Micro-scale thermodynamic model of microstructure and stress evolution in parts via selective laser melting

The thermodynamic state changes during selective laser melting (SLM) processing dominate the microstructure and mechanical properties of the built parts. Improper operational parameters often lead to uneven microscopic morphology, microcracks, distortions, and other failures. The key to controlling the microstructure of the forming metal lies in an in-depth understanding of the micro-scale thermodynamics of this process. A micro-scale thermodynamic model was developed herein to predict the microstructure and internal stress evolution in parts fabricated by SLM with two typical scanning strategies. The modified two-temperature (TTM) model was employed to discover the dominant interface thermodynamic phenomenon in unitary path scanning and the novel symmetrical multi-path scanning capable of reliving residual stress and homogenizing microstructure. The real-time identifying method of temperature, microstructure, and stress could be further applied to closed-loop control of the SLM process.