Study On Microstructure And Properties Of TIG And Laser Welding Joints Of TA10/Q345 Bimetallic Plate

As a new type of structural material,titanium/steel bimetallic plate has not only excellent corrosion resistance of titanium but also high strength and high elastic modulus of structural steel.The special thermophysical and chemical properties of titanium and titanium alloys may lead to the occurrence of welding defects in the welding process of titanium/steel composite plates.In combination with TIG welding and laser welding processes,the effects of different filler materials and welding methods on the microstructure and properties of the weld were studied.In combination with thermal simulation experiments,the effect of different thermal cycling conditions on the microstructure and properties of the heat-affected zone was investigated to provide theoretical guidance for the actual welding process.Results of TIG welding test:Copper-coated ER50-6 and TA10 welding wire were used as the filler material.The different of weldablitily results in microcracks.The hardness values near the crack were 1144.7HV_0.2 and 1083.7HV_0.2,respectively.Copper-coated ER50-6 and pure copper wire were used as the filler material.The TiCu₂ low-melting point eutectic formed by the peritectic reaction between excess TiCu and the remaining liquid phase during cooling can easily cause welding hot cracks.Copper-coated ER50-6,pure copper and TA10 wire were used as the filler material.There was still microcracks between the pure copper filled layer and the base layer Q345 steel.The weld structure was mainly composed of copper matrix and dispersed mesophase grains.Excess copper dissolved in steel during the process.The particulate?+?duplex formed by the diffusion of iron is a brittle structure and is the main cause of microcracks.Too much melting of copper will reduce the strength of the weld.Too little of the amount of melting will not dilute the Ti-Fe intermetallic compound.Results of laser welding test:Laser welding was performed directly on the TA10 titanium alloy.A large temperature gradient results in uneven distribution of the microstructure.The center of the weld is a thick equiaxed crystal.The microstructure of the heat-affected zone consists of equiaxed?-phase and acicular martensite.The fusion of the two sides of the fusion line is not uniform.There is easy to stress concentration where cracks easily sprouted here.In the welded joint of pure copper sheet as the filler material,the titanium/steel/copper three-phase fusion zone exists at the titanium/steel interface.Compared to TIG welding,laser welding does not directly heat the TA10 titanium alloy by welding.The diffusion distance of the elements near the fusion line is short,which is conducive to avoid the formation of excessive intermetallic compounds.The diffusion distance from the copper to the titanium side is short.Cu-Ti compounds exist only near the interface and on the copper side.The weld has good overall performance.The results of thermal simulation tests show that the higher the peak temperature of the heat affected zone,the thicker the interfacial microstructure of the explosion-welded composite plate.And the number of martensite needles.When the temperature is lower than the phase transition temperature of 884°C,the diffusion process is slowed down by?-Ti transforms into?-Ti,forming a lamellar structure.Rapid cooling from above the martensitic phase transition temperature,resulting in the formation of fine disc-like or needle-like martensite structure.The microhardness at the interface increases with the increase of the peak temperature.The main reasons for the increase of microhardness are the Ti-Fe compound formed during the explosive welding process at the interface,the dislocations not being able to diffuse and the acicular martensite formed during rapid cooling.