HfCo2 Laves phase intermetallics - part I: solubility limits and defect mechanisms

Solubility limits and constitutional defects in Laves phase intermetallics are investigated with the C15 HfCo2 system. Several binary alloy compositio ns based on HfCo2 are characterized by optical and scanning electron micros copy (SEM), electron microprobe analysis (EPMA), X-ray diffraction (XRD), a nd density measurements. Rietveld refinements of XRD scans are used to dete rmine lattice constants, anisotropic strain parameters, and atomic occupanc ies. Compositional trends are compared against predicted or calculated tren ds due to an anti-site substitution or vacancy defect mechanism. Geometric models and atomic size factors are used to establish solubility limits and to give insight into defect mechanisms. Results from various, complementary experiments are consistent with anti-site substitutions on both sides of H fCo2 stoichiometry. (C) 2001 Elsevier Science Ltd. All rights reserved.