Abstract
One reason for the much higher strengths of small volumes of materials compared to their bulk counterparts is the absence of defects in the probed volumes. The present work demonstrates that the defect density gives rise to a natural length scale to the mechanical behavior. Experimentally, a nanoindentation size effect is demonstrated in single-crystal Mo, showing behavior ranging from theoretical strength to near-bulk behavior with a well-defined yielding at much lower stresses. A statistical model captures the change in nanoindentation behavior, including the wide variability of an intermediate regime between the theoretical “defect free” limit and the bulk behavior where large numbers of defects are present. A predicted scaling behavior is verified by nanoindentation experiments, using indenter radii that vary by over an order of magnitude in size.
