Formation of Microstructures, Grain Textures, and Defects during Solidification
Résumé
In most manufacturing processes, the structures formed during solidification influence to a large extent the final mechanical properties of the product. (In this article, macrostructure refers to the structure of primary dendritic grains only, or the structure of eutectic grains in eutectic alloys, while microstructure refers to the internal structure of these grains, such as dendritic, peritectic, and eutectic patterns. The term structures covers both the micro- and macrostructures. The terms micro- and macroscopic are also used to refer to the corresponding length scales.) The influence of the solidification structures is not only important for casting processes but also for wrought alloy materials, because the behavior during subsequent processes, such as homogenization, aging, rolling, extrusion, and so on, is largely dependent on the as-cast state. Strict specifications of the as-cast state are therefore generally imposed regarding the grain size, type, volume fraction, and morphology of the various microstructure constituents. As part of the process of controlling and optimizing the as-cast structures, numerical simulation is becoming increasingly important.