Adrian V. Catalina

Melt convection effects on the critical velocity of particle engulfment

Liquid convection ahead of the solidifying interface alters particle behavior in the vicinity of the interface. This effect has not been quantified to date. Relevant directional solidification experiments were conducted using samples of varying thicknesses, as well as normal and low-gravity experiments. A mixture of transparent biphenyl matrix and spherical glass particles, as well as one of succinonitrile matrix with polystyrene particles were used. Two experimental setups were used: a horizontal gradient heating facility (HGF) for horizontal solidification, and a Bridgman-type furnace (BF) for vertical solidification. The convection level during solidification in the HGF was varied by changing the distance between the glass slides containing the composite sample. The BF was used on ground and during parabolic flights, and thus the convection level was changed by alternating low-gravity and high-gravity solidified regions. It was found that the convection level and/or particle buoyancy significantly influences the critical velocity for particle engulfment. At higher natural convection during solidification the critical velocity increases by up to 40%. At very high convection levels engulfment may become impossible because particles fail to interact with the interface. A systematic analysis of some theoretical models was performed in an attempt to evaluate the present level of theoretical understanding of the problem. Methods of evaluating the surface energies required for model validation are also presented.

Lamellar Growth of Eutectic Equiaxed Grains

ADRIAN V. CATALINA and DORU M. STEFANESCUAlthough a large amount of work was done in the fieldof eutectic solidification, it was conducted mostly for di-rectional solidification. Little attention was paid to equiaxedgrowth. Recent developments in macrotransport-transfor-mation kinetics modeling, however, require models forgrowth of equiaxed eutectic grains during continuous cool-ing. The purpose of this article is to extend the generaltheory of Jackson and Hunt to eutectic systems solidifyingwith equiaxed grains.The Jackson–Hunt (JH) theory

Advances in the science and engineering of casting solidification : An MPMD symposium honoring Doru Michael Stefanescu

Advances in the science and engineering of casting solidification : An MPMD symposium honoring Doru Michael Stefanescu

Advances in the Science and Engineering of Casting Solidification

Many of the metal casting processes are still empirical in nature. Many others are deeply rooted in mathematics and therefore, suitable for modeling. Science of casting and solidification is a major technical asset for foundry operations and of extreme importance in understanding different length scales microstructural changes and evolution as well as developing new processes and materials. In his attempt to describe combinations of solidification theory, research results and industrial practice, Professor Doru Michael Stefanescu (ASM Fellow, 1997) has made tremendous contributions to the field. Many of his views on casting and solidification are valued as important impacts within professional environments such as TMS and ASM International. He has written many articles for the ASM Handbook series on subjects including basic metallurgy of cast iron, compacted graphite irons, solidification, thermodynamic properties of iron-base alloys, and computational modeling. He was also Volume Chair for Volume 15: Casting, of the 9 Edition Metals Handbook.