To better understand the laser drilling process and especially to clarify keyhole dynamics in metal drilling, a quasi-two-dimensional drilling assembly was set up with a thin sandwich structure. Keyhole dynamics coupling multiple physical processes were recorded using highspeed photography, and clear images were obtained. The formation of keyholes was found not to be a single unified process, and the whole drilling process could be divided into five stages: an initial melt ejection, mild melting, rapid drilling, hole expansion, and backflow and recasting. As the keyhole evolved, the removal of material changed. [http://dx.doi.org/10.1063/1.4829147]

The article was published as:
Chen M,Wang YR,Yu G,Lan D,Zheng ZY. In situ optical observations of keyhole dynamics during laser drilling. APPLIED PHYSICS LETTERS, 2013, 103(19):194102/1-194102/4, doi: 10.1063/1.4829147