As strength of crystalline materials strongly depended upon their ability to nucleate new dislocations or move the existing ones, a proper knowledge of factors that played a major role at the first stages of plastic deformation was highly desirable. However, fundamental understanding of the role of point defects, such as vacancies or inclusions, on the onset of plastic deformation in otherwise defect-free solids was still lacking. In this work, atomistic simulations were applied to study the role of vacancies in the inception of plasticity in metals. In particular, the effect of single vacancy as well as different vacancy distributions on the onset of plastic deformation in Ni single crystal during the nano-indentation test was explored. The combined effect of vacancy concentration and temperature on the onset of plasticity was also studied. The increase in vacancy concentration typically results in a decrease of load at the onset of plasticity. However, it was found that this was not always the case, and a particular location of one vacancy could be more important for the onset of plasticity than the higher total number of vacancies distributed in the crystal. It was also found that at higher temperatures, the effect of vacancy concentration on the load at the onset of plasticity was less pronounced than at low temperature.

Effects of Vacancies on the Onset of Plasticity in Metals - an Atomistic Simulation Study. I.Salehinia, S.N.Medyanik: Metallurgical and Materials Transactions A, 2011, 42[13], 3868-74