Repeatedly Repair Welding And Welding Process Parameters Effects On Organization And Mechanical Properties Of 5083-H111 Aluminum Alloy Welded Joints

Aluminum alloy,a common metal material,has been massively used in the rail vehicles manufacture industry.But it also brings some trouble for the welding of the vehicles.Since the aluminum alloy has some flaws like high thermal conductivity and thermal expansion coefficient,easy softening,broad HAZ,easy to form pores,cracks and incomplete fusion while welding,selecting proper welding method and number of repairing weld will be an efficient way to limit aluminum alloy welding flaws and improve welded joint properties.The influence on the structure and property of the welded joint on 5083-H111 aluminum alloy board with different thickness under different welding method and numbers of repairing weld has been concluded in this paper by taking tensile test,bending test,metallographic test and microhardness test on MIG welded joint of 5083-H111 aluminum alloy board with the thickness of 4mm and 16mm under different welding method and numbers of repairing weld.The result shows that the tensile strength of all the welded joints under different welding method is satisfied;all the fracture path are at the weld position;the tensile strength of the 4mm welded joint reached the maximum value under small heat input without preheat before welding,while the tensile strength of 16mm welded joint reached the maximum value when using small heat input,preheat temperature is 70⁹0?and interpass temperature is the welding temperature.All the bending angles of the welded joints under different welding methods can reach the point of 180°in the bending test,which reflects a good bending property.Softening phenomenon wasn't detected in any welded joint under different welding methods.The microstructures of the weld point in every welded joint under different welding method are all in the form of equiaxed dendrite,and the microstructures of the HAZ are grains lined along the rolling direction in a fibriform,meanwhile the Mg2Al3 strengthening phases are distributed on??Al?base metal.No obvious columnar crystal appears in the microstructure of the fusion zone of 4mm welded joint under different welding methods. Columnar crystal appears in the microstructure of the fusion zone of 16mm welded joint when using high heat input without preheat and interpass temperature is the room temperature after cooling down.The tensile strength of all the welded joints under different numbers of repairing weld is satisfied;all the fracture path are at the weld position but with the number of repairing weld increases the tensile strength of the welded joint will decrease.All the bending angles of the welded joints under different numbers of repairing weld can reach the point of 180°in the bending test,which reflects a good bending property.Softening phenomenon wasn't detected in any 4mm welded joint under different numbers of repairing weld;the softening phenomenon in the HAZ becomes serious with the number of repair welding increases.The microstructures of the weld point in every welded joint under different numbers of repairing weld are all in the form of equiaxed dendrite,and the microstructures of the HAZ are elongated grains lined along the rolling direction in a fibriform,the component are mainly??Al?base metal and partially separated??Mg₂Al₃?distributed on it.No obvious columnar crystal appears in the microstructure of the fusion zone of 4mm welded joint under different numbers of repairing weld.Columnar crystal becomes obvious and thicker as the repairing weld number increases.