Determining the activation energies and slip systems for dislocation nucleation in body-centered cubic Mo and face-centered cubic Ni single crystals

Nanoindentation tests were performed on single crystals of Mo and Ni. The critical shear stress for the first pop-in was ∼1/7 of the shear modulus in both crystals. The dependence of pop-in probability on load was understood in terms of a thermally activated dislocation nucleation process. Comparison of the activation energies suggests nucleation of full dislocations in Mo and partial dislocations in Ni. The activation energy analysis also offers information on the specific slip system on which dislocations are nucleated.