モリブデン鋳塊の延性におよぼす0.15 wt% RuとC, B複合添加の影響

抄録

As a preliminary experiment to investigate the applicability of alloy softening with platinum group metals to the ductility improvement of polycrystalline molybdenum, the effects of single additions of Ru and Pt and of complex additions of 0.15 wt% Ru and C or B on the room-temperature ductility of an electron-beam melted molybdenum ingot have been studied. The results are as follows: (1) Room-temperature hardness of the ingot was lowered by 35∼45 in Vickers hardness by the single additions of 0.1∼0.2 wt% Ru and Pt. However, these softened ingots were apt to fracture intergranularly at a low stress and displayed virtually no ductility. (2) The complex additions of 0.15 wt% Ru and a suitable amount of C or B made the ingot ductile and soft, the room-temperature hardness of which was about 30 in Vickers hardness lower than that of the unalloyed ingot. These ductile ingots could be rolled sufficiently at 1200°C as in the case of the ingots alloyed with C and B respectively, without Ru, though Ru increases the high-temperature hardness of ingot. (3) It can be concluded that alloy softening with Ru may be useful to the ductility improvement of polycrystalline molybdenum when the intergranular brittleness is suppressed.