纳米晶Al-xMg铝合金的元素再分布及其对强度的影响

Redistribution of Solute Atoms in Nanocrystalline Al-xMg Aluminum Alloy and Its Effect on Strength

目的针对Al-Mg合金在变形加工过程中容易出现的溶质元素再分布现象,通过微观表征和定量计算深入研究元素再分布的相关机制及其强度贡献。方法利用扫描透射电镜高角环形暗场技术结合几何相位分析,详细研究了溶质元素再分布机理,对经过高压扭转后不同Mg含量的Al-Mg合金中的元素分布进行了表征,并通过原子探针层析技术对原子的三维空间分布情况进行了团簇分析。结果随着Mg的原子数分数从1.0%增加至8.0%,合金硬度从129.0HV显著上升至223.6HV。合金内部的溶质分布状态可以分为溶质原子贫化、溶质原子富集和溶质原子不均匀分布3种,剧烈塑性变形引入的不均匀微观应变诱导了Mg原子的再分布。结论合金中形成的大量原子团簇为Al-8Mg合金贡献了47.7HV的硬度值,占总硬度的21.3%,溶质团簇对合金强度的强化效果十分显著,表明团簇强化是材料强化手段中不可或缺的新型强化机制。

The work aims to conduct in-depth research on the mechanisms and strengthening contribution of element redis-tribution through microscopic characterization and quantitative calculation to deal with the phenomenon that solute element re-distribution is easily introduced to Al-Mg alloys during deformation processing.The scanning transmission electron microscopy high angle annular dark field technology was used in combination with geometric phase analysis to study the mechanism of sol-ute element redistribution.The element distribution in Al-Mg aluminum alloys with different Mg contents after high-pressure torsion was characterized,and the three-dimensional spatial distribution of atoms was analyzed through cluster analysis using the atomic probe tomography technology.The results showed that as the Mg content increased from 1.0at.%to 8.0at.%,the hardness increased from 129.0HV to 223.6HV.The solute distribution inside the alloy could be summarized as three states:sol-ute atom depletion,solute atom enrichment,and solute atom inhomogeneous distribution.The inhomogeneous microstrain in-troduced by severe plastic deformation induced the redistribution of Mg atoms.The contribution of cluster strengthening to the hardness of Al-8.0Mg alloy was calculated to be 47.7HV,accounting for 21.3%of the total hardness.It can be seen that solute clusters have an important strengthening effect on the strength.This indicates that cluster strengthening is an indispensable new strengthening mechanism in material strengthening methods.