Contrary to the dislocation-driven ‘smaller-is-stronger’ size-effect in nanocrystals, the size-dependence of strength in deformation twinning, another carrier of plasticity, still lacks universal understanding. Deformation twinning enables pseudoplastic strain of >5% in a shape memory ceramic (ZrHfO4)x (YTaO4)1−x. We use diffraction methods, microstructure analysis, and in-situ nanomechanical experiments to uncover contributing factors to the competition between twinning and slip in these submicron-sized ionic crystals, revealing power-law scaling of strength with size for both mechanisms. The significant twinning size-dependence was found to follow a superimposed power-law with exponent of -1, identical to that in metals. These findings unveil the universality of the superimposed power-law size-effect for twinning in single-crystals and provide new insights on deformability of ceramics and microstructure-driven nano-plasticity.
Bibliographical noteFunding Information:
HZ and JRG gratefully acknowledges the financial support from the U.S. Department of Basic Energy Sciences under Grant DE-SC0006599 . HG and RDJ acknowledge the support of a Vannevar Bush Faculty Fellowship, USA . EQ and JJ acknowledge support by the German Research Foundation (DFG) via a Reinhart Koselleck project (Project number 313454214).
© 2020 Elsevier Ltd
- Deformation twinning
- In-situ nanomechanics
- Shape memory ceramics