PurposeThe motivation for this work is to establish a model that not only includes the main factors resulting in macrosegregation but also retains simplicity and consistency for the sake of potential application in casting practice.Design/methodology/approachA mathematical model for the numerical simulation of thermosolutal convection and macrosegregation in the solidification of multicomponent alloys is developed, in which the coupled macroscopic mass, momentum, energy and species conservation equations are solved. The conservation equations are discretized by using the control volume‐based finite difference method, in which an up‐wind scheme is adopted to deal with the convection term. The alternative direction implicit procedure and a line‐by‐line solver, based on the tri‐diagonal matrix algorithm, are employed to iteratively solve the algebraic equations. The velocity‐pressure coupling is handled by using the SIMPLE algorithm.FindingsBased on the present study, the liquid flow near the dendritic front is believed to play an important role in large‐scale transport of the solute species. The numerical or experimental results in the literatures on the formation of channel segregation, especially those about the location of the initial flow as well as the morphology of the liquidus front, are well supported by the present investigation.Research limitations/implicationsThe modelling is limited to dealing with the thermosolutal convection of two‐dimensional cases. More complicated phenomena (e.g. crystal movement) and 3D geometry should be considered in future research.Practical implicationsThe present model can be used to analyze the effects of process parameters on macrosegregation and, with further development, could be applied as a useful tool in casting practice.Originality/valueThe numerical simulation demonstrates the capability of the model to simulate the thermosolutal convection and macrosegregation in alloy solidification. It also shows that the present model has good application potential in the prediction and control of channel segregation.

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In order to study the development of thermal stress and to predict the hot tearing and residual stress of shaped casting, two models were used to carry out the stress analysis of the two stages of solidi®cation. The rheological model [H]±[HuN]±[NuS] was used for the quasi-solid zone while the thermo-elasto-plastic model was used for the period after solidi®cation. Coupling the thermal analysis based on the ®nite different method with the stress analysis based on the ®nite element method, a FDM/FEM integrated system of thermal stresses analysis during the solidi®cation process was developed. After experimental veri®cation, the system was put into practical application. The analysis results during the quasi-solid zone show that the visco-plastic strain is an important factor for the occurrence of hot tearing. The hot tearing of a case steel casting and the residual stresses and deformation of a hydro-turbine blade steel casting were analyzed and predicted using the system. The simulation and the practical results were basically in agreement.

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