Coherent phase equilibria: Effect of composition-dependent elastic strain

Journal Article · Tue Feb 01 04:00:00 EST 1994 · Acta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-7151(94)90511-8· OSTI ID:143157

Lee, J K; Tao, Weimin ^[1]

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1. Michigan Technological Univ., Houghton, MI (United States). Dept. of Metallurgical and Materials Engineering

Recent investigations on coherent equilibria have shed much light on the nature of phase stability. For example, equilibrium phase concentrations are shown to depend on the alloy composition, and two-phase coexistence can terminate at a critical coherency strain, termed a Williams point. This work, however, presents that when lattice parameter, hence coherency strain, is taken to be a function of phase composition, Williams point can disappear, i.e. the two-phase termination occurs only at an infinite elastic strain. In particular, if lattice parameter depends linearly on phase composition following Vegard`s law, the equilibrium phase compositions are found to be independent of alloy composition, similar to the incoherent equilibrium case, but the chemical potentials vary with alloy composition, underlying breakdown of the usual Gibbs phase rule. When the analysis is extended to a binary regular solution obeying Vegard`s law, complete nature of both coherent solvus and coherent spinodal is revealed in accordance with Cahn`s prediction made a generation ago.

• DOE Contract Number: FG02-87ER45315
• OSTI ID: 143157
• Journal Information: Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 2 Vol. 42; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALLOYS
CHEMICAL COMPOSITION
ELASTICITY
MATHEMATICAL MODELS
PHASE STUDIES