Thermodynamic properties of coherent interfaces in f.c.c.-based Ag-Al alloys: A first-principles study

Journal Article · Tue Mar 14 04:00:00 EST 2000 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(99)00412-7· OSTI ID:20026641

Asta, M; Hoyt, J J

The thermodynamic properties of coherent interphase boundaries (IPBs) between the Al-rich-matrix and Guinier-Preston-zone (GP-zone) precipitate phases in Ag-Al are studied from first principles. The cluster-variation-method (CVM), with effective-cluster-interaction (ECI) parameters derived from the results of ab initio total energy calculations, is used to compute the interfacial free energies ({gamma}) and composition profiles of flat {l_brace}111{r_brace} and {l_brace}100{r_brace} IPBs as a function of temperature (T). The calculated values of {gamma} increase monotonically from zero to 35 (37)mJ/M{sup 2} for {l_brace}111{r_brace}({l_brace}100{r_brace}) IPBs as T is lowered from the critical temperature (calculated to be 760 K) to 450 K. Monte-Carlo simulations, based on the same set of ECIs used in the CVM work, have been performed to compute GP-zone morphologies at 450 K. Simulated precipitate shapes are found to be anisotropic, consistent with experimental observations. The CVM is used also to compute the gradient coefficient ({kappa}) in the Cahn-Hilliard coarse-grained free energy. Calculated values of {kappa} are found to display non-negligible concentration and temperature dependencies, in contrast to the predictions of regular-solution theory.

• Research Organization: Sandia National Lab., Livermore, CA (US)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 20026641
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 5 Vol. 48; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
ELECTRONIC STRUCTURE
FREE ENERGY
INTERFACES
MICROSTRUCTURE
MONTE CARLO METHOD
PRECIPITATION
SILVER ALLOYS
SIMULATION
THERMODYNAMICS