Critical shear stresses at aluminum–silicon interfaces

In the present study, the critical shear stress (CSS) for various Al/Si and Al/Al interfaces was determined using molecular dynamics and MEAM potential for different alignments (normal to the interface) and orientations (parallel to the interface). Bond angle distribution, pair correlation functions and shortest path ring analysis were used to determine the nature of plastic deformation due to the sliding. These analyses showed that the deformation is localized within an approximately 10 Å region near the interface only on the Al side. The critical shear stress of Al/Si interface was found to be significantly lower than the critical tensile stress due to the partial stick–slip in sliding. In addition, it was proven that there is not an explicit relationship between shear and tensile critical stresses, which is dramatically different from isotropic materials, where the shear stress is about half of the tensile stress. The misorientation effects differ dramatically in homogeneous Al/Al interfaces and in heterogeneous Al/Si interface: the misorientation can reduce the CSS at Al/Al interfaces by two orders of magnitude; while it has negligible effect on CSS in Al/Si. The only CSS of Al/Al larger than that of the Al/Si interfaces occurs when two Al surfaces are perfectly aligned and oriented into a single crystal. Therefore, in general, introducing Si improves its strength for different grain orientations.