Numerical modelling of in-situ alloying of Al and Cu using the laser powder bed fusion process: A study on the effect of energy density and remelting on deposited track homogeneity

• Published in: Additive manufacturing Vol. 59; p. 103179
• Main Authors: Chouhan, Arvind, Hesselmann, Marcel, Toenjes, Anastasiya, Mädler, Lutz, Ellendt, Nils
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2022
• Subjects: Alloy homogeneity; In situ alloying; LPBF; Ray tracing; Remelting; Simulation; Ray tracing; In situ alloying; Alloy homogeneity; LPBF; Simulation; Remelting
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2022.103179

In-situ alloying using laser powder bed fusion (LPBF) allows for formation of new alloys and complicated components with spatially controlled characteristics. A major issue in in-situ alloying is the macro-segregation of alloying elements, that results in chemical inhomogeneity. The precise control of composition is one of the most important steps in any effective in-situ alloying process. In this study, a mesoscale computational fluid dynamics (CFD) model for simulating single-tracks is developed to advance the in-depth understanding of in-situ alloying of dissimilar metals. Surface tension and recoil pressure driven flows at the free surface, rapid phase change, laser reflections, and other physical phenomena affecting the LPBF process have all been examined. Species conservation is used to trace the mixing of different metals. Simulations are performed by melting a layer of Al powder on a Cu substrate, and the impact of recoil pressure and Marangoni convection driven flows on Al-Cu mixing was addressed. The homogeneity of the simulated track is quantified by defining a mixing index. The effect of different laser energy densities and remelting on the homogeneity of the deposited track is investigated. Numerically, it was observed that the high thermal conductivity of both metals results in a sharp and short melt pool, and rapid solidification of such a melt pool generates a heterogeneous concentration dispersion. At high energy density, a low mixing index value is observed, indicating improved homogeneity in the deposited track. Furthermore, remelted tracks have a low mixing index value, indicating that remelting is an effective strategy for improving homogeneity. This study provides fundamental insights on the mixing of dissimilar metals and aims to support future research activities on the design and development of new alloys using LPBF process.