Nanoscale strength distribution in amorphous versus crystalline metals

TitleNanoscale strength distribution in amorphous versus crystalline metals
Publication TypeJournal Article
Year of Publication2010
AuthorsPackard, CE, Franke, O, Homer, ER, Schuh, CA
JournalJournal of Materials Research
Volume25
Issue12
Pagination2251 - 2263
Date Published2010/12//
Abstract

Low-load nanoindentation can be used to assess not only the plastic yield point, but the distribution of yield points in a material This paper reviews measurements of the so-called nanoscale strength distribution (NSD) on two classes of materials crystals and metallic glasses In each case, the yield point has a significant spread (10-50% of the mean normalized stress), but the origins of the distribution are shown to be very different in the two materials classes In crystalline materials the NSD can arise from thermal fluctuations and is attended by significant rate and temperature dependence In metallic glasses well below their glass-transition temperature, the NSD is reflective of fluctuations in the sampled structure and is not very sensitive to rate or temperature Computer simulations using shear transformation zone dynamics are used to separate the effects of thermal and structural fluctuations in metallic glasses, and support the latter as dominating the NSD of those materials at low temperatures Finally, the role of the NSD as a window on structural changes due to annealing or prior deformation is discussed as a direction for future research on metallic glasses in particular