SRμCT study of crack propagation within laser-welded aluminum-alloy T-joints

Using laser welding in fabrication of metallic airframes reduces the weight and hence fuel consumption. Currently only limited parts of the airframes are welded. To increase laser beam welded parts, there is the need for a better understanding of crack propagation and crack-pore interaction within the welds. Laser beam welded Al-alloys may contain isolated small process pores and their role and interaction with growing crack need to be investigated. The present paper presents the first results of a crack propagation study in laser beam welded (LBW) Al-alloy T-joints using synchrotron radiation based micro computed tomography (SRμCT). A region-of-interest technique was used, since the specimens exceeded the field of view of the X-ray detector. As imaging with high density resolution at high photon energies is very challenging, a feasibility measurement on a small laser weld, cut cylindrically from the welded region of a T-joint, was done before starting the crack-propagation study. This measurement was performed at the beamline HARWI-II at DESY to demonstrate the potential of the SRμCT as non-destructive testing method. The result has shown a high density resolution, hence, the different Al alloys used in the T-joint and the weld itself were clearly separated. The quantitative image analysis of the 3D data sets allows visualizing non-destructively and calculating the pore size distribution.     «

Using laser welding in fabrication of metallic airframes reduces the weight and hence fuel consumption. Currently only limited parts of the airframes are welded. To increase laser beam welded parts, there is the need for a better understanding of crack propagation and crack-pore interaction within the welds. Laser beam welded Al-alloys may contain isolated small process pores and their role and interaction with growing crack need to be investigated. The present paper presents the first results o...     »