Research On Mechanical Properties And Microstructure And TIG Welding Technology Of 2219T83 Alloy

At the temperature range of±250?,2219 aluminum alloy possesses high strength to weight ratio,high toughness and excellent processability.It is widely used in the main structure of a liquid rocket propellant tank.The fork ring material of the tank is 2219T83 aluminium alloy.During the triturating of the new generation launch vehicle,after annular rolling,quenching,cold forging and aging treatment,the tensile strength and yield strength of the 2219aluminium alloy were lower than the technical demand in several times.Against the background,the paper mainly investigated the effect of secondary aging treatment on mechanical properties and microstructure of the 2219 forging aluminum alloys.After the alloy carrying out the preferred secondary aging treatment,TIG welding technology research and residual stress tests were carried out,for the2219T83/2219T87 butt joint.According to the aging characteristics of 2219 aluminium alloy,the secondary aging process was studied at 175?and 195?,respectively.The results show that,the strength and hardness of 2219T83 alloy,with unsatisfactory radial mechanical properties,increase first and then decrease with prolonging secondary aging time.Peak age regime corresponds to 175?for 11 hours and 195?for 5 hours,respectively.And the mechanical properties of alloy at the peak aging of 195?are slightly better than those of peak aging at 175?.It was shown that the solute atoms in the matrix of 2219 forging aluminum alloys,with low radial strength,had a certain degree of supersaturation,and the aging precipitation incomplete,by SEM,EDS and TEM analysis and testing.In the range of experimental parameters,after the 2219T83 alloy was treated by secondary aging at 195?for 5 hours,the dispersion degree and distribution density of the?'phase increase.2219T83 alloy obtain better mechanical properties,under the comprehensive effect,which the dispersion degree of precipitate is increasing and grain slightly coarsening.After the secondary aging treatment at 195?for 5 hours,it is obtained excellent mechanical properties to the TIG welded joint,through the research on backing welding and cosmetic welding,with 8mm 2219T83/2219T87 in heterogeneous heat treatment state.The parameters are that,the backing welding current is 230±5A,the welding rate is 17m/h,arc voltage is 14.5±0.3V,the tip diameter of tungsten electrode is 1.5mm,the cosmetic welding current is 330±5V,the welding rate is 9m/h,wire feed rate is 42±3m/h,and arc voltage is 21±0.5V.And it has the properties of low temperature strengthening and toughening.The tensile strength is up to 304MPa,the elongation up to 5.3%at room temperature,the tensile strength is up to 375MPa,the elongation up to 7.5%at the temperature of-196?.For the 2219T83/2219T87 TIG welded joints,uder the better welding parameters,the residual stress on the weld surface was detected by XRD testing method.Distribution of residual stress in longitudinal section of weld center is as follows:the longitudinal stress?_x is tensile stress;the partial stress?_y perpendicular to weld direction is in the arc start-up stage and arc extinction stage,the rest is tensile stress.Meanwhile,the distribution of residual stress,beside the 2219T83 side to the cross section about 120 mm from the arcing end,is as follows:the longitudinal stress?_x is tensile stress in the region,which is from the center of the weld to 25 mm outward,compressive stress in the Test Zone 25-65mm from the weld Center.The partial stress?_y perpendicular to weld direction is tensile stress in the region,which is from the center of the weld to 20 mm outward,compressive stress in the Test Zone 20-65mm from the weld Center.