Alloying to improve the properties of welded molybdenum

Tensile tests at 203 K were performed on electron-beam-welded molybdenum and molybdenum-base alloys. The effects of alloying elements, carbon, zirconium, niobium, vanadium (with or without boron) and rhenium were determined on the low-temperature ductility of weld joints. The results are related to the microstructural effects. The effects of alloying are as follows: (1) Carbon enhanced the fracture strength and improved the ductility due to the grain boundary strenthening. (2) Zr, Nb or V with boron enhanced both the yield and fracture strengths due to the grain refining, but the ductility was only slightly improved. (3) 5% Re induced a high fracture strength due to the refinement of precipitates, an exceptionally low yield strength due to the solution softening, and the ductility was substantially improved. (orig.)