Oxidation of the hexagonal Zr(Cr0.4Fe0.6)2 Laves phase

The hexagonal (C14-type) Laves phase Zr(Cr0.40Fe0.60)(2) when oxidized in an open furnace was studied by X-ray diffraction and Mossbauer spectroscopy techniques. Oxidation modified part of the original Laves phase and Zr oxides, Cr oxides, alpha-Cr, (Fe, Cr) oxides, alpha-Fe and alpha-Fe2O3 appeared. The behaviour of these phases, particularly the Fe-bearing phases, is described in detail through a two stage process (stage I from 0 to similar to7 wt% 02 and stage 11 up to 22 wt% O-2). A very small amount of O-2 (stage 1) is enough to induce the formation of alpha-Fe upon oxidation, sustaining a model previously suggested for the oxidation of the Laves phases. This alpha-Fe is highly Cr-substituted. Oxidation proceeds through the increasing presence of alpha-Fe2O3 and through the structural evolution of Zr oxides (formation of monoclinic, tetragonal and cubic ZrO2). (C) 2004 Elsevier B.V. All rights reserved.