Phase formation sequence of Cr2AlC ceramics starting from Cr-Al-C powders

The reaction process of Cr2AlC ceramics was analyzed, in which the samples were prepared for composition Cr:Al:C = 1: 121 by hot-pressing in argon in the range of 850-1450 degrees C using Cr, Al and graphite powders as the starting materials. X-ray diffraction (XRD), electron probe microanalysis (EPMA) and energy dispersive spectrum (EDS) were employed for identification of phase assembly and analysis of reaction route of the samples. The phase formation sequence of Cr2AlC was finally analyzed based on phase diagram of the Cr-Al binary system combined with the results of differential thermal analysis (DTA) and XRD. It was found that Cr5Al8, Cr2Al and Cr7C3 were the intermediate phases appearing in turn in the heating process. The amount of Cr2AlC phase was gradually increased with increase in temperature by the reaction between Cr-Al intermetallic compounds, un-reacted Cr and graphite, and it became a pure phase in the sample with disappearance of intermediate phases above 1250 degrees C. (c) 2006 Elsevier B.V. All rights reserved.