CONtrol - Contamination-tolerant hypoeutectic and hypereutectic Al-Si alloys for additive manufacturing

Although the lasers used in production are becoming increasingly powerful and brilliant, the materials available are often completely unsuitable for the processing tasks required today. To date, metal powders developed more than 50 years ago for a completely different process - thermal spraying - have been used in additive manufacturing. In modern laser-based additive processes, however, these powders lead to process instabilities as well as porosities and defects in the component. There is therefore an urgent need to adapt the materials to these widely used manufacturing processes, as laser-based processes will dominate as important production processes in the long term due to their throughput and precision. This requires a fundamental research approach that starts at the very beginning of the process chain,the material.

A coordinated, coherent research programme that brings together materials development and photonics research for the first time and starts at the material synthesis stage should help to tap this considerable potential. In order to ensure feedback between process behaviour and material properties, SPP 2122 funds tandem projects from the fields of "materials" and "laser processes" that collaborate across projects in various thematic clusters.

Leibniz-IWT is addressing this topic with the project "CONtrol - Contamination-tolerant hypoeutectic and hypereutectic Al-Si alloys for additive manufacturing" together with the University of Bremen. In it, the influence of Fe contamination on Al-Si alloys is being investigated so that the contamination can be compensated for by adapted process conditions.

The recycling of aluminium brings with it various impurities, such as iron. It is known that iron forms intermetallic phases in aluminium alloys, which can lead to brittleness of the overall material if they are too large. Synthesis with high cooling rates, as used in additive manufacturing, can offer an interesting recycling route. In this way, additive manufacturing could become a central process in sustainable, closed-loop material chains. This project therefore investigates the influence of Fe contamination on two Al-Si alloys with silicon concentrations of 10 wt% (hypoeutectic) and 20 wt% (hypereutectic). While AlSi10 is a common alloy for LPBF, the process window for processing becomes smaller with increasing silicon content. By systematically varying the Fe contamination, its influence on the thermophysical properties, melt pool conditions, phase formation and defect structure of the fabricated components can be understood. Based on the characterisation of the additively manufactured samples, models are developed to describe the melt pool characteristics, the microstructure, the defect formation and the mechanical properties.

Further information on the priority programme.