Milestone Achieved in WP3: First Batch of Aluminum Powder Produced and Characterized

GEAR-UP has reached an important milestone in work package 3 (WP3): the team at Eurecat has successfully produced the first batch of aluminum alloy AlSi10Mg. This batch provides the baseline for understanding how high-quality materials can be made from recycled sources.

WP3 focuses on both producing and testing aluminum alloy powder that contain higher levels of trace elements – the small amounts of additional elements that naturally appear in recycled metals. Studying how these trace elements influence the performance of the final product is essential toward understanding how recycled materials can be reliably incorporated into manufacturing processes.

The team has now produced and characterized an entire batch of standard composition AlSi10Mg, pictured below in order of increasing magnification. The images were taken with a microscope known as a scanning electron microscope (SEM), using two different imaging settings:

1. Backscattered scanning electron (BSE) imaging: High-energy electrons are shot at the sample of interest. Based on the amount of electrons reflected back from the sample, the detector can give an indication of the atomic weight of the material. This creates the high-contrast diagrams that we see, where the compositional contrast is based on the atomic weight of the material. Heavier elements backscatter more efficiently, appearing brighter, making BSE ideal for distinguishing material phases.
2. Secondary electron (SE) imaging: Unlike BSE, a beam of low-energy electrons is shot at the sample. Due to their low energy, only the secondary electrons in the top few nanometers of the sample surface can escape.  These electrons are attracted to the positively-charged detector, creating a high-resolution image based on the surface topography.

The composition of the next two batches to be produced have been chosen based on the consortium’s experience with how trace elements can affect both the manufacturing process and the quality of the final product. Eurecat determined the final formulation after carrying out various experimental trials where they deliberately created variations in the main alloying and trace elements. This allowed them to study various properties – such as wettability and surface tension – where marked differences in melt fluidity were finally used to determine the final formulation.

After choosing and creating the alloy composition, the raw materials are first cleaned, pre-melted, and processed into ingots. With the materials thus prepared, they are converted into powder form using a process known as centrifugal atomization. In this method, the material is melted and poured onto a rapidly spinning disk or cup. The high rotational speed flings the liquid metal outward, breaking it into tiny droplets. As these metal droplets fly through the air, they cool and solidify into the fine, spherical powder particles. The process is common in manufacturing processes that require high-quality, flowable metal powders with narrow particle size distribution.

As part of the characterization of the first powder batches, the team must examine particle size distribution and morphology. The team compares the chemical composition of the powder with the raw material to identify any deviations during the atomization process. They pay special attention to the microstructure of the resulting powders, as trace elements can play a significant role in how the material behaves.

The next step is to use these powders to manufacture test coupons for mechanical characterization with laser-based powder bed fusion (PBF-LB). The results will contribute toward the ongoing mission to determine how recycled aluminum can be best integrated in advanced manufacturing applications.