Concerning Sigma-Phase in Molybdenum-Rhenium Alloys

Aging effects on microstructural and mechanical properties of select refractory metal alloys for space-reactor applications

“…3 [12]. However, this contradicts earlier work [16] that showed an extension of the r phase field to temperatures below 1398 K. The morphology of the v-phase and its direct one-to-one orientation relationship with the aMo solid solution are shown in more detail in the TEM images of Fig. 6.…”

“…5(a)). Two-phase structures were also reported by Shields [15] following 1 h anneal of Mo-47.5Re at 1773 K, with traces of the r-phase remaining following 2.7 h annealing at 1873 K having also been reported [16]. Aging Mo-47.5Re at 1398 K produced a nearly continuous precipitation of the r-phase along grain boundaries (Fig.…”

Microstructural and mechanical property changes with aging of Mo–41Re and Mo–47.5Re alloys

“…6. The Mo-Re diagram of [26] shows the Mo-47.5Re alloy lying outside the aMo + r phase field, contrary to this and other existing work. The presence of the r phase in the 1773 K annealed material and the resulting tie-line compositions suggest that the boundary of the Re solubility in the aMo phase is of a leaner Re concentration than shown in either diagrams.…”

Thermodynamic assessment of the Mo–Re binary system

“…This temperature is within the suggested temperature range between 1373 K and 1423 K [7]. Previous work indicates that the is an undesirable phase [4] The calculated phase diagram provides a route for removing the by long time annealing at temperatures below 1375 K (1119 • C).…”

“…Both and phases are expected to be brittle due to their complex structure. In fact, the presence of the phase has received much attention because its brittleness reduces the low-temperature ductility and hightemperature strength of the Mo-Re alloys [4]. Despite the broad applications of the Mo-Re alloys, part of the phase diagram remains unclear [5].…”