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Mo-Re alloys containing between 5 and 47.5 wt pct Re were fabricated from Mo and Mo-Re powders by sintering and hot radial forging. The mechanical properties of as-forged, stress-relieved, and recrystallized specimens were examined. Up to a concentration of 41 wt pct Re. the Charpy ductileto-brittle transition temperature decreased monotonically with increasing rhenium concentration. Consistent with this, bend angles for fracture at T = -100 °C increased monotonically with increasing rhenium concentration. Between 10 and 41 wt pct rhenium, the room-temperature tensile ductility of recrystallized Mo-Re remained nearly constant with values on the order of 35 to 45 pct. This result differs from the low ductility values observed previously by Lundberg (1997) for compositions on either side of Mo-13 wt pct Re.
I. INTRODUCTION
GEACH and Hughes,[1] in 1955, were the first to demonstrate the remarkable effect of rhenium on improving the room-temperature ductility of molybdenum. The "Re effect" was substantiated soon afterward by Jaffee et al.[2] More recently, Agnew and Leonhardt[3] reviewed the literature for Mo-Re and carried out experiments illustrating the important role of twinning tor the high ductility of Mo-47.5 wt pct Re at temperatures as low as -180 °C.
An important factor limiting the application of Mo-Re alloys is the scarcity and high price of rhenium. If the rhenium concentration could be significantly reduced below the typical 40 to 50 wt pct. more applications would likely emerge. Interestingly, according to Lundberg et al.,[4,5] the room-temperature tensile elongation of Mo-Re appears to have a pronounced maximum, approximately 50 pct, for rhenium concentrations between 10 and 15 wt pct. This might suggest Mo-13 wt pct Re alloys as a suitable substitute for the more expensive Mo-47.5 wt pct Re. The main motivation for the present work is to reappraise Lundberg et al.'s ductility maximum for Mo-13 wt pct Re by examining Mo-Re alloys with concentrations ranging from 5 to 47.5 wt pct Re. In addition, low-temperature and high strain rate (impact) tests were carried out. A further motivation to revisit the Re effect in molybdenum stems from the renewed interest in refractory metal suicide alloys for structural applications at ultra-high temperatures in air.[6] The successful application of these alloys requires a judicious balance between oxidation resistance at high temperatures and toughness at...