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镁元素可以降低铝的本征层错能,因而Al-Mg合金被认为具备孪晶变形的潜力。然而在多种大变形Al-Mg合金中很难发现变形孪晶。为了探究Al-Mg合金的孪晶变形潜能,采用第一性原理计算研究镁和空位对铝广义层错能的影响。研究发现Mg和空位均具有层错Suzuki偏析特性,并且会降低Al的本征层错能。但是随着镁含量的提高,铝的本征层错能不会持续降低,孪晶特性参数τa也不会持续升高。基于Al-Mg合金的孪晶特性参数τa,我们预测即使在高固溶镁含量下,Al-Mg合金依然很难发生孪晶变形。镁和空位所引起的本征层错能的降低在一定程度上能够提高大变形Al-Mg合金的加工硬化速率并且促进变形带的形成。
Magnesium reduces the intrinsic layer error of aluminum and Al-Mg alloys are therefore considered to have the potential for twinning. However, it is difficult to find deformation twin in many large deformation Al-Mg alloys. In order to explore the twinning deformation potential of Al-Mg alloy, the first-principles calculations were used to study the effects of Mg and vacancy on the generalized stacking fault energy of aluminum. It has been found that both Mg and vacancy have the layered fault Suzuki segregation characteristics and reduce the intrinsic layer fault energy of Al. However, as the magnesium content increases, the intrinsic layer error of aluminum will not decrease continuously, and the twins characteristic parameter τa will not increase continuously. Based on the twins characteristic parameter τa of Al-Mg alloy, we predict that the Al-Mg alloy is still hard to deform twin even at high solid solution magnesium content. The reduction of intrinsic layer fault energy caused by magnesium and vacancy can improve the work hardening rate of large deformed Al-Mg alloy to a certain extent and promote the formation of deformation zone.