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Migration of Intergranular Liquid Films and Formation of Core‐Shell Grains in Sintered TiC–Ni Bonded to WC–Ni
Author(s) -
Ko Ji Yeon,
Park SinYoung,
Yoon Duk Yong,
Kang SukJoong L.
Publication year - 2004
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2004.tb07502.x
Subject(s) - materials science , nucleation , mixing (physics) , dissolution , surface energy , strain energy , core (optical fiber) , diffusion , composite material , grain boundary , metallurgy , microstructure , chemical engineering , thermodynamics , physics , quantum mechanics , finite element method , engineering
When TiC–20 wt% Ni powder mixtures are sintered at 1400°C, relatively large TiC grains possibly containing some Ni form with near‐equilibrium shapes. When these specimens are heat‐treated again at 1400°C in contact with sintered WC–20 wt% Ni pieces, the liquid films between the TiC grains in the contact region migrate against their increasing curvatures, forming (Ti,W)C solid solution behind them. These migrating liquid films reverse their directions on further heat‐treatment. As in other alloys, this liquid film migration must be driven by the coherency strain energy produced by W diffusion at the surface of the dissolving TiC grains. Shells of (Ti,W)C solid solution also form around the cores of TiC grains near the contact region, and this process is probably driven by both coherency strain energy and free energy of mixing. At some contact regions, (Ti,W)C precipitates nucleate and grow, probably driven mainly by the free energy of mixing. In powder mixtures, the formation of core‐shell grains is expected to be driven by the coherency strain energy, the free energy of mixing, and the capillary effect.