Effects of rhenium and carbon additions on the fracture strength, ductility and fracture mode of powder-metallurgy molybdenum at low temperatures were investigated.
The results are summarized as follows:
(1) Low-temperature fracture strength of molybdenum indicated a maximum at 10 mass% rhenium. Rhenium addition enhanced both intergranular and transgranular fracture strengths. Carbon addition further enhanced the intergranular fracture strength in addition to the rhenium effect.
(2) Low-temperature ductility of molybdenum seemed to indicate a maximum at 10-13 mass% rhenium or more. This result is due to the lowering of yield strength as well as the increase of fracture strength. Further improvement of ductility by the carbon addition is due to the increase of intergranular fracture strength.
(3) The present results support the “rhenium effect” reported by Klopp et al. and Lundberg et al. Molybdenum containing 13 mass% rhenium and 30 mass ppm carbon indicated a certain amount of ductility even at a temperature as low as −196°C.