Semisolid metal (SSM) processingis a relatively new technology for metal forming. Different from the conventional metal forming technologies which use either solid metals (solid state processing) or liquid metals (casting) as starting materials, SSM processing deals with semisolid slurries, in which non-dendritic solid particles are dispersed in a liquid matrix. Semisolid metal slurries exhibit distinctive rheological characteristics: the steady state behaviour is pseudoplastic (or shear thinning), while the transient state behaviour is thixotropic. All the currently available technologies for SSM processing have been developed based on those unique rheological properties, which in turn originate from their non-dendritic microstructures. Year 2001 marks the 30th anniversary of the concept of SSM processing. Today, SSM processing has established itself as a scientifically sound and commercially viable technology for production of metallic components with high integrity, improved mechanical properti...

Semisolid metal processing

Buoyancy driven convection in a rectangular enclosure with a transverse magnetic field

We present a bibliography on moving and free boundary problems for the heatdiffusion equation, particularly regarding the Stefan and related problems. It contains 5869 titles referring to 588 scientific Journals, 122 books, 88 symposia (having at least 3 contributions on the subject), 30 collections, 59 thesis and 247 technical reports. It tries to give a comprehensive account of the western existing mathematicalphysical-engineering literature on this research field. RESUMEN Se presenta una bibliografía sobre problemas de frontera móvil y libre para la ecuación del calor-difusión, en particular sobre el problema de Stefan y problemas relacionados. Contiene 5869 títulos distribuidos en 588 revistas científicas, 122 libros, 88 simposios (teniendo al menos 3 contribuciones en el tema), 30 colecciones, 59 tesis y 247 informes técnicos o prepublicaciones. Se da un informe amplio de la bibliografía matemática, física y de las ingenierías existente en occidente sobre este tema de investigación. Primary Mathematics Subject Classification Number (*): 35R35, 80A22 Secondary Mathematics Subject Classification Number (*): 35B40, 35C05, 35C15, 35Kxx, 35R30, 46N20, 49J20, 65Mxx, 65Nxx, 76R50, 76S05, 76T05, 93C20. (*) Following the 1991 Mathematics Subject Classification compiled by Mathematical Reviews and Zentralblatt fur Mathematik. Primary key words: Enthalpy formulation or method, Filtration, Free boundary problems, Freezing, Melting, Moving boundary problems, Mushy region, Phase-change problem, Solidification, Stefan problem. Secondary key words: Continuous mechanics, Diffusion process, Functional analysis, Heat conduction, Mathematical methods, Numerical methods, Partial differential equations, Variational inequalities, Weak solutions. Palabras claves primarias: Método o formulación en entalpía, Filtración, Problemas de frontera libre, Congelación, Derretimiento, Problemas de frontera móvil, Región pastosa, Problema de cambio de fase, Solidificación, Problema de Stefan. Palabras claves secundarias: Mecánica del continuo, Procesos difusivos, Análisis funcional, Conducción del calor, Métodos matemáticos, Métodos numéricos, Ecuaciones diferenciales a derivadas parciales, Inecuaciones variacionales, Soluciones débiles. El manuscrito fue recibido y aceptado en octubre de 1999. D.A. Tarzia, A bibliography on FBP. The Stefan problem, MAT Serie A, # 2 (2000). 3

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A bibliography on moving-free boundary problems for the heat-diffusion equation. The stefan and related problems

In the first part of this paper, the working principle of a new electromagnetic continuous casting process is described. The main peculiarities of this process are (1) the presence in the sump of a strong electromagnetically driven forced convection, which promotes the production of a fine equiaxed structure, and (2) the fact that the thickness of the segregation zone tends toward zero. Local measurement methods are applied to the study of electromagnetic and hydrodynamic phe-nomena inside the sump of aluminum alloy billets. Further, the evolution of both the grain size and the thickness of the segregated surface layer with the electric power input is presented. In summary, this new technology presents the advantages of avoiding the addition of grain refiners and substantially reducing the scalping operation.

Electromagnetic refining of aluminum alloys by the CREM process: Part I. Working principle and metallurgical results

It is well known that ultrasonic melt treatment (UST) promotes grain refinement in aluminum alloys. Cavitation-aided grain refinement has been studied for many years; however, it is still not being applied commercially. The current article summarizes the results of experimental work performed on various alloying systems at different stages of solidification. The influence of UST parameters and solidification conditions on the final grain structure is analyzed. It was found that small additions of zirconium and titanium can significantly increase the efficiency of UST, under the stipulation that grain refinement is performed in the temperature range of primary solidification of Al3Zr. The possible mechanisms for this effect are discussed.

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Criteria of Grain Refinement Induced by Ultrasonic Melt Treatment of Aluminum Alloys Containing Zr and Ti

Local velocity and mass transfer measurements in molten metals using an incorporated magnet probe

A new magnetohydrodynamic method of transmitting forced vibrations to solidifying aluminum alloy melts has been developed. Contrary to the case of the conventional mechanoacoustic systems, this device lends itself very well to a fundamental investigation. The relatively accurate knowledge of both the electromagnetic pressure and the local velocity peaks has enabled us to reveal the specific effects of the oscillatory flow and of the cavitation phenomena on grain refinement. It has been shown that the cavitation threshold depends both on the surface state of the crucible internal walls and on the electromagnetic pressure peak. In the presence of well-developed cavitation situations, a very fine and homogeneous microstructure has been observed throughout the ingot. A laboratory prototype of a new magnetohydrodynamic cavity resonator, allowing for significant energy saving and likely to be used for industrial applications, including the elaboration of metal matrix composites by means of a preform infiltration process, was also the subject of experimentation.

Effects of forced electromagnetic vibrations during the solidification of aluminum alloys: Part I. solidification in the presence of crossed alternating electric fields and stationary magnetic fields

An experimental investigation, described in Part I and bearing on aluminum alloy billets produced by the CREM process, has shown that the main characteristics of this new technology are the elimination of the need for grain-refiner master alloys and a marked reduction of the scalping operation. Part II reports on the examination of the problems specific to the CREM process, which occur particularly during slab casting. The three-dimensional (3-D) aspect of the electromagnetic and fluid flow phenomena, the effect of the electrical conductivity of the ingot mold, and the improvement of the process design are examined.

Electromagnetic refining of aluminum alloys by the CREM process: Part II. Specific practical problems and their solutions

The influence on grain refinement of electromagnetic vibrations imposed during solidification of various aluminum alloys has been examined. The vibrations were produced, without any material contact with the solidifying alloys, by the simultaneous application of a stationary magnetic fieldB
 0 and a periodic magnetic fieldb(t) of 50 Hz frequency. Extensive grain refinement has been observed in both continuous casting and batch-type mold casting. This investigation shows that the mean grain size obtained by this electromagnetic vibrational method is smaller than that produced by the variable magnetic field acting alone (electromagnetic stirring), particularly when the alloys are characterized by a narrow freezing range.

Effects of forced electromagnetic vibrations during the solidification of aluminum alloys : Part II. Solidification in the presence of colinear variable and stationary magnetic fields

Charles Vives

Papers

Electromagnetic refining of aluminum alloys by the CREM process: Part I. Working principle and metallurgical results

Local velocity and mass transfer measurements in molten metals using an incorporated magnet probe

Effects of forced electromagnetic vibrations during the solidification of aluminum alloys: Part I. solidification in the presence of crossed alternating electric fields and stationary magnetic fields

Electromagnetic refining of aluminum alloys by the CREM process: Part II. Specific practical problems and their solutions

Effects of forced electromagnetic vibrations during the solidification of aluminum alloys : Part II. Solidification in the presence of colinear variable and stationary magnetic fields