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

Constantin Böhm,Martin Werz,Stefan Weihe

doi:10.3390/met10091222

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.

Highlights

The laser powder bed fusion (LPBF) process, known as selective laser melting (SLM), can produce highly complex geometries at no extra manufacturing time
The results suggest that the dilution ratio is dependent on the penetration depth and the layer thickness
One way to surpass this limitation is welding of additive manufactured components to wrought components [1]. Another possibility is to build up on existing conventionally manufactured parts. This manufacturing method is a variant of hybrid manufacturing and could be applied in future applications to surpass the limitations of LPBF

Summary

Introduction

The laser powder bed fusion (LPBF) process, known as selective laser melting (SLM), can produce highly complex geometries at no extra manufacturing time. An additional benefit of LPBF is that the process parameters are adjustable in a wide parameter field. This allows reaching specific technological properties, namely, surface roughness or high density. One way to surpass this limitation is welding of additive manufactured components to wrought components [1]. Another possibility is to build up on existing conventionally manufactured parts.

Objectives

Results

Conclusion