Identification of the influence of mechanical vibrations on the solidification process during deep penetration welding

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Mechanical vibrations can significantly influence the grain growth during solidification of liquid metals. This effect is used as a mechanical refinement method and is well established in casting technology. Using this method in deep penetration laser beam welding process within a frequency range of 0 Hz to 5 kHz has also shown a beneficial impact to the grain structure in the fusion zone. However, the main influencing factors and mechanisms behind this refinement effect are not completely understood in the case of the comparatively fast deep penetration laser beam welding. Within the scope of this research project this mechanisms and factors shall be determined by means of experimental investigations. The main assumption is that the refinement effect is more efficient for comparatively high frequencies and is mainly based on grain detachment due to the additional relative movement between the melt pool and the solidification front. Knowing the main influencing factors of this effect can provide a basis for the future development of efficient system technologies capable to produce a finer grain microstructure and hence improved weld seam properties, especially reducing the occurrence of hot-cracking.