TY - JOUR N2 - Plates of AZ91 cast magnesium alloy with a thickness of 3.5 mm were butt-welded using a laser power of 2000 W and helium as the shielding gas. The effect of the welding speed on the weld cross-sectional geometry and porosity was determined by microscopic analysis. It was found that to avoid the formation of macropores, welding should be carried out at a speed of 3.4 m/min or higher. Non-equilibrium solidification of the laser-melted metal causes fragmentation of the weld microstructure. Joints that were welded at optimal laser processing parameters were subjected to structural observations using optical and scanning microscopy and to mechanical tests. The mechanical properties were determined through Vickers hardness measurements in the joint cross-section and through tensile testing. The results indicate that the hardness in the fusion zone was about 20 HV (30%) higher than that of the base material. The weld proved to be a mechanically stable part of the joint; all the tensile-tested specimens fractured outside the fusion zone. L1 - http://www.journals.pan.pl/Content/116480/PDF/AFE%203_2020_02.pdf L2 - http://www.journals.pan.pl/Content/116480 PY - 2020 IS - No 3 EP - 14 DO - 10.24425/afe.2020.133322 KW - AZ91 alloy KW - Laser welding KW - Porosity KW - Microstructure KW - Mechanical properties A1 - Dziadoń, A. A1 - Musiał, E. PB - The Katowice Branch of the Polish Academy of Sciences VL - vol. 20 DA - 2020.06.01 T1 - Structure and Mechanical Properties of the CO2 Laser Welded Joint of AZ91 Cast Magnesium Alloy SP - 9 UR - http://www.journals.pan.pl/dlibra/publication/edition/116480 T2 - Archives of Foundry Engineering ER -