：
1.8
通讯作者：
Zaeem, Mohsen Asle
中科院分区：
文献类型：
--
作者：
Mahata, Avik;Zaeem, Mohsen Asle
采用二次近邻修正嵌入原子法（2NN-MEAM）原子间相互作用势，对Al-11at%Cu合金的定向凝固过程进行了分子动力学（MD）模拟。定向凝固的条件是通过在模型边界沿着[1 0 0]凝固方向施加耗散温度来产生温度梯度。在凝固过程中，固液界面沿[1 00]方向沿着Al-Cu液相向高温端移动。在凝固的初始阶段，会形成一些凝固缺陷，如孪晶、堆垛层错和晶界。随着定向凝固的进行，晶粒沿凝固方向沿着伸长，并且在凝固的最后阶段没有新的缺陷或晶界形成。拉长的晶界沿沿着[1 0 0]形成了几层层状结构。当凝固的多晶沿[001]方向变形时，部分位错在晶界附近滑动，而在拉伸过程中，部分位错沿着[100]方向滑动，Al-Cu基体中产生一些缺陷。由于缺陷的形成需要更多的能量，当沿着[1 0 0]凝固方向变形时，凝固样品显示出更高的拉伸强度和应变。
Directional solidification of Al-11 at % Cu is investigated by molecular dynamics (MD) simulations utilizing second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potential. The condition for directional solidification is produced by imposing dissiymilar temperatures at the model boundaries along the [1 0 0] solidification direction to create a temperature gradient. During solidification, the solid-liquid front travels through the Al-Cu liquid along the [1 00] direction towards the high temperature end. M the initial stages of solidification, several solidification defects such as twins, stacking faults, and grain boundaries form. As directional solidification progresses, grains elongate along the solidification direction, and at the final stages of solidification no new defects or grain boundaries form. The elongated grain boundaries form a few layers with lamellar like structures along [1 0 0]. When the solidified polycrystalline is deformed in the [0 01] direction, glide of partial dislocations happen around the grain boundaries, whereas during elongation along [1 0 0] some defects from in the Al-Cu matrix. Since formation of defects requires more energy, the solidified samples show a higher tensile strength and strain when deformed along the [1 0 0] solidification direction.