The mechanism of porous column formation during spray forming
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P.M. Kelly: Trans. AIME, 1965, vol. 233, p. 264. M.H. Yoo: Metall. Trans. A, 1981, vol. 12A, pp. 409-18. H.P. Chu: J. Mater., 1970, vol. 5, pp. 633-42. M.A. Imam and C.M. Gilmore: Metall. Trans. A, 1979, vol. 10A, pp. 419-25. W.H. Miller, Jr., R.J. Chen, and E.A. Starke, Jr.: Metall. Trans. A, 1987, vol. 18A, pp. 1451-68. B.C. Odegard and A.W. Thompson: Metall. Trans. 1974, vol. 5, pp. 1207-13. S. Suri, P. Neeraj, G.S. Daehn, D.H. Hou, J.M. Scott, R.W. Hayes, and M.J. Mills: Mater. Sci. Eng., 1997, vols. A234–36, pp. 996-99. G.F. Bolling and R.H. Richman: Acta Metall., 1965A, vol. 13, pp. 745-57. J.W. Christian and S. Mahajan: Prog. Mater. Sci., 1995, vol. 39, pp. 1-157. H. Conrad: Progr. Mater. Sci., 1981, vol. 26, pp. 123-403. S. Mahajan and D.F. Williams: Int. Metall. Rev., 1973, vol. 18, pp. 43-61. C.J. Beevers and J.L. Robinson: J. Less-Common Met., 1969, vol. 17, pp. 345-52.
The Mechanism of Porous Column Formation during Spray Forming ZIN H. LEE, HAIMING HU, ENRIQUE J. LAVERNIA, and DAWN R. WHITE Spray-forming processes are currently being used to commercially fabricate billets, rolls, and pipes and are now under further development to produce plates and other near-net shapes.[1,2] Spray forming can also be applied for the rapid prototyping of dies, which requires spraying tool steel into a shaped mold.[3] In most of these applications, it is necessary to reduce porosity to a minimum value in the as-sprayed state, because further working of the die to achieve a full density is limited. Generally, three different types of porosity are known: dry porosity, wet porosity, and solidification shrinkage.[1,2,4,5] Dry porosity or interstitial porosity is formed when the deposit surface is too dry, i.e., has too low a liquid fraction and shows a large number of small pores at the unfilled interstices between droplets. Wet porosity or gas porosity is formed when the deposit surface is too wet, i.e., has too high a liquid fraction and shows a small number of large pores, which are typically entrapped gas that evolves during the impingement of droplets into the liquid layer at the surface. Solidification shrinkage is seldom observed but can develop if the surface cools faster after deposition, and the remaining liquid inside the deposit solidifies later. There is, however, an additional type of porosity that is occasionally observed during the deposition into shaped molds. Such porosity is present in the form of a column and exhibits very unique features, such as directionality. In the
ZIN H. LEE, Professor, is with the Department of Materials Science and Engineering, KAIST, Taejon, 305-701, Korea. HAIMING HU, Postdoctor, and ENRIQUE J. LAVERNIA, Professor, are with the Department of Biochemical and Chemical Engineering and Materials Science, University of California–Irvine, Irvine, CA 92697. DAWN R. WHITE, Principal Engineering Specialist, is with the Materials Systems Reliability Department, Ford Research Laboratory, Dearborn, MI 48121-2053. Manuscript submitted August 27, 1998. METALLURGICAL AND MATERIALS TRANSACTI
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