• PDF / 450,926 Bytes
• 5 Pages / 594 x 774 pts Page_size
• 45 Downloads / 160 Views

DOWNLOAD

REPORT

---

[91

where PSE = density of the solidified eutectic mixture, vo = specific volume of the 0-phase at the eutectic temperature, v, = specific volume of the primary solidified phase in equilibrium with the 0-phase at the eutectic temperature, and fo = weight fraction of the 0-phase in the solidified eutectic mixture. The compositions of the equilibrium phases in the eutectic mixture, as given by Murray, 4 were used to compute fo; v, was computed by using the lattice parameter given by Eq. [3] with X = 2.48 at. pct Cu and T = 548.2 °C. By this method, Pse was determined as 3.409 g . cm -3 (Figure 1). For the density of the liquid, we have analyzed the data given by Gebhardt et al. 2 and Edwards s separately. Gebhardt et al. z measured the density of pure aluminum and seven binary A1-Cu alloys in the range of 650 -< T -< 900 °C and 0 -< Cc - 23 wt pct Cu. Their data were 'fit' according to vL = 0.3970 - 4.5322 × 10-3CL + 4.0924 × 10-ST + 1.1078 × IO-6CLT + 2.7475 x 10-5C~ [10] Edwards 8 measured the density of only three alloys in the range of 700 -< T -< 900 °C and 0 -< CL --- 30 wt pct Cu. His data resulted in vL = 0.3857 - 2.8326 × 10-3CL -t- 5.0946 x 10-ST - 5.3004 x 10-TCLT + 7.7031 x 10-7C~.

PL = 2.3585 + 2.1685 × IO-ZCL + 7.2914 × 10-5C,2

- 7 . 2 3 5 1 × 10-7C~

[12]

and PL = 2.3846 + 0.0190CL + 1.2411 × 10-4C~ + 1.8162 × 10-6C3L

[13]

with PL in g • cm -3 and CL in wt pct Cu. Equation [12] corresponds to the data of Gebhardt et al. 2 and Eq. [ 13] corresponds to that of Edwards. 8 We recommend Eq. [12] rather than Eq. [13] because Gebhardt et al. 2 used AI and Cu of purities higher than those used by Edwards. s Even so, the two equations differ at the most by only 0.08 g • cm -3. Equation [13] is merely given to add credence to the results generated from the data of Gebhardt et al. 2 The density of the solid during solidification (Ps) and the density of the eutectic-solid in this work compare well with the values of Mehrabian et al.,~ even though they did not indicate the method for computing Pse. Moreover, the density of the eutectic liquid (PLE) of this work is approximately 0.08 g • cm -3 lower than that of Mehrabian et al., l if the results based upon the data of Gebhardt et al. 2 are selected. This work has been funded in part by grants from NASAMicrogravity Science and Applications Division and the Alcoa Foundation.

REFERENCES 1. R. Mehrabian, M. A. Keane, and M. C. Flemings: Metall. Trans., 1970, vol. 1, pp. 1209-20. 2. E. Gebhardt, M. Becker, and S. Dorner: Aluminum, 1955, vol. 31, pp. 315-21. 3. E.C. Ellwbod and J. M. Silcock: Journal of Institute of Metals, 1948, vol. 74, pp. 457-67. 4. J.L. Murray: International Metals Review, 1985, vol. 30, pp. 211-14. 5. M.C. Flemings: Solidification Processing, McGraw-Hill, New York, NY, 1974, p. 34. 6. L. E Mondolfo: Aluminum Alloys: Structure and Properties, Butterworths, London, 1976, pp. 62-63. 7. S.K. Seshadri and D. B. Downie: Metal Science, Dec. 1979, vol. 13, No. 12, pp. 696-98. 8. J. D. Edwards: Chemical and Metallurgical Engineering, 1921, vol. 25, p.