Interaction between primary dendrite arm spacing and velocity of fluid flow during solidification of Al-Si binary alloys

摘要

A new and more efficient numerical algorithm to simulate the solidification of binary metallic alloys, wherein for the first time, the undercooling of the liquidus temperature prior to solidification event and optimized thermo-physical properties was incorporated, has been recently developed and validated by various experiments. Subsequently, experiments were carried out to evaluate the validity of various theoretical models in the literature used to predict the dendrite arm spacing (DAS) and quantify the critical interaction between fluid flow and transient DAS during unsteady state solidification. Typically, models of solidification processes such as casting, welding and galvanizing assume a constant value of fluid flow to predict the DAS and in many cases unable to obtain validation. This practice is erroneous and the transient fluid flow developed during solidification has a significant effect on the transient DAS, thermal gradient (G), solidification velocity (R) and morphology of the mushy zone. The Bouchard-Kirkaldy model (DAS prediction) coupled with the Lehmann model to incorporate fluid flow velocity was the only valid theoretical model in binary alloy solidification.