Nanoscale contact behavior of (111) fcc metallic surfaces

M Khajehvand and H Seppanen and P Sepehrband, COMPUTATIONAL MATERIALS SCIENCE, 170, UNSP 109149 (2019).

DOI: 10.1016/j.commatsci.2019.109149

With the use of molecular dynamics simulations, the contact between two substrates made of the same material is investigated for three different fcc metals: Al, Cu, and Ag. For this purpose, two misoriented substrates containing (1 1 1) planes parallel to their surfaces are placed at varied interfacial separations and allowed to form a contact. While JC happens in all three materials, it is shown that, as opposed to Al and Ag, Cu exhibits a smooth jump-to-contact (JC) behavior, meaning that for separations just above the critical distance for JC, the two surfaces get closer to each other, but they do not form a contact. On the other hand, for separations below the critical distance, JC occurs, and dislocations are generated at the interface due to the misorientation between substrates. It is seen that under favorable conditions, the interfacial dislocations can multiply, primarily because of the strain that exists in the system due to the initial interfacial separation. The possibility of occurrence of dislocation multiplication is found to be higher at high contact temperatures, high strain values, and low misorientation angles. Also, Al is found to be less prone to dislocation multiplication, compared to Ag and Cu. Most importantly, it is observed that the predominant mechanism for dislocation multiplication in Al is cross-slip of interfacial dislocations, whereas in Ag and Cu it is the nucleation of partial dislocations from the interface.

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