The time-dependent characteristics of incipient plasticity in Ni3Al during nano-indentation in the sub-critical load regime were investigated statistically. The waiting time for incipient plasticity to occur at constant load was found to follow a Poisson-like distribution, with the peak shifting toward zero holding time as the load increased and eventually becoming an exponential distribution when the load was close to a critical value. The observed distribution of the strain burst waiting time at loads smaller than the critical value was inconsistent with the picture in which dislocations nucleated homogeneously out of the perfect crystal. The kinetics for the occurrence of strain burst in this case was thought to be governed by the accumulative growth of nucleation precursors.

Time-Dependent Incipient Plasticity in Ni3Al as Observed in Nanoindentation. Wo, P.C., Zuo, L., Ngan, A.H.W.: Journal of Materials Research, 2005, 20[2], 489-95