Institute of Transport and Automation Technology Research Publications
In Situ Observation of Solidification Conditions in Pulsed Laser Welding of AL6082 Aluminum Alloys to Evaluate Their Impact on Hot Cracking Susceptibility

In Situ Observation of Solidification Conditions in Pulsed Laser Welding of AL6082 Aluminum Alloys to Evaluate Their Impact on Hot Cracking Susceptibility

Categories Zeitschriften/Aufsätze (reviewed)
Year 2015
Authors von Witzendorff, P.; Kaierle, S.; Suttmann, O.; Overmeyer, L.
Published in Metallurgical and Materials Transactions A April 2015, Volume 46, Issue 4, pp 1678-1688, Springer Boston
Description

The influence of laser pulse parameters on solidification conditions and hot crack formation in pulsed laser welding of Al6082 aluminum alloys was studied with the aid of high-speed cameras capturing visible and infrared radiation. Hot cracking was evaluated with respect to strain rate, strain, and metallurgical outcome. The strain rate was approximated by the product of interface velocity and temperature gradient at the interface. The temperature gradient decreases during the course of solidification and followed a specific course. The interface velocity was therefore used as an indicator for the strain rate, which increased in a logarithmic manner with respect to the slope of the laser pulse's cooling time. The accumulated strain was calculated by measuring the spot weld deformation during solidification. Within the heat-conduction welding regime, hot cracking can be reduced by lowering the interface velocity leading to a reduced strain rate and enhanced permeability of the dendritic microstructure. An over-proportional increase of the accumulated strain was observed for keyhole welding, which led to a high susceptibility to hot cracking regardless of the interface velocity. At low interface velocities, hot cracking was induced by extensive hydrogen diffusion at the solid-liquid interface, which promotes crack initiation.

[384]

DOI 10.1007/s11661-015-2749-z