A joint research team from the University of Birmingham, UK, Stockholm University, Sweden and Zhejiang University, China has finalised a new technique thanks to which 3D print metals, involving a widely used stainless steel, achieve exception levels of both strength and ductility, compared to those subjected to more conventional processes.

The research challenges the existing skepticism about the ability to produce strong and ductile metals through 3D printing, recognized as a technology which can potentially change our way of manufacturing, allowing us to quickly build up objects with complex and customized geometries.
With the accelerating development of the technology in recent years, 3D printing, especially metal 3D printing, is quickly progressing toward widespread industrial application.
Despite the bright future, the quality of the products from metal 3D printing has been prone to scepticism. In most metal 3D printing processes, products are directly built up from metal powders, which makes it susceptible to defects, thus causing deterioration of mechanical properties.

The research findings, published in Materials Today, outline how to produce the next generation of structural alloys with significant improvements in both strength and ductility. This has been made possible thanks to the ultrafast cooling rate, estimated to range from 1000 °C per second to 100 million °C per second.
Metals that are cooled down so quickly result in a so-called non-equilibrium state, allowing for some amazing microstructures like the sub-micro-sized dislocation network — which was revealed in this paper to be the main reason of the improved mechanical properties.
Ultimately, this dislocation network means greater flexibility for engineers who need complex metal shapes which are not necessarily rigid or fragile.

Dr. Leifeng Liu, who is the main participant of the project, said: “This work gives researchers a brand new tool to design new alloy systems with ultra-mechanical properties. It also helps metal 3D printing to gain access into the field where high mechanical properties are required like structural parts in aerospace and automotive industry.”