Microstructure and tensile property of the joint of Laser-MIG hybrid welded thick-section TC4 alloy

In this paper, thick-section TC4 alloy was welded to itself by laser-MIG hybrid (LAMIG) welding. The microstructure of the welded joints was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed that α’ and β phases were formed in the weld seam. The effects of heat input (E) on the microstructure and tensile strength of the joints were investigated. With the increase of heat input, the residence time of platelet α’ martensite in the high-temperature phase changing zone became longer and the thickness of platelet α’ martensite increased. Furthermore, the β thickness became large, and tangling dislocations were found to exist in platelet α’. In addition, the increasing heat input could cause a decrease in the tensile strength. The failed dimple pattern experienced a change from equiaxed to tearing, which was harmful to the property of the joint.