Abstract
Mechanical properties and performance of metallic materials depend on their microstructures. In order to develop engineering materials that match prescribed criteria and to enable design with multifunctional materials, it is essential to be able to predict their microstructural patterns, such as size, shape, and spacing of the dendritic structures observed in solidified metals. In the cases of metallic alloys, which present dendritic structure, the mechanical properties of foundry products depend mainly on the primary- and secondary-arm. Therefore, it is important, in a computational simulation of the solidification processes, to use reliable methods to correlate the thermal parameters with secondary-dendrite arm spacing. This study presents a numerical model for prediction of secondary-arm spacing as a function of thermal parameters (cooling rates and local solidification time). Spacing of the arms for a binary alloy is numerically predicted using a phase-field model. Secondary dendrites calculated by phase-field model, they are similar to the ones found in experiments investigation of solidification in Al-Cu alloys. Arm spacing predicted in the present work, when compared with the experimental results, showed good agreement. Its estimation takes place at the late stage of growth. The effect of physical properties (partition coefficient (ke), diffusion in the liquid (DL) and diffusion in the solid phase (DS)) on secondary-arm spacing is systematically investigated by phase-field model. With the help of numerical results for Al-4.5wt%Cu alloy, the applicability of the phase-field model to the estimation of secondary-dendrite arm spacing during unidirectional solidification is demonstrated.
Highlights
Solidification is the main phenomenon taking place during casting
The results show that both the local solidification time and the secondary-arm spacing increased over the process
Two-dimensional simulations produced dendrite arms that are similar to the ones found in experiments reported in the literature
Summary
Solidification is the main phenomenon taking place during casting. This, in turn, has long been known as a relatively inexpensive means for producing metal goods. Phase-field models are known to be very powerful in describing non-equilibrium dendritic evolution They tend to be very efficient from the number-crunching standpoint on account of the fact all the governing equations are written for the whole domain, making no distinction between the interface and the solid and liquid phases. Phase-field models have, over recent years, garnered wide acceptance, given their ability to simulate the solidification process in the presence of a complicated solid/liquid interface. These models can be found in a collection of papers in the open literature. The secondary-arm spacing is evaluated with different values of partition coefficient and solute diffusivities in the liquid and solid regions
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