Investigations of orientation and length scale effects on micromechanical responses in polycrystalline zirconium using spherical nanoindentation

Siddhartha Pathak, Surya R. Kalidindi, Nathan A. Mara
2016 Scripta Materialia  
Here we investigate the elastic and plastic anisotropy of hexagonal materialsas a function of crystal orientation using a high-throughput approach (spherical nanoindentation). Using high purity zirconium as a specific example, we demonstrate the differences in indentation moduli, indentation yield strengths and indentation post-elastic hardening rates over multiple grain orientations. These results are validated against bulk single crystal measurements, as well as data from cubic materials. By
more » ... arying the indenter size (radius), we are also able to demonstrate indentation size effects in © 2015. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ Scripta Materialia 2 hexagonal materials, including possible signatures of strain hardening due to twin formation in the nanoindentation stress-strain curves. Text: Nanomechanical testing techniques, such as nanoindentation [1-3], micropillar compression and tension [4, 5], as well as three point bend and cantilever bend techniques [6-8], have been used for the past couple of decades to probe small volumes of material of the order of 1 μm 3 or smaller. In techniques other than nanoindentation, preparation of miniaturized tensile and compression samples is typically carried out in bulk materials using Focused Ion Beam (FIB) milling, a time consuming technique that runs the risk of ion beam damage to the sample[9, 10]. Nanoindentation, on the other hand, provides copious amounts of mechanical data from extremely small volumes of material while only requiring a flat polished surface[11] . Much work has also been carried out over the past few years to obtain stress-strain curves using a spherical nanoindentation approach [2, [11] [12] [13] . This technique can transform the raw loaddisplacement data into meaningful indentation stress-strain curves that capture the local loading and unloading elastic moduli, local indentation yield strengths, and post-yield strain hardening behavior.As such, spherical nanoindentation represents a highthroughput technique that can amass enormous amounts of grain-level data from one polycrystalline sample. Early work utilizing this technique focused largely on orientation dependent local (grain-scale) mechanical responses in relatively low anisotropy cubic systems such as
doi:10.1016/j.scriptamat.2015.10.035 fatcat:6de3stdbuffflfx77xidbsqkqu