Breakdown of the superplastic deformation behavior of heterogeneous nanomaterials at small length scales

Figures & data

Figure 1. Microstructure of the investigated alloy Zn-22% Al: (a) SEM image; (b) Bright field STEM image.

Figure 2. Nanoindentation creep and micropillar strain rate jump tests at room temperatures: (a) Evaluation of the strain rate sensitivity from nanoindentation creep tests ($h_{sc}$=1200 µm); (b) Evaluation of the strain rate sensitivity from micropillar strain rate jump tests ($D$=3 µm); (c) Evolution of the strain rate sensitivity with indentation depth; (d) Strain rate sensitivity as a function of the micropillar volume.

Figure 3. Stress-strain behavior and deformed microstructure for exemplary micropillar strain rate jump tests: (a - c) $D$=3 µm ($V>V_c$); (d – f) $D$=1 µm ($V<V_c$).

Figure 4: Deformed microstructure and proposed model for the observed size effect of superplastic flow (for full details the reader is referred to section 3.3): (a) STEM dark field image for a deformed micropillar showing no size effect ($V>V_c$); (b) STEM dark field image for a deformed micropillar exhibiting a size effect ($V<V_c$); (c) Schematics illustrating the origin of the size dependent ductility, as a breakdown of the coupling between boundary sliding and intracrystalline dislocation plasticity for small specimen dimensions.