Effect of coherency strains on phase separation in the AlN-Al[sub 2]OC pseudobinary system

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1993.tb03962.x· OSTI ID:5727183

Chen, Jong; Tian, Qiang; Virkar, A V ^[1]

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1. Univ. of Utah, Salt Lake City, UT (United States). Dept. of Materials Science and Engineering

AlN and Al[sub 2]OC, both of 2H structure, form a homogeneous solid solution at elevated temperatures. Annealing at lower temperatures leads to the formation of two solid solutions, one AlN-rich and the other Al[sub 2]OC-rich. Samples of near equimolar composition form disk-shaped precipitates upon annealing at temperatures below [approximately]1900 C. In the present work, samples of several compositions were fabricated by hot-pressing mixtures of AlN, Al[sub 4]C[sub 3] and Al[sub 2]O[sub 3]. Lattice parameters of the resulting solid solutions were measured by X-ray diffraction. Samples of an equimolar composition were annealed at 1500 C for various periods of time up to a maximum of 512 h. Disk-shaped precipitates with their axes along the [0001] direction were initially coherent. In the coherent stage, the a lattice parameters of the precipitate and the matrix were identical because of coherent fitting of lattice planes. The shape of the precipitates and their orientation were in accord with predictions and their orientation were in accord with predictions based on theoretical calculations of coherency strain energy. Using the experimentally measured values of the aspect ratios, the precipitate/matrix interfacial energy for coherent precipitates was estimated to be on the order of a few mJ/m[sup 2]. Long-term annealing led to the loss of coherency as manifested by the formation of interface dislocations.

• DOE Contract Number: FG02-87ER45286; FG03-93ER45482
• OSTI ID: 5727183
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 76:10; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALUMINIUM CARBIDES
ALUMINIUM COMPOUNDS
ALUMINIUM NITRIDES
ANNEALING
CARBIDES
CARBON COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DISLOCATIONS
HEAT TREATMENTS
LATTICE PARAMETERS
LINE DEFECTS
NITRIDES
NITROGEN COMPOUNDS
PHASE TRANSFORMATIONS
PNICTIDES
STRAINS