TY - CONF A1 - Yang, Chunliang A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Experimental and numerical study on grain refinement in electromagnetic assisted laser beam welding of 5754 al alloy T2 - Proceedings of the ICALEO 2023, 42ndt International Congress on Applications of Lasers & Electro-Optics N2 - Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase of the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are analyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain size after welding verifies the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains that have been solidified and formed previously from further growth and generates some small cellular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement. T2 - International Congress of Applications of Lasers & Electro-Optics 2023 CY - Chicago, USA DA - 16.10.2023 KW - Laser beam welding KW - Magnetic field KW - Crystal branch development KW - Grain refinement KW - Periodic solidification pattern PY - 2023 SP - 1 EP - 10 AN - OPUS4-58809 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yang, Chunliang A1 - Wu, Chuansong A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical analysis of ultrasonic vibration enhanced friction stir welding of dissimilar Al/Mg alloys T2 - Mathematical Modelling of Weld Phenomena 13 N2 - The ultrasonic vibration enhanced friction stir welding (UVeFSW) process has unique advantages in joining dissimilar Al/Mg alloys. While there are complex coupling mechanisms of multi-fields in the process, it is of great significance to model this process, to reveal the influence mechanism of ultrasonic vibration on the formation of Al/Mg joints. In this study, the acoustic-plastic constitutive equation was established by considering the influence of both ultrasonic softening and residual hardening on the flow stress at different temperatures and strain rates. And the ultrasonic induced friction reduction (UiFR) effect on friction coefficient in different relative directions at the FSW tool-workpiece interface was quantitatively calculated and analyzed. The Al/Mg UVeFSW process model was developed through introducing the above acoustic effects into the model of Al/Mg friction stir welding (FSW). The ultrasonic energy is stronger on the aluminum alloy side. In the stirred zone, there is the pattern distribution of ultrasonic sound pressure and energy. The heat generation at the tool-workpiece contact interface and viscous dissipation were reduced after applying ultrasonic vibra-tion. Due to the UiFR effect, the projection of friction coefficient and heat flux distributions at the tool-workpiece interface present a "deformed" butterfly shape. The calculated results show that ultrasonic vibra-tion enhanced the material flow and promoted the mixing of dissimilar materials. T2 - 13th International Seminar Numerical Analysis of Weldability CY - Seggau, Austria DA - 04.09.2022 KW - Friction stir welding KW - Ultrasonic vibration KW - Al/Mg alloys KW - Numerical simulation PY - 2023 SN - 2410-0544 VL - 13 SP - 517 EP - 538 PB - Verlag der Technischen Universität Graz AN - OPUS4-58805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -