Influence of gravity on the dispersoids during the melting of an oxide dispersion-strengthened alloy (INCONEL MA754)
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Influence of Gravity on the Dispersoids during the Melting of an Oxide Dispersion-Strengthened Alloy (INCONEL MA754) A.M. TISSIER and J.K. TIEN Oxide dispersion-strengthened (ODS) alloys show promise as a new class of high-temperature materials. Up to now, they are generally produced by mechanical alloying, which avoids segregation and produces a fine and uniform dispersion of oxide particles. In order to explore the feasibility of a castable ODS alloy, the present research studies the influence of gravity on the dispersoids in the melted alloy. If gravity is the major contributor to the inhomogeneity of the dispersion of oxides, it would be advantageous to design a melting process in a weightless environment. For this study, INCONEL* alloy MA754 was used. *INCONEL is a trademark of Inco Alloys International, Inc., Huntington, WV.
The authors would like to thank Professor W. Kurz and Dr. A. Hoadley, from the Ecole Polytechnique Frdrrale de Lausanne, Switzerland, for reading the manuscript and for providing many useful comments. REFERENCES 1. R. Viskanta and C. Beckermann: Mathematical Modeling of Solidification, Proc. Symp. on Interdisciplinary Issues in Materials Processing and Manufacturing, ASME, Boston, MA, 1987. 2. M. Rappaz: Int. Mater. Rev., 1989, no. 194, pp. 93-123. 3. A.B. Crowley: Int. J. Heat Mass Transfer, 1978, vol. 21, pp. 215-19. 4. K. Morgan, R.W. Lewis, and O. Zienkiewicz: Int. J. Numer. Method Eng., 1978, vol. 12, pp. 1191-95. 5. W.D. Bennon and F.P. Incropera: Int. J. Heat Mass Transfer, 1987, vol. 20, pp. 2161-70. 6. W.D. Bennon and F.P. Incropera: Int. J. Heat Mass Transfer, 1987, vol. 20, pp. 2171-87. 7. C. Beckermann and R. Viskanta: Phys. Chem. Hydrodyn., 1988, vol. 10, pp. 195-213. 8. W. Kurz and D.J. Fisher: Fundamentals of Solidification, Trans Tech Publications, Aedermannsdorf, Switzerland, 1989. 9. V.R. Voller and C. Prakash: Int. J. Heat Mass Transfer, 1987, vol. 30, pp. 1709-20. 10. K. Kubo and R.D. Pehlke: Metall. Trans. B, 1985, vol. 16B, pp. 359-66. 11. V.R. Voller, A.D. Brent, and C. Prakash: Int. J. Heat Mass Transfer, 1989, vol. 32, pp. 1719-31.
The nominal composition of the alloy is given in Table I. Presently, MA754 is used in air and space applications such as gas turbine vanes and blades. "-4j Three mechanically alloyed specimens of MA754 were melted, under vacuum, in a high-frequency induction furnace. The melting point of INCONEL MA754 is 1400 ~ The first specimen was maintained at 1425 ~ for more than 4 hours, and then the power was turned off. A second specimen underwent directional solidification at 1500 ~ and 6.5 Pa. The process included 30 minutes of complete melting and withdrawal for 4 hours. For this and a third sample, drops of liquid alloy were ejected from the crucible as soon as the alloy began melting. Because of this, the power was turned off for the third sample, as soon as some drops were thrown out. A fourth sample was melted (1405 ~ for 2.5 hours) in a furnace under atmospheric pressure. Quartz, which has a density of 2.65, had been melted previously
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