Abstract:
Butt welding test was carried out on hot-rolled AZ31 magnesium alloy sheets with thickness of 2 mm by TIG (tungsten inert gas) welding at different welding heat inputs. Microstructure and mechanical properties of welded joints were analyzed by using microscope, micro-hardness tester, tensile testing machine and so on. The results show that the microstructure of the base metal is single-phase α-Mg solid solution, and the microstructures of heat affected zone and weld zone are all single-phase α-Mg solid solution and dispersively distributed β-Mg
17Al
12. With the increase of the heat input, the grain size in weld zone grows and the amount of β-Mg
17Al
12 increases. The micro-hardness from large to small is weld zone, base metal zone and the heat affected zone. The tensile strength of welded joints increases firstly, and then decreases with the increase of the heat input. The welded joints owned the best tensile strength of 223 MPa at welding current of 90 A, the value was about 89.2% of the base metal, meanwhile, the elongation was 10.0%.It is founded that the fracture mainly occurres in HAZ and the fracture mode is quasi-cleavage fracture.