Solidification of binary hypoeutectic alloy matrix composite castings

Journal Article · Fri Mar 01 04:00:00 EST 1996 · Metallurgical Transactions, A

DOI:https://doi.org/10.1007/BF02648949· OSTI ID:237771

Mortensen, A; Flemings, M C ^[1]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering

The authors consider a binary hypoeutectic alloy casting which solidifies in dendritic form in an unreinforced engineering casting and seek to predict its microstructure in a metal matrix composite. They focus on the case where the reinforcement is fixed in space and fairly homogeneously distributed. The authors assume that the reinforcement does not catalyze heterogeneous nucleation of the solid. They show that the reinforcement can cause several microstructural transitions in the matrix alloy, depending on the matrix cooling rate, the width, {Lambda}, of interstices left between reinforcing elements, and the initial velocity V of the solidification front. These transitions comprise the following: (1) coalescence of dendrite arms before solidification is complete, causing solidification to proceed in the later stages of solidification with a nondendritic primary phase mapping the geometry of interstices delineated by reinforcement elements; (2) sharp reduction or elimination of microsegregation in the matrix by diffusion in the primary solid matrix phase; and (3) a transition from dendrite to cell formation, these cells featuring significant undercoolings or a nearly plane front configuration when reinforcing elements are sufficiently fine. Quantitative criteria are derived for these transitions, based on previous work on composite solidification, observations from directional solidification experiments, and current solidification theory. Theory is compared with experimental data for aluminum-copper alloys reinforced with alumina fibers and for the dendrite to cell transition using data from directional succinonitrile-acetone solidification experiments. Theory and experiment show good agreement in both systems.

• Sponsoring Organization: USDOE
• OSTI ID: 237771
• Journal Information: Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 3 Vol. 27; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACETONE
ALUMINIUM ALLOYS
ALUMINIUM OXIDES
BINARY ALLOY SYSTEMS
COMPOSITE MATERIALS
COPPER ALLOYS
CORRELATIONS
DENDRITES
DIFFUSION
FLUID FLOW
HEAT TRANSFER
INTERFACES
LIQUID METALS
MICROSTRUCTURE
NITRILES
SEGREGATION
SOLIDIFICATION
SUCCINIC ACID
VELOCITY