Rhenium effect on bend properties at liquid nitrogen temperature in single-crystal molybdenum

Abstract

With the aim of improving the low temperature strength and ductility of single-crystal molybdenum, single-crystal molybdenum-rhenium alloys were prepared by means of secondary recrystallization. Then the bend properties of these crystals were evaluated at liquid nitrogen temperature. The results can be summarized as follows. 1. (1) The yield strength decreased gradually as the rhenium content increased to 10 mass%. 2. (2) The fracture strength of as-heated crystals increased and showed a maximum at a rhenium content of 3–7 mass%. In contrast, the fracture strength of carburized crystals did not clearly show a maximum, though the absolute value of the strength of carburized crystals was generally higher than that of as-heated crystals. 3. (3) The bend angle showed a maximum at a rhenium content of 5–7 mass% irrespective of carbon content. The ductility of the crystals was generally improved by adding carbon. 4. (4) The fractography of crystals containing 3–7 mass% rhenium was similar to that of pure Mo, whilst a crack generated at one of the massive island grains in the crystal with 10 mass% rhenium.