07/12/2010

Solidification: a modern approach to the field

cu_ag_solidification.gifSolidification processes are familiar to all of us, whether they concern the formation of frost on windows or ice in trays, the freezing of solders in electronic circuits, or the casting of aluminum and steel in industrial practice. Solidification has long represented a major force in human development, and some of the “Ages” of man have even been classified by the alloys that the inhabitants were able to melt and cast. During the Bronze Age, ca. 4000 BC - 1200 BC, copper-based weapons and other artifacts of daily life were common throughout Europe and Asia. However, once it became possible to melt and alloy iron, ca. 1200 BC, this metal quickly replaced bronze for weapons and other applications because of its superior properties. Several variants of steel, the most famous of which is the legendary Damascus steel, were produced in ntiquity by mechanical means.


The invention of the Bessemer process in 1858 led to the mass production of steel in liquid form, which was then cast into shapes and ingots for wrought processing. This was one of the key inventions of the industrial revolution, and provided the foundation for  transportation by rail, and later by automobile. Similarly, the Hall-H´eroult process for producing aluminum, invented in 1886, enabled the mass production of aluminum cast products, which in turn gave rise the aircraft industry in the following century.

The ability to produce these metals in liquid form made it possible to easily manufacture alloys of controlled composition, which could then be cast into either final products or into ingots that, in turn, would be deformed in the solid state into plates, sheets, billets, and other wrought products. The solidification process marked the stage of production where the composition and structure were set for all future processing. Through the first half of the 20th century, metallurgists developed an understanding of how the properties of cast products were related to the conditions extant during the solidification process.

One could argue that the art and practice of solidification entered the realms of engineering and science with the publication of Chalmers’landmark text Principles of Solidification in 1964, which presented some of the basic models for solute partitioning during the freezing of alloys, and helped to explain how microstructural patterns such as dendrites evolve during planar or spherical growth. Ten years later, Flemings’ Solidification Processing extended this modeling approach to develop models for the evolution of measurable microstructural features, such as dendrite arm spacing and segregation patterns. These models began to quantify the effect of processing parameters such as the cooling rate and the temperature gradient, as well as their interaction with alloy properties such as the freezing range and the underlying phase diagram on the final structure. Over the next decade, many important advances were made in the understanding of pattern formation in solidification microstructures, in particular regarding length scales in dendritic growth. Largely as a result of these advances, Kurz and Fisher published Fundamentals of Solidification, which focused in greater detail on the evolution of microstructure.

The book is intended to be the next entry in this line. The time since the publication of Kurz and Fisher’s text has seen the advent of large scale computation as a tool for studying solidification. This has allowed significant advances to be made in both theory and application. The development of phase-field methods has permitted a further understanding of the evolution of complex microstructures, and the availability of inexpensive large-scale computers and commercial software packages now allows process engineers to perform realistic simulations of macroscopic heat transfer, solute transport and fluid flow in realistic geometries. The development of volume averaging methods and the statistical representation of microstructures provide a bridge between the microscopic and macroscopic scales.

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Les auteurs :

Jonathan Dantzig, Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign.

Michel Rappaz, ingénieur diplômé de l'Ecole polytechnique fédérale de Lausanne en 1973, obtient le titre de docteur ès sciences du Département de physique de la même école en 1978.

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