In situ TEM helps to understand the microstructural changes in AlSi10Mg during 3D printing and post processing

 
Original article by Mihaela Albu, Robert Krisper, Judith Lammer, Gerald Kothleitner, Jacopo Fiocchi and
Paola Bassani
Dental crown created by selective laser melting (SLM)

Dental crown created by selective laser melting (SLM)

Selective laser melting (SLM) is an additive manufacturing technique used to create unique products for the medical technique, automotive-, aeronautic- and space industry. AlSi10Mg alloy is widely used for this technique because of its low weight, corrosion resistance, good thermal properties, specific strength, and flexible post processing capabilities. The mechanical properties of 3D printed parts show better values compared to parts that are made using traditional casting of metal. But these values decrease after conventional heat treatment. In this research, scientists from Graz Centre for Electron Microscopy, Austria, tried to understand the fundamental mechanisms responsible for the drop in mechanical properties after heat treatment.

This work provides the first correlative in-situ heating multiscale analysis of the powder and the additive produced AlSi10Mg alloy, allowing a unique insight into material transitions at the micro-and nanoscale. The researchers showed that microstructural changes like crystallization of eventually present amorphous phases and the evolution of Si nanoparticles evenly dispersed in the Al-matrix are the most important factors that contribute to the enhancement or decrease of the mechanical properties.

Towards affordable 3D metal printing

Nowadays, selective laser melting (SLM) refers to the most common system used to create metal parts from powders as feedstock. Despite its popularity, powder based additive manufacturing is still an expensive process, and consequently, getting proof components at the first attempt is of great economic interest. Manufacturers of such parts strive for optimizing their processes, not only to improve material properties, but also to enhance the interchangeability of building platforms and thus, their economic flexibility. Controlling these production aspects and finding an adequate post-processing strategy helps to fine-tune the microstructural features, and therefore the mechanical properties, according to different application fields.

Low magnification HAADF STEM video 80°C to 360°C in 20°C steps for the as-built sample, maintaining the isothermal stages for 4 min each
Atomic resolution video of a Si nanoparticle in the Al-matrix during in-situ heating

Benefits of in situ STEM

In-situ heating experiments in scanning transmission electron microscopes (STEM) enable immediate information about the structural, morphological and chemical changes and are thus helpful for the selection of various post-processing strategies.

DENSsolutions Wildfire System TF FEI

The DENSsolutions Wildfire H +DT system enabled the fast heating and cooling that allowed us to perform nanoscale crystallographic and chemical analyses at certain temperatures that corresponded to the exothermic peaks in DSC measurements and to the in-situ XRD measurements.

Dr. Mihaela Albu
“In-situ heating experiments performed on 3D printed materials enable breakthrough advances in printing and post-process optimization. DENSsolutions Wildfire system proved to have superior thermal and spatial stability, ensuring high-resolution investigations at higher temperatures.”

Dr. Mihaela Albu
Senior Scientist | TEM at the Austrian Centre for Electron Microscopy and Nanoanalysis

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