Scientists at The University of Manchester have uncovered how subtle changes in temperature during a promising metal 3D-printing process can significantly affect the quality of aluminium components.
The study published in Materials & Design investigated molten metal deposition (MMD), an additive manufacturing technology. Unlike many established metal 3D-printing techniques, MMD operates at lower and more controllable temperatures, potentially reducing energy use while making it easier to manufacture complex components.
The researchers examined how different processing conditions influence the formation of microscopic defects and grain structures within aluminium alloy 4043, a material widely used in manufacturing and engineering applications. Their findings provide new evidence that carefully controlling the thermal conditions during printing can reduce defects and improve the final material structure.
Dr Fan Wu and Dr Wajira Mirihanage, co-authors from the Department of Materials at The University of Manchester said: “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.”
Metal additive manufacturing is attracting increasing attention because it can create complex geometries while reducing material waste. However, many existing techniques involve extremely rapid heating and cooling, which can introduce defects, residual stresses and distortions into the finished part. MMD offers a different approach by depositing aluminium that has already been melted, reducing the intensity of thermal cycling experienced during manufacture.
To understand how the process influences material quality, the team produced aluminium alloy samples using different nozzle and substrate temperatures. They then used advanced microscopy techniques to investigate grain structure, crystallographic orientation and the distribution of microscopic pores inside the printed components. Mechanical testing was also carried out to assess performance.
The researchers found that higher nozzle and substrate temperatures slowed cooling during printing. This led to larger grain structures and increased levels of porosity, tiny voids within the material that can affect performance. In contrast, lower processing temperatures promoted faster cooling, resulting in finer grain structures and fewer defects.
The study also revealed that defect levels and grain size generally decreased as printing progressed through successive layers of a component. This suggests that thermal conditions evolve throughout the build process, influencing how the material solidifies over time. The team identified a strong relationship between grain size and porosity, providing valuable insight into how manufacturing parameters shape material quality.
Despite the presence of some defects, the mechanical properties of the printed components were found to be comparable with those achieved using conventional manufacturing routes. The researchers reported hardness and elastic modulus values that fall within the expected range for aluminium alloy 4043, highlighting the practical potential of the technology.
Dr Fan Wu and Dr Wajira 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 researchers believe the findings will help accelerate the development of molten metal deposition for industrial applications where component quality, consistency and efficiency are critical.
MMD has been developed by ValCUN BV, a Belgium based manufacturer focused on developing deployable and affordable metal additive manufacturing.
Journal: Materials & Design
Full title: Microstructural evolution and defect formation in aluminium alloy 4043 during molten metal deposition
DOI: 10.1016/j.matdes.2026.116508
URL: https://doi.org/10.1016/j.matdes.2026.116508
Materials & Design
Experimental study
Microstructural evolution and defect formation in aluminium alloy 4043 during molten metal deposition
25-Jun-2026