This study investigates the directional recrystallization behavior of Ni based oxide dispersion strengthened (ODS) alloy according to the zone annealing velocity. The zone annealing temperature is set as 1390°C, while the zone velocities are set as 2.5, 4, 6, and 10 cm/h, respectively. The initial microstructure observation of the as-extruded sample shows equiaxed grains of random orientation, with an average grain size of 530 nm. On the other hand, the zone annealed samples show a large deviation in grain size depending on the zone velocities. In particular, grains with a size of several millimeters are observed at 2.5-cm/h zone velocity. It is also found that the preferred orientation varies with the zone annealing velocity. On the basis of these results, this study discusses the role of zone velocities in the directional recrystallization of Ni base ODS alloy.

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• Directional recrystallisation processing: a review
  Chao Yang, Ian Baker
  International Materials Reviews.2021; 66(4): 256.     CrossRef

In the present work, we use multiwall carbon nanotubes (MWCNT) as the starting material for the fabrication of sintered carbon steel. A comparison is made with conventionally sintered carbon steel, where graphite is used as the starting material. Milling is performed using a horizontal mill sintered in a vacuum furnace. We analyze the grain size, number of pores, X-ray diffraction patterns, and microstructure. Changes in the physical properties are determined by using the Archimedes method and Vickers hardness measurements. The result shows that the use of MWCNTs instead of graphite significantly reduces the size and volume of the pores as well as the grain size after sintering. The addition of Y₂O₃.to the Fe-MWCNT samples further inhibits the growth of grains.