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Published online by Cambridge University Press: 26 February 2011
We present results of comparative studies of the dislocation properties and the mechanical behavior for a class of intermetallic alloys based on platinum group metals (PGM) which are being developed for ultra-high temperature applications: Ir3X and Rh3X (where X = Ti, Zr, Hf, V, Nb, Ta). For the analysis of dislocation structure and mobility, we employ a combined approach based on accurate first-principles calculations of the shear energetics and the modified semi-discrete 2D Peierls-Nabarro model with an ab-initio parametrization of the restoring forces. Based on our analysis of dislocation structure and mobility, we provide predictions of temperature yield stress behavior of PGM-based intermetallics, show that their dislocation properties are closely connected with features of the electronic structure and the L12 → D019 structural stability, and demonstrate the dramatic difference in dislocation structure and the mechanical behavior between PGM alloys with IVA and VA group elements.