| Preparation of double-layered grain structure was stuided in molybdenum (Mo) sheet. Mo powder doped with CaO and MgO (D-layer) and pure Mo powder (P-layer) were compacted at 300MPa in sequence of P-D-P and D-P-D. The compacts were sintered at 1850℃ and straight rolled by 70% reduction in thickness. Microstructures in thickness direction were observed by optical, scanning electron and transmission electron microscopies. Pole intensities were also calculated for a specific [hkl] orientation. To understand the role of dopants, i.e, CaO and MgO during annealing, P-D-P and D-P-D specimens were annealed at 1200℃ for 10hrs, at 1776℃ for 2hrs and at 1950℃ for 2hr under hydrogen atmosphere. D-layers at the surface of D-P-D specimen revealed smaller grain size than D-layer at the center of P-D-P specimen in the range of primary recrystallization (l200℃), At 1776℃, both P-D-P and D-P-D specimens showed secondary recrystallization phenomenon from the surface of specimen, At 1950℃, double-layered grain structure developed in D-P-D specimen while coarse grains formed in P-D-P specimen. |
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