Analytical approach for pop-in and post-pop-in deformation behavior during nanoindentation: effect of solute Si in interstitial free steel

Abstract

Effect of solute atom on dislocation nucleation and subsequent elasto-plastic deformation observed in nanoindentation tests was investigated using Si-alloyed interstitial-free steel (IF). The onset shear stresses for plastic deformation τp at the first pop-in where the dislocation nucleation occur were greatly affected by the presence of solute Si irrespective of the Si content tested. The analysis of the cumulative probability of τp indicate that the dislocation nucleation occurred through heterogeneous nucleation where the nucleation sites are solute Si atoms. It has suggested that Si has ability to increase the activation energy for dislocation nucleation. The variation in the magnitude of displacement burst at the first pop-in showed that more kinetic energy of moving dislocations is dissipated by the presence of solute Si resulting in decrease of travel distance of dislocations. This trend can be explained by classical solid solution theory. The staircase yielding observed only in Si-alloyed sample indicate that the re-activation of dislocations formed at the pop-in became difficult by the solute Si.