Grain refinement in undercooled nickel

Journal Article · Mon May 15 04:00:00 EDT 1995 · Scripta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-716X(94)00029-H· OSTI ID:69647

Leung, K K; Chiu, C P; Kui, H W ^[1]

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1. Chinese Univ. of Hong Kong, Shatin (Hong Kong). Dept. of Physics

In this paper, the microstructures of undercooled Ni that solidified at various initial bulk undercoolings are examined in detail in order to understand the mechanism of grain refinement in metallic systems. Molten Ni contracts on solidification. In the experiment, since it was covered by molten glass flux, upon crystallization cavities had to form to accommodate the rapid volume change if the undercooled specimen remained in contact with the glass flux, which could not flow so readily. The adhesiveness between Ni and glass flux was confirmed by removing them from a furnace after the whole system had been cooled down to room temperature. Furthermore, it was clear from the micrographs that after a cavity had formed, it did not collapse. It can therefore be concluded that smaller grains are found to concentrate near the void along the minor axis. At still higher undercoolings, the effect was so violent that the voids took irregular shapes. Again, the grains near the cavity are somewhat smaller than those further away. Accordingly, the authors conclude that grain refinement in undercooled Ni was brought about by dynamic nucleation as the cavities formed.

• OSTI ID: 69647
• Journal Information: Scripta Metallurgica et Materialia, Journal Name: Scripta Metallurgica et Materialia Journal Issue: 10 Vol. 32; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTALLIZATION
GRAIN REFINEMENT
GRAIN SIZE
LIQUID METALS
MICROSTRUCTURE
NICKEL
NUCLEATION
OPTICAL MICROSCOPY
SCANNING ELECTRON MICROSCOPY
STRESSES