RECRYSTALLIZATION IN THORIA DISPERSED NICKEL SHEET.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF MATERIALS SCIENCE
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Recrystallization in thoria dispersed nickel sheet was examined as a function of strain-anneal cycles employing various degrees of cold deformation followed by heat treatment at temperatures in the range 500C to 1300C. Electron transmission techniques were used for quantitative determination of the degree of recrystallization. As might be expected, the observed percentage of recrystallized material after any chosen heat treatment regime progressively increased with increasing severity of prior cold deformation in a single cycle of strain and anneal. However, the material exhibited a remarkable resistance to complete recrystallization. The most severe strain-anneal cycle employed, 80 percent cold reduction plus one hour at 1300C, could not promote more than 80 percent recrystallization. Recrystallization resistance also appeared to be fortified by successive cycles of strain and anneal. Substructure examination clearly showed the presence of a banded structure where the alternate bands of recrystallized and unrecrystallized material were aligned along the original cold rolling direction. The substructure offered no immediate explanation of the resistance to recrystallization in specific regions of the material, although it is worth noting that particle-matrix interface cavities previously proposed as grain boundary pinning points were not observed. Electron diffraction scanning of transmission specimens indicated strong grain alignment in localized regions texture, but a positive correlation with recrystallization resistance has not yet been found. Author
- Metallurgy and Metallography
- Fabrication Metallurgy