University of Manchester study advances ValCUN’s Molten Metal Deposition

Scientists at The University of Manchester, England, UK, have demonstrated how careful control of processing temperatures in Molten Metal Deposition (MMD) technology from ValCUN, Ghent, Belgium, can significantly reduce defects and refine the microstructure of aluminium components, providing further evidence of the process’s potential for industrial metal Additive Manufacturing.

Published in Materials & Design, the study investigated aluminium alloy 4043 produced using MMD, a metal Additive Manufacturing process developed by Belgium-based ValCUN. Unlike many established metal AM technologies, as the name suggests, MMD deposits already-molten metal, enabling processing at lower and more controllable temperatures than laser-based machines while potentially reducing energy consumption and thermal stresses.

The researchers examined how varying nozzle and substrate temperatures influenced grain structure, crystallographic orientation and porosity in printed components. They found that relatively small changes in processing parameters had a significant impact on the resulting microstructure and defect content.

The researchers examined how varying nozzle and substrate temperatures influenced grain structure, crystallographic orientation and porosity in printed components. They found that relatively small changes in processing parameters had a significant impact on the resulting microstructure and defect content.

“Understanding how processing conditions affect the internal structure of a printed component is essential if Additive Manufacturing technologies are to be used more widely in demanding industrial applications. Our study shows that relatively small adjustments in manufacturing temperatures can have a major impact on defect formation and microstructural development,” stated Dr Fan Wu and Dr Wajira Mirihanage, co-authors from the Department of Materials, The University of Manchester.

While metal Additive Manufacturing offers the ability to produce complex geometries with reduced material waste, many established processes involve rapid heating and cooling cycles that can introduce porosity, residual stresses and distortion. By depositing molten aluminium directly, MMD reduces the severity of these thermal cycles, offering an alternative route to producing aluminium components.

To investigate the process, the team manufactured aluminium alloy 4043 specimens using different nozzle and substrate temperature combinations before analysing grain morphology, crystallographic texture and porosity using advanced microscopy. Mechanical testing was also performed to evaluate hardness and elastic modulus.

The study found that higher nozzle and substrate temperatures slowed cooling during deposition, promoting grain growth and increasing porosity. Lower substrate temperatures accelerated cooling, producing finer equiaxed grain structures and reducing defect levels. Reducing the substrate temperature from 530°C to 480°C decreased the average grain size from approximately 126 µm to 54.19 µm.

The researchers also observed that porosity generally decreased in larger specimens, where longer deposition times allowed gases to escape more effectively during manufacture. In addition, defect levels and grain size tended to decrease as successive layers were deposited, indicating that changing thermal conditions throughout the build influence material solidification.

At the highest process settings investigated – a substrate temperature of 530°C and nozzle temperature of 880°C – the material developed a preferential <100> crystallographic orientation alongside a greater proportion of columnar grains, reflecting reduced nucleation during solidification.

Despite the presence of some porosity, the additively manufactured components exhibited mechanical properties comparable with conventionally manufactured aluminium alloy 4043. Hardness values ranged from 46.5–47.6 HV, while elastic modulus values ranged from 92.8–110.3 GPa, demonstrating the process’s potential for engineering applications.

Dr Wu and Dr Mirihanage added, “Molten Metal Deposition is still a relatively new manufacturing technology, and there is currently limited understanding of how processing conditions affect the final material. By establishing clear links between processing parameters, microstructure and defect formation, this work provides a foundation for optimising future manufacturing strategies and improving the reliability of aluminium components produced using MMD.”

The authors conclude that the strong relationship between controllable process parameters and porosity demonstrates considerable scope for systematic defect control in MMD. They believe the findings will support further optimisation of the technology for industrial applications requiring high-quality, consistent aluminium components.

‘Microstructural evolution and defect formation in aluminium alloy 4043 during molten metal deposition’ is available here.

www.manchester.ac.uk

www.valcun.be