Laser additive manufacturing, or LAM (a form of 3D printing in metal using lasers), has ever increasing promise as a fast-duplication, low-waste production method for high-tech precision machinery. As it is used to make complex models such as aerospace components, prosthetics, and even dental structures, scientists and manufacturers are keen to push the limits of this technique.

The challenge we face with LAM is that the laser-matter interaction and solidification phenomena associated with it still remain unclear. This issue hinders the development of LAM because without being able to see the underlying physical phenomena, we are unable to improve the method.

However, this has now changed. A recent experiment involving a group from the EPSRC funded MAPP Hub based in the Research Complex at Harwell (University of Manchester), Diamond Light Source Ltd, and the Central Laser Facility has shed new light onto additive manufacturing. Using high-speed synchrotron X-ray images at Diamond enables us to see into the heart of a previously opaque process, capturing the metal powder's transformation into solid components at a microsecond timescale. The images show how imperfections can form due to hot gas jets, bubble formation and ejected metal droplets (spatter) that creating voids and discontinuous build in the final components. The team uncovered new mechanisms of pore migration by Marangoni flow, pore dissolution and dispersion during laser melting.

While pores are a problem for any type of 3D printing, they are a particular issue for LAM. These minuscule holes weaken the structure of the 3D printed part. In one day sufficient experiments can be performed to produce a process map that not only shows the conditions required for making an optimal part, but also the mechanisms by which the process fails during other conditions. This should enable us to manufacture stronger laser additive manufactured components for transport and aerospace applications using conditions that are faster and lower cost.

Dr​. Chu Lun Alex Leung from the University of Manchester said about this experiment, “Working at the Research Complex at Harwell has given me a fantastic opportunity to meet and work with the experts in X-ray imaging at Diamond Light source and laser science at the Central Laser Facility. It enabled us to form a unique team to develop novel in situ imaging techniques of laser additive manufacturing. Staff from both facilities are very approachable; they are always willing to share their experience and expertise, playing a key part in this exciting research."

Recognising both the novel insights and key applications of this research which utilised three of the large facilities at Harwell, it has been published in Nature Communications, a cutting edge and widely respected science journal.

To read more, go to: https://www.nature.com/articles/s41467-018-03734-7 ​

[DOI: 10.1038/s41467-018-03734-7]