International Congress on Engineering, Sciences and Innovative Technologies (ICESIT 2020) - Kuala Lumpur - Malaysia (2020-02-13)

Numerical Simulation of Grain Structure and Macrosegregation during DC Casting
Numerical Simulation of Grain Structure and Macrosegregation during DC Casting Houfa Shen*, Qipeng Chen School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China, shen@tsinghua.edu.cn Keywords: solidification, direct chill casting, grain structure, macrosegregation, numerical simulation Modeling of the macrosegregation and grain structure during direct chill (DC) casting of Al-6.0wt%Cu round billets is carried out with a transient model, by which the macroscopic transport of mass, momentum, energy and solute is coupled with the nucleation, grain growth and dendrite tip growth kinetics. The billet is described by a two-dimensional (2D) axisymmetric model, and a Lagrangian representation is used for coupling macroscopic transport and grain structure calculations by extending the calculation domain from the top surface. Fully coupled and transient simulations are performed, and the grain structure and macrosegregation induced by thermal and solutal convection are studied. The results show that grains tend to be finer and grow in a direction more perpendicular to the axis, and the positive segregation near the centreline becomes more pronounced with the increasing casting speed. The increasing casting temperature makes grains coarser and the negative segregation near the surface more pronounced. The grain structure is fully equiaxed in the grain-refined billet, while a fine columnar grain region and a coarse columnar grain region are formed in the middle part and bottom part of the non-grain-refined billet, respectively.
Dr. Houfa Shen