Directional Recrystallisation in Mechanically Alloyed Oxide Dispersion Strengthened Metals by Annealing in a Moving Temperature Gradient

W. Sha and H. K. D. H. Bhadeshia


The directional recrystallization behaviour of mechanically alloyed oxide dispersion-strengthened nickel- and iron-base alloys, MA760 and MA956, has been investigated by annealing in a moving temperature gradient (zone or laser annealing). The directional microstructure produced in MA760 was found to become more isotropic as the zone-annealing speed was increased. At the same time, the recrystallization front tended to become irregular with some nucleation occurring ahead of the main front as the zone-annealing speed exceeded the grain-boundary velocity. These data have been analysed theoretically. Laser-induced recrystallization has also been explored, as another method of annealing a sample in a moving temperature gradient. In the case of the iron-base MA956 alloy, recrystallization occurred directionally along the bar extrusion direction, irrespective of the laser zone-annealing direction.

Journal of Materials Science, Vol. 30, 1995, 1439-1444.

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