Nanomechanical Testing Journal Club

High-Throughput Nanoindentation for Statistical and Spatial Property Determination

by Eric Hintsala, Ude Hangen, and Douglas D. Stauffer.

JOM, 2018, 70, pp. 494–503

This paper highlights an accelerated nanoindentation technique that is at least two orders of magnitude faster than standard quasi-static indentation testing. Large data sets and quantitative property maps, especially when used in conjunction with correlated techniques characterizing the structure, provide detailed information on small-scale regions of significant industrial importance that are not easily tested on the bulk scale, such as welds, fine grain and phase structures, composites, and interfaces.

Standard nanoindentation tests are ‘‘high throughput’’ compared to nearly all other mechanical tests, such as tension or compression. However, the typical rates of tens of tests per hour can be significantly improved. These higher testing rates enable otherwise impractical studies requiring several thousands of indents, such as high-resolution property mapping and detailed statistical studies. The authors explain how care must be taken to avoid systematic errors in the measurement, including choosing of the indentation depth/spacing to avoid overlap of plastic zones, pileup, and influence of neighboring microstructural features in the material being tested. Furthermore, since fast loading rates are required, the strain rate sensitivity must also be considered. A review of these effects is given, with the emphasis placed on making complimentary standard nanoindentation measurements to address these issues. Experimental applications of the technique, including mapping of welds, microstructures, and composites with varying length scales, along with studying the effect of surface roughness on nominally homogeneous specimens, is also detailed.