Microstructure simulation of maraging steel 1.2709 processed by powder bed fusion of metals using a laser beam: A cellular automata approach with varying process parameters

Abstract

Additive manufacturing via powder bed fusion of metals using a laser beam (PBF-LB/M) enables the fabrication of parts from metal powder with mechanical properties surpassing those of conventional processes. In this manufacturing process, a grain structure that is very sensitive to process parameter modifications and the resulting change in the temperature field is formed. Simulating the solidification microstructure is crucial for understanding process-microstructure relationships and creating digital twins for microstructure engineering and tailoring. This work introduces a cellular automata (CA) methodology for the microstructure simulation of maraging steel 1.2709 processed by PBF-LB/M. A high-resolution moving heat source model, based on the finite element method, was set up to capture the temperature field. The solidification microstructure was simulated by a two-dimensional CA model. Ten sets of process parameters have been used to produce single tracks experimentally to validate the CA model. The microstructure of these sets has been characterized by optical and scanning electron microscopy. The CA model successfully captures the essential solidification characteristics. The grain sizes have demonstrated a significant sensitivity to initial conditions. In-depth analysis has revealed that process parameters and thermal conditions, rather than the energy density, critically influence the grain size and the aspect ratio. Meanwhile, the grain alignment angle has shown no explicit dependency on process parameters, underscoring the complex dynamics governing microstructural evolution. This methodology paves the way for advancing material design in various industries by enabling a precise control over mechanical properties through microstructure tailoring.