Abstract
The formation of Zn and Mg segregations at a tilt Σ5{013} <100> grain boundary (GB) in Al and the effects of these solutes on deformation behavior of polycrystalline Al were investigated using ab initio total energy calculations. Using a step-by-step modeling of the segregation process, we found that the formation of a thick segregation layer of Zn at the GB is energetically preferable, while the formation of an atomically thin segregation layer is expected in the case of Mg. To reveal the effect of segregation on the cohesive properties of Al GBs, we calculated the energy of cleavage decohesion and the shear resistance for GB sliding. We show that the segregation of Zn results in a substantial decrease in barriers for GB sliding, while the segregation of Mg increases the barriers. The results obtained allow us to explain experimental findings and demonstrate a strong relationship between chemical bonding of solute atoms, their segregation ability, and GB strength.
Highlights
Metals 2021, 11, 631. https://Grain boundary (GB) segregation frequently occurs in polycrystalline materials, affecting their properties, such as strength and plasticity, and influencing the kinetics of important processes such as recrystallization, solid solution decomposition, new phase nucleation, etc. [1]
The exchange-correlation energy was calculated in the generalized gradient approximation (GGA) by using the formalism proposed in Ref. [33]
Similar observations were previously reported in Reference [16]; some numerical differences with the results presented here may be ascribed to a different grain boundary (GB) being considered in Reference [16]
Summary
Metals 2021, 11, 631. https://Grain boundary (GB) segregation frequently occurs in polycrystalline materials, affecting their properties, such as strength and plasticity, and influencing the kinetics of important processes such as recrystallization, solid solution decomposition, new phase nucleation, etc. [1]. Grain boundary (GB) segregation frequently occurs in polycrystalline materials, affecting their properties, such as strength and plasticity, and influencing the kinetics of important processes such as recrystallization, solid solution decomposition, new phase nucleation, etc. Scientific interest in the segregation of solute elements to GBs was recently revived in connection with the development of new ultra-fine-grained (UFG). Layers of Zn atoms are distributed homogeneously along GBs in an alloy [5,12]. These specific segregations are thought to be one reason for the increased strain rate sensitivity and GB sliding enhancement at relatively low temperatures in UFG Al-Zn alloys, which result in super-ductility [6,13,14]
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