STRUCTURAL IDENTIFICATION OF PHASES IN Mo-Re ALLOYS WITHIN THE RANGE FROM 5 TO 95 Re

摘要

Molybdenum-rhenium alloys are particularly more advantageous than other refractory alloys for aerospace and energy systems applications, because of availability and high-temperature strength levels. Besides the solid solubility found in binary Mo-Re alloys, the existance of sigma and chi-phases has received much attention because of the important effects that the formation of these phases has on the properties of the industrial alloys. This article deals with the quantitative identification of those phases as formed under nearly-equilibrium cooling of the powder-sintered alloys. Eighteen different compositions were prepared among the range from 5 to 95% of Re in Mo, by sintering of Mo-Re powder mixtures at 1750°C under protecting Ar-H{sub}2 atmosphere. The relatively fast cooling rate of the alloys resulted in a modification of the phase stability zones at room temperature; hence sigma and chi-phases were formed at various compositions in the studied range. The satbility zones and relative amount of all phases were determined by means of quantitative X-ray diffraction analysis of the various samples.