Critical-point wetting at the metastable chemical binodal in undercooled Fe-Cu alloys
- Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering
Complementary results of differential thermal analysis and microstructural examination on Fe-Cu alloys provide the first evidence for critical-point wetting occurring at a completely metastable miscibility gap. The perfect wetting conditions hold for a composition range of 50--65 at.% Fe in the vicinity of the critical concentration. For samples encased with a glass slag, the Cu-rich liquid completely wets the glass upon undercooling to the metastable miscibility gap. In the perfect-wetting range, the metastable homogeneous liquid phase exhibited phase separation without undercooling below the chemical binodal. At deep undercooling, solidification of alloys with phase separated liquids results in a coarse scaled two-phase microstructure. In contrast, the homogeneous liquid phase of samples with compositions outside the perfect wetting range did undercool below the equilibrium onset of the metastable phase separation reaction. The phase separation in these samples occurred on a much finer scale. For samples without a glass encasement and thus in the presence of the Al{sub 2}O{sub 3} crucible and an iron oxide layer, perfect wetting occurred near the consolute point on both sides of the metastable miscibility gap. This demonstrates that critical-point wetting is independent of the surface environment, but the wetting phase selected is surface sensitive.
- OSTI ID:
- 684401
- Journal Information:
- Acta Materialia, Vol. 47, Issue 10; Other Information: PBD: 10 Aug 1999
- Country of Publication:
- United States
- Language:
- English
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