The laser-matter interaction and bur phenomena associated with lase processing remain unclear, slowing its process development and optimization. Here, through in situ CCD imaging and mathematical model, we revealed the underlying physical mechanism of bur formation during millisecond pulsed laser processing metallic material. The result shows that the laser-induced gas/vapour jet promotes the flow of melt, and the dynamic behavior of up flow melt along the hole wall is responsible for bur formation; another more, the oxidation phenomena of metallic material have positively influence in bur diminution.
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