Research On The Properties And Deformation Control Of Thick 2A12 Aluminum Alloy Electron Beam Welded Joints

2A12 aluminum alloy,belonging to aluminum-copper-magnesium series heat-treatable aluminum alloy,is one of the most widely used deformed aluminum alloys in China.2A12 high-strength aluminum alloy with light quality,good corrosion resistance,high specific strength and specific stiffness,excellent electrical conductivity and thermal conductivity,as well as other comprehensive properties,compared with steel materials,can significantly reduce the weight of structural parts and was widely used in aerospace,defense and other fields.In this paper,electron beam welding(EBW)of 2A12 thick aluminum alloy plate was investigated to provide theoretical basis for practical application.Obvious collapse defects appear on the top of 2A12 aluminum alloy after electron beam welding.And the spatter was larger in the welding process.These defects can be significantly improved by adding a process liner to the bottom of the specimen.It can achieve the double-sided forming,making the weld uniform and continuous.After welding process,microstructure of the joint was coarsened,the heat-affected zone is obvious columnar crystal structure.Under the scanning and stirring effect of EB,equiaxed crystals was generated in the weld and some rose-like microstructures was detected.Ultrasonic impact treatment can refine the microstructure of the joint surface,and the thickness of the deformation layer is 170?m.The main strengthening phase in the joint after welding changed from S phase(Al2Cu Mg)to the S(Al2Cu Mg)+(Al2Cu)phase.After welding process,2A12 aluminum alloy showed obvious joint softening,the hardness of the weld zone was 120 HV,which was 80% of the base metal,and with the increase of penetration depth,the hardness of the weld zone gradually raised.A clear hardened area,with a maximum hardness of 450 HV,was formed at the bottom of Cu gasket joints.Ultrasonic impact treatment can increase the surface hardness of the joint,which is basically equivalent to that of the parent metal.The overall tensile strength of the joint is 360 MPa,which is 80% of that of the base metal,and the weak area at the bottom of the joint is only 264 MPa.The Al-Cu compound was formed at the bottom of the Cu gasket joint,which significantly decreased the performance of the joint.The corresponding tensile strength was only 200 MPa,44% of the base metal.The residual stress and deformation of the joint were analyzed by numerical simulation and practical measurement.The welding constraint fixture was introduced into the numerical simulation of the welding process,which provided a theoretical basis for the welding deformation control of the cylinder specimen.The simulation results show that the welding deformation of the specimen were 0.175 mm to 0.45 mm with restraint,the residual stress of the specimen increased from 305 MPa to 362 MPa after binding.The test of the welding deformation showed that the transverse shrinkage deformation occurred when the sample was welded under the free state and the deformation was 0.4mm.The welding deformation was controlled by the rigid fixing method,the welding deformation of the specimen was reduced to 0.2mm,and the fitting degree is higher with the simulation result.The welding deformation was reduced by 50%.The residual stress was controlled by the method of ultrasonic impact treatment.The pressure field of the pressure field is about 150 MPa.