Influence of laser scan speed on micro-segregation in selective laser melting of an iron-carbon alloy: A multi-scale simulation study

Abstract

Selective laser melting (SLM) is an additive manufacturing method complementary to traditional manufacturing technologies, and it has drawn increasing amount of attention in recent years. However, effective control of microstructure evolution in SLM is usually difficult due to the rapid heating and cooling cycles involved in the process. In this research, multiscale simulation is performed to investigate the influence of laser scan speed on micro-segregation in SLM of binary Fe-C alloy, with the consideration of realistic thermal history and powder-to-dense phase transformation. Meso-scale finite element method (FEM) is used to calculate the temperature field, and micro-scale phase field (PF) method is used to calculate the dendrite evolution and solute redistribution. Three levels of laser scan speeds, i.e., 1000, 1600, and 2400 mm/s are used to perform the simulation. The results indicate that the overall melt pool morphology and temperature distribution are significantly affected by the laser scan speed. Higher scan speed leads to significantly higher cooling rate in the interested solidification region, and therefore alters the dendrite growth velocity and tip radius. Moreover, higher laser scan speed results in lower interdendritic segregation ratio, due to ultra-fast cooling and solute trapping.