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Precipitation in Powder Metallurgy, Nickel Base Superalloys: Review of Modeling Approach and Formulation of Engineering (Postprint)

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Journal Article

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Air Force Research Laboratory, Materials and Manufacturing Directorate Wright Patterson Air Force Base

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Methods for determining the various thermodynamic and kinetic parameters required for the modeling of precipitation in powder-metallurgy PM, nickel-base superalloys are summarized. These parameters comprise the composition of the phase, the solvus temperatureequilibrium solvus approach curve, the free energy G associated with the decomposition of the matrix to form , the interfacial energy , and an effective diffusivity for use in nucleation, growth, and coarsening calculations. Techniques to obtain the material data include phase extraction for the average composition of and heat-treatmentquantitative metallography for a two-parameter fit of the solvus approach curve. With regard to G, two methods, one based on the instantaneous composition of the and phases and the other on the enthalpy of transformation and the solvus temperature, are summarized. It is shown that the interfacial energy can be determined from the nucleation-onset temperature as indicated by on-cooling specific-heat measurements

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