5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Solidification phenomena during laser additive manufacturing (LAM) occur under rapid solidification conditions, with the entire melting and solidification process occurring in a few milli-seconds. New characterisation techniques are required to capture the powder-melting, weld pool formation, together with the subsequent solidification phenomena including defect formation. To enable this, a laser additive manufacturing process replicator (LAMPR) was designed and commissioned that performs full LAM builds in situ and operando on a synchrotron beamline. This enables imaging of the process in real and reciprocal space at ultra-fast speeds (up to 50,000 frames per second) and high resolutions (ca. 1 microns). Dozens of layers can be built with hatching in each layer, whilst capturing the laser-powder interactions, including melting and the formation of spatter caused by combined metal vaporisation and argon gas heating. During track formation, we observe the mechanisms by which contiguous track is formed, and when beading occurs and why. The different types of porosity formation are also observed and quantified, suggesting ways of avoiding their formation. Finally, the processing space is explored for an SS316 powder, and a mechanistic processing map is produced which not only quantifies the processing window, but also shows the mechanisms which limit operation to within this window, and hence how the window can be expanded to produce higher strength components more efficiently.