Inhibited coarsening of solid-liquid microstructures in spray casting at high volume fractions of solid

Journal Article · Tue Aug 01 04:00:00 EDT 1995 · Acta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-7151(94)00448-Q· OSTI ID:100617

Annavarapu, S; Doherty, R D ^[1]

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1. Drexel Univ., Philadelphia, PA (United States). Dept. of Materials Engineering

Experimental studies on coarsening in fine grained solid-liquid microstructures at high volume fractions of solid (f{sub s}) have been carried out to determine if inhibited coarsening under these circumstances could account for the anomalous fine cell sizes observed in spray castings. The materials investigated included a chill-cast dendritic binary alloy of Al-Cu, two spray cast alloys-AA2014 and Cu-Ti, whose grain size was the segregate spacing, and a d.c.-cast alloy Al-4.5 wt% Cu-1.5 wt% Mg in both coarse-grain and grain-refined conditions. The observed segregate spacings after coarsening were smaller than that predicted by empirical correlations of dendrite arm spacing and freezing time. In all cases, the coarsening was found to become slower as the temperature was reduced and f{sub s} increased. Conventional coarsening theories and experiments predict the opposite, i.e. faster coarsening at higher volume fractions of solid. Two additional coarsening models were developed for the grain growth at high volume fractions of solid by processes whose rates are limited by migration of liquid at grain boundaries as liquid films on 2-grain surfaces or liquid rods on 3-grain triple points. In both models, the conventional diffusion-limited t{sup 1/3} coarsening law was reproduced, but the rate constant K contained the term 1/1 {minus} f{sub s} and so also predicted accelerated coarsening as f{sub s} {yields} 1.

• OSTI ID: 100617
• Journal Information: Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 8 Vol. 43; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
COPPER ALLOYS
DENDRITES
GRAIN BOUNDARIES
GRAIN GROWTH
GRAIN REFINEMENT
GRAIN SIZE
LIQUIDS
MAGNESIUM ALLOYS
MICROSTRUCTURE
SOLIDIFICATION
SOLIDS
TEMPERATURE DEPENDENCE
TITANIUM ALLOYS