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Please note that all times are shown in the time zone of the conference. The current conference time is: 4th Aug 2021, 02:24:45am CEST
Aluminum die casting alloys are frequently used in the automotive industry for front and rear rails, corner nodes and interface blocks to weld together varying cross sections of aluminum extrusions in lightweight chassis structures. However, these materials have limited weldability due to entrapped gases which generate pores or cavities. Therefore, the thermal cycle during welding as well as the overall heat balance need to be carefully controlled in order to reduce the porosity level and hence achieve the desired joint integrity. This paper focuses on the selection of process parameters for the material combination of Al die casting C611 to Al extrusion AA6063. Results showed that the porosity level can be significantly reduced from 5-6% to below 2% of the weld area through the combination of beam oscillation and dual beam welding with Adjustable Ring Mode laser. Additionally, the selected parameters resulted in an average ultimate tensile strength of 120 MPa.
10:15am - 10:30am
Analytical approach for the transition to an equiaxed dendritic solidification during laser beam welding of aluminium alloys
Constantin Böhm1, Yassin Nasr1, Jonas Wagner2, Christian Hagenlocher2, Stefan Weihe1
1University of Stuttgart, Materials Testing Institute (MPA), Pfaffenwaldring 32, 70569 Stuttgart, Germany; 2University of Stuttgart, Institut für Strahlwerkzeuge (IFSW), Pfaffenwaldring 43, 70569 Stuttgart, Germany
An equiaxed solidification in a laser beam welded seam is beneficial. It leads to grain refinement, which increases mechanical strength and hot cracking resistance. The effects of filler wire addition and welding parameters on the resulting grain structure are experimentally well studied. Up until now, there has been no description of the process window for equiaxed solidification in terms of the process parameters. This work presents an analytical approach to access the description of the columnar-to-equiaxed transition based on fundamental solidification theory for a wide-range of aluminium alloys and laser welding parameters. To validate the approach, the theoretically calculated powers are compared to experimental results of full penetrated weld seams. This study provides an overview of the key process parameters and the material characteristics, which determine the solidification mode – in this case columnar or equiaxed dendritic. Furthermore, a process window for grain refinement of aluminium alloys is derived.
10:30am - 10:45am
High-speed synchrotron X-ray investigation of full penetration welding of aluminum sheets
Jonas Wagner1, Christian Hagenlocher1, Marc Hummel2, Alexander Olowinsky3, Rudolf Weber1, Thomas Graf1
1Institut für Strahlwerkezuge (IFSW), Universität Stuttgart, Germany; 2Chair for Laser Technology LLT, RWTH Aachen University, Germany; 3Fraunhofer Institute for Laser Technology ILT, Aachen, Germany
Full penetration laser beam welding of aluminum alloys is widely applied in industrial welding processes of sheet metal components. It is characterized by a capillary, which fully penetrates two or more sheets in overlap configuration and is open at its top and bottom. Compared to partial penetration laser beam welding, full penetration welding is associated with a stable capillary and therefore a more reliable process because the additional opening at the bottom side results in the avoidance of a collapsing capillary tip. The behavior of the capillary was analyzed by means of high-speed X-ray imaging at the DESY-synchrotron for welding of aluminum sheets with thicknesses of 1 mm and 2 mm. The results prove the stabilization of the capillary if it opens at the bottom side of the sheet. Despite the reliable avoidance of capillary collapses, the formation of pores is still observed.