Abstract
Using the MD / MC Metropolis scheme, the most probable fracture-surface (FS) structures formed on a cleavage plane were studied in simulations of Al-3 at.% Mg and Al-3 at.% Ni alloys containing symmetric Σ5{013}<100> and Σ5{012}<100> boundaries with superstructures of segregations. The effect of FS ordered structures on grain-boundary (GB) decohesion processes is currently not studied, although the effect of an individual impurity atom on the features of grain-boundary fracture has been studied in detail. The resulting FS structures were analyzed depending on the type of grain boundaries and impurity atoms. It has been shown that the formation of FS superstructures reduces the energy of decohesion in all cases. The decrease in cohesive strength is most noticeable in Al-Ni compared to Al-Mg. A microscopic mechanism of the segregation formation and related GB reconstruction in Al alloys was revealed. For the solutes that have a larger atomic size and accept electrons from the matrix (such as Mg), one can assume that the deformation contribution will be dominant. It can be assumed that during FS superstructure formation, a preferred position of Mg is determined by the extra volume at the cleavage planes and / or reduced number of nearest neighbors. As a result, FS superstructures for the Al-Mg alloy are close to GB structures. The presence of directional bonds, as for the Al-Ni alloy, significantly changes FS structures. For both types of Σ5 GBs, stepped FS superstructures form directly under the cleavage planes.
Funding
1. The work was carried out as part of the state assignment of the Ministry of Education and Science of the Russian Federation for IMP Uran Ru - The work was carried out as part of the state assignment of the Ministry of Education and Science of the Russian Federation for IMP Uran Ru