1990 年 17 巻 2 号 p. 219-222
A molybdenum single crystal with a large-scale and optional shape was easily obtained by the secondary recrystallization method. There are two fundamental factors for producing single crystal. The one is the presence of dis- persed second phases such as CaO and MgO, the other is the presensed of strong primary texture with fine-grained structure. A certain amount of CaO and MgO is effective as inhibitors on the grain growth behavior of worked molybdenum : initially restraining the normal grain growth by precipitation of CaO or MgO at primary recrystal- lized grain boundaries and conversely permitting the abnormal grain growth by decomposing them to single element at higher temperatures. The effect of initial grain size on the secondary grain growth behavior is important. In the case where the initial grain size was smaller than 50urn, a uniform and fine-grained recrystallized structure was obtained after annealed at 1500℃, whilst an abnormal grain growth occurred after annealed at 2000℃.