Evolution of solidification defects in deformation of nano-polycrystalline aluminum
Evolution of solidification defects in deformation of nano-polycrystalline aluminum
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DOI：
10.1016/j.commatsci.2019.03.034
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发表时间：
2019-06-01
影响因子：
3.3
通讯作者：
Zaeem, Mohsen Asle
中科院分区：
文献类型：
--
作者：
Mahata, Avik;Zaeem, Mohsen Asle
采用分子动力学(MD)模拟方法研究了凝固多晶铝(Al)单轴拉伸变形过程中凝固缺陷的形成及其演化规律。首先，对凝固过程进行了等温模拟和不同淬火速率下的模拟。在形核的初始阶段，根据淬火速度或过冷温度，形成共格孪晶界和/或五重孪晶。凝固后的多晶铝由随机分布的晶界、孪晶界和空位组成。研究了不同温度和应变速率下凝固Al单轴拉伸变形过程中纳米组织和缺陷的演化规律。在单轴变形过程中，观察到晶界空洞的形成以及预先存在的凝固孪晶和形变孪晶的脱孪生。实验还发现，变形温度比外加应变速率对凝固样品强度的影响更大。对于晶粒度小于10 nm的固化体，屈服强度和弹性模量随晶粒度的增大而增大，表现为相反的Hall-Petch关系。分子动力学模拟结果表明，单晶铝具有较高的屈服强度，而多晶铝具有较大的塑性变形。
Formation of solidification defects and their evolution in uniaxial tensile deformation of solidified polycrystalline aluminum (Al) were investigated by molecular dynamics (MD) simulations. First, solidification process was simulated both isothermally and with different quench rates. At the initial stages of nucleation, coherent twin boundaries and/ or fivefold twins formed depending on the quench rate or the undercooling temperature. The solidified polycrystalline Al consisted of randomly distributed grains, twin boundaries, and vacancies. Evolution of nanostructures and defects in uniaxial tensile deformation of solidified Al under different temperatures and strain rates were studied. Void formation at grain boundaries and detwinning of preexisting solidification twins and deformation twins were observed during the uniaxial deformation. It was also found that the temperature of deformation has a stronger effect than the applied strain rate on the strength of solidified samples. For solidified cases with grain sizes lower than 10 nm, the yield strength and Young's modulus increased with increasing grain size, indicating an inverse Hall-Petch relationship. Similar to experimental data, MD simulations showed a higher yield strength for single crystal Al and a large plastic deformation for polycrystalline Al.