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[Display omitted] Heterostructured metals possess superior mechanical properties exceeding the prediction by the rule-of-mixtures. However, it remains a challenge to understand the key microstructural factor that controls the extra work hardening. Here aided by a newly developed mechanism-based plasticity model that incorporates the constitutive law of the back stress induced by zone-scale deformation heterogeneity, we reveal that the hetero-zone boundary affected region (Hbar) plays the key role in controlling the synergistic mechanical responses of heterostructure. Specifically, the Hbar, characterized by high strain gradient with a constant characteristic width, is formed to coordinate inter-zone deformation heterogeneity. The extra work hardening originates primarily in the Hbar, where the accumulation of geometrically necessary dislocations develops back stress and forest hardening. Importantly, the extra work hardening increases proportionally with Hbar volume fraction, and the best strength-ductility combination is reached when Hbar approaches saturation. In addition, the influences of zone configuration, mechanical incompatibility, and zone volume fraction on Hbar effect are analyzed, which sheds light on potential strategies to enhance the Hbar effect for optimizing strength-ductility combination. [ABSTRACT FROM AUTHOR]

Abstract: The effects and determining factors of substitutional defects on thermal conductivity (k) have been studied by introducing Hf4+ (96% heavier than, but a similar size to, Zr4+) and Ce4+ (21% larger and 50% heavier), to replace Zr4+ on the B site of La2Zr2O7 pyrochlores. La2(Zr1− x Ce x )2O7, exhibits a flatter k–T curve and a dramatically reduced high-temperature plateau k min. This is because the size rather than the mass difference between guest and host ions determines the flatness of k–T curves, whereas the absolute mass and size values of a dopant – particularly the latter – determine the plateau k min, as k min is proportional to the square root of the ratio of the elastic modulus E to the average atomic mass. Further, larger guest ion tends to effectively weaken a bond that shows ionic character and thus reduces E. The insights gained into the high-temperature plateau regime provide guidelines for the design and selection of a low-k material at high temperatures. [Copyright &y& Elsevier]

Abstract: The evolution of structure and thermal conductivity (k) has been studied for a range of Y–La2Zr2O7 solid solutions. Within the pyrochlore range (x <0.40) Y3+ solely substitutes for La3+ below a critical composition factor (x =0.15), above which it substitutes for both La3+ and the Zr4+. A glass-like k, approaching the amorphous limit, is observed within a certain composition range (0.20⩽ x <0.40). The glass-like k behaviour is attributed to a phonon localization effect that arises from small and weakly bound Y3+ cations (rattlers) oscillating locally and independently in oversized anionic cages [(La/Y)O8]. The ultralow and glassy k makes Y3+-doped La2Zr2O7 pyrochlores promising candidate materials for high temperature thermal barrier coating topcoats. [Copyright &y& Elsevier]