On the Influence of AlSi10Mg Powder Recycling Behavior in the LPBF Process and Consequences for Mechanical Properties

Abstract

By using additive manufacturing techniques like the laser powder bed fusion (LPBF) process, parts can be manufactured with high material efficiency because unfused powder material can be reconditioned and reused in consecutive manufacturing jobs. Nevertheless, process by-products like spatters may influence the powder quality and hence alter the mechanical properties/performance of parts. In order to investigate these dependencies, a methodology and a standard build job for the recycling behavior of the lightweight aluminum alloy AlSi10Mg was developed and built with ageing powder in 10 consecutive jobs with no refreshing between the cycles. The powder properties and mechanical performance of parts at static load for two build directions (horizontally and vertically to substrate plate) was evaluated. The influence of build height effects on mechanical performance was investigated as well. The findings may indicate that the coarsening of the powder material during recycling could lead to improved mechanical properties for the AlSi10Mg alloy.

The effect of powder reuse on the surface chemical composition of the Scalmalloy powder in Powder Bed Fusion – Laser Beam process

“…In order to make the PBF‐LB/M process energy and economically sustainable, the recycling of powders becomes necessary. A strong relationship between powder recycling and the quality of the final part has been reported in the literature 22,23 . As extensively demonstrated by Wang et al, the effects of reuse are highly dependent on the type of alloy 24 .…”

“…A strong relationship between powder recycling and the quality of the final part has been reported in the literature. 22,23 As extensively demonstrated by Wang et al, the effects of reuse are highly dependent on the type of alloy. 24 In particular, aluminium is a strongly electronegative metal and its strong oxygen affinity explains the importance of monitoring the use of Al-based alloys in the PBF-LB/M process.…”

High-Temperature Mechanical Properties of Stress-Relieved AlSi10Mg Produced via Laser Powder Bed Fusion Additive Manufacturing

“…When setting up the experimental plan, it was assumed that the embedded oxides might help improve the high-temperature characteristics, as the respective performance of ceramic particle-reinforced Al-based metal matrix composites (MMCs) suggests. This notion is partially supported by Weiss et al, who showed that improvement in room temperature yield and ultimate tensile strength can indeed be observed in specimens based on recycled powders [ 24 ]. To verify this assumption, oxygen content was determined on printed samples using a trace element analyzer of type ONH2000 supplied by Eltra GmbH, Haan, Germany.…”

“…The study by Weiss et al also considered Al, Si, Mg and hydrogen content, showing significant variation in the case of oxygen only. Within this somewhat higher range of oxygen content, Weiss et al found no significant influence on density of LPBF samples and only a slight increase in Vickers hardness, with the latter exhibiting strong scatter [ 24 ].…”

“…The characteristics of this material have thus been studied previously and in detail by several authors. Among others, multiple studies are available which investigate the influence of factors such as scanning parameters [ 14 , 15 ], build orientation [ 14 , 16 , 17 , 18 ], post-processing including heat treatment [ 19 , 20 , 21 , 22 ] or state of powder, e.g., after recycling [ 23 , 24 , 25 ], on room temperature mechanical properties. Figure 1 provides an overview of the findings based on yield strength, ultimate tensile strength and elongation at failure and illustrates the effect of heat treatments on room temperature properties.…”