A multiscale quasi-continuum density functional theory method was used to study the solid solution effect on dislocation nucleation during nana-indentation. Specifically, an Al thin film with Mg impurities was considered. It was found that the solid solution effect depended sensitively upon the local configuration of the impurities. Although a random distribution of the impurities increased the hardness of the material, linear distributions of the impurities actually lowered the hardness. In both cases, the strengthening/softening effects were due to dislocation nucleation. Consistent with recent experiments, the change of the ideal strength was found to be small. Different incipient plasticity behaviours were observed: in the pure material, two full dislocations were nucleated under the indentor. For a random distribution of impurities, two partial dislocations were formed instead. For linear distributions of impurities, only one partial dislocation was formed. Thus the nucleation of dislocations was sensitive to the local distribution of impurities in an alloy.

Quantum Mechanical Study of Solid Solution Effects on Dislocation Nucleation During Nanoindentation. P.Qing, Z.Xu, H.Chen, E.A.Carter, L.Gang: Modelling and Simulation in Materials Science and Engineering, 2010, 18[7], 075003