Dilution Ratio and the Resulting Composition Profile in Dissimilar Laser Powder Bed Fusion of AlSi10Mg and Al99.8

Abstract

A variant of a hybrid manufacturing process combines the benefits of laser powder bed fusion (LPBF) and conventional manufacturing. Hybrid manufacturing can result in dissimilar material combinations which are prone to process errors. This study is motivated by the future application of a hybrid manufacturing variant and focusses on dissimilar aluminium alloys were hot cracks are the dominant process errors. A theoretical model was derived for the composition profile based on the dilution ratio known from fusion welding. The theory was validated with penetration depth measurements and energy-dispersive X-ray spectroscopy line scans on samples manufactured by LPBF (powder AlSi10Mg, building platform Al99.8 and line energies Pv−1 = 0.26–0.42 J·mm−1). A material combination with a low hot crack susceptibility was chosen to establish the theory. The results suggest that the dilution ratio is dependent on the penetration depth and the layer thickness. The used line energies result in a dilution ratio of 67–86% which results in 2–6 re-melted and mixed layers per added layer. A specific process design metric, the mixture height, is proposed to estimate the spatial effect of the dilution. The results can be used to adjust process parameters to lessen the effect of process errors in dissimilar hybrid manufacturing and increase mechanical performance.

Emerging metallic systems for additive manufacturing: In-situ alloying and multi-metal processing in laser powder bed fusion

“…The intermetallic compounds formed in the interface also led to anomalous readings for microhardness due to the precipitation of such compounds that are harder but more brittle (Figure 29). Böhm et al derived a theoretical model for the composition profile for multi-metal processing by L-PBF using AlSi10Mg and pure aluminum [156]. The model takes into account the dilution ratio as a function of the penetration depth of the melt pool, which is in turn dependent on the process parameters.…”