Quantification of overaging hardening kinetics of aluminum alloys
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12/29/04
10:39 PM
Page 2172
Table II. Reported and Calculated Values of Lattice Parameters of Pure Ni3Al and Phase in Superalloys CMSX-2 and SRR99 Lattice Parameter (nm)
Datum Source
Ni3Al
Reported Using Eq. [9] Using Eq. [10]
0.3567[4] 0.3568 0.3631
(CMSX-2)
(SRR99)
0.3585[1] 0.3578 0.3625
0.3588 0.0002[3] 0.3586 0.3633
Theoretically, the proposed calculation method can also be used in the prediction of unconstrained lattice parameters of other ordered phases if only the chemical concentration of sublattices of the phases investigated is obtained. Fig. 1—Atomic spacing in characteristic close-packed directions AB, BC , and DC in sublattices and the lattice parameter of phase AD ag ¿ .
REFERENCES Table I. Chemical Concentration of Sublattices in Pure Ni3Al and in Phase of Superalloys CMSX-2[8] and SRR99[9] Chemical Concentration of Sublattices, At. Pct Alloying Element Ni Co Ti Cr Al W Ta
(CMSX-2)
Ni3Al
(SRR99)
Xf
Xc
Xf*
Xc*
Xf
Xc
100.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 100.00 0.00 0.00
85.00 6.00 2.00 7.00 0.00 0.00 0.00
17.00 1.50 3.00 0.00 60.50 11.50 6.50
88.97 3.41 3.31 3.41 0.80 0.10 0.00
16.90 1.00 4.80 0.20 63.10 9.20 4.80
*Xf and Xc correspond to X2il and X2i, respectively, in the equations given previously.
of the ordered phase, whereas an obvious discrepancy exists when the conventional Eq. [10] is used. Thus, as compared with Eq. [10], the derived Eq. [9] is more suitable for the calculation of lattice parameters of unconstrained L12 structured in Ni-base superalloys. Table I gives the chemical concentration of sublattices of Ni3Al and phase in superalloys CMSX-2[8] and SRR99,[9] respectively. Table II makes a comparison between the reported and calculated values in lattice parameter, respectively. The magnitudes of atomic radius of the alloying elements present in the phase are cited from Reference 10 when the related calculation is performed. The results verify the fact that the magnitude of lattice parameter of ordered phase is closely related with the atomic site occupancy and the chemical concentration of sublattices in phase. It is clear that Eqs. [9] and [10] reflect the existing geometric relationship between the weighted closest atomic spacing of alloying elements and the unconstrained lattice parameter of an ordered L12 structured phase and a disordered fcc structured phase, respectively. It is suggested that the derived Eq. [9] should be more suitable to the phase than Eq. [10], which has been widely used for the disordered fcc structure, when a sufficient number of data regarding the unconstrained lattice parameters and the chemical concentrations of sublattices of the ordered phase are available. 2172—VOLUME 35A, JULY 2004
1. P. Caron and T. Khan: Mater. Sci. Eng., 1983, vol. 61, pp. 173-84. 2. U. Brückner, A. Epishin, T. Link, and K. Dressel: Mater. Sci. Eng. A, 1998, vol. 247A, pp. 23-31. 3. R. Völkl, U. Glatzel, and M. Feller-Kniepmeier: Acta Mater., 1998, vol. 46 (12), pp. 4395
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