Physical Heterogeneities in Solidification

Structural and microstructural heterogeneities during solidification are described by analyzing dendrites and the resulting columnar structure for different cooling mechanisms in metallic ingots, including deformation of monocrystal structures. The effect of mold geometry on the formation of microcracks and stress concentration is explained, along with the effect of shrinkage and resulting defects of the final volume of solidified ingots justifying the use of risers. Techniques to improve quality of molded metallic parts with complex geometry are also mentioned and the evolution of gasses during solidification and its role in producing pores during dendrite or equiaxed crystals is exemplified with cross-section figures of steel slabs. The concepts of castability, soundness, and hot tearing are analyzed to evaluate best practices during casting of metallic parts as a function of fluidity and feeding rate of different alloys.