In order to clarify the fundamental factors for preparing technologically a largescale molybdenum single crystal by. means of secondary recrystallization, the effect of rolling reduction on the secondary grain growth in molybdenum sheet doped with CaO and NgO was investigated texturally and optically.
For the case where the rolling reduction was more than 60%, a uniformed and finegrained recrystallized structure was obtained after an anneal at 1500 or 1800°C, while the secondary grain growth occurred after an anneal at 2000°C and a single crystal was obtained. In contrast, for the case where the rolling reduction was less than 50%, only coarse-grained recrystallized structure was obtained after an anneal at 1500 or 1800°C. Even after an anneal at 2000°C the secondary grain growth did not occur. Consequently, a single crystal was not obtained even for a rolled sheet doped with a certain amount of CaO and/or KgO.
These behaviors can be explained in relation to the shape and size of grains obtained for primary recrystallized sheet as a result of rolling reduction.