5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Additive manufacturing by Laser Powder-Bed Fusion (LPBF) is accompanied by solidification under large thermal gradients and cooling rates. As a consequence, solidification morphologies between dendritic with only limited sidebranches or rather cellular pattern are commonly observed. The growth regime is characterized by Péclet numbers of order or larger than 1 (with cell tip radii of order or larger than the length scale of the diffusive pile-up in the melt), and by significant kinetic effects at the solid/liquid interface. We will present results from 2D and 3D phase-field simulations of primary solidification of the Ni based alloy IN718 for a range of solidification rates (1 ... 10 cm/s) and temperature gradients (10^5 K/cm ... 10^6 K/cm) typically seen in LPBF. The operating state of the growth front will be discussed in terms of cell tip shapes, growth undercooling, primary spacing and the effect of crystallographic orientation. A general observation is that, for such high Péclet numbers, usual mechanisms of spacing selection and accommodation are less effective. Cellular morphologies and spacing variations show good agreement with experimental data for IN718.