Structural identification of phases in Mo–Re alloys within the range from 5 to 95% Re

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 existence of σ- and χ-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 paper 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–H2 atmosphere. The relatively fast cooling rate of the alloys resulted in a modification of the phase stability zones at room temperature; hence σ- and χ-phases were formed at various compositions in the studied range. The stability zones and relative amount of all phases were determined by means of quantitative X-ray diffraction analysis of the various samples.