Recent nano-indentation experiments on bulk samples as well as compression tests on micro-pillars indicated that the micron-sized material volumes exhibited a first yield point that strongly depended on the sample size. Molecular dynamics simulations were carried out here in order to investigate the onset of yielding in Ni3Al nano-sized pillars. The molecular dynamics results showed that dislocation generation was from the free surfaces of the micro-pillars, when thermal vibration induces too large a local interatomic displacement. The statistical distributions of the near-surface thermal atomic displacements gathered from the Molecular dynamics simulations were used in conjunction with a survival probability model to predict the yield conditions of real-sized micro-pillars in real time-scales. The predicted results agreed fairly well with published experimental results.

Molecular Dynamics Study on Compressive Yield Strength in Ni3Al Micro-Pillars. Zuo, L., Ngan, A.H.W.: Philosophical Magazine Letters, 2006, 86[6], 355-65