| Aluminium alloy is widespreadly used in aviation structure. A new aluminiumalloy T-shape structure manufacturing thought is put forward to lower processing costin this paper. Weld zone and HAZ of aluminium alloy would softened while welding,artificial aging treatment was employed to re-strengthen aluminium alloy structure,and overall performance assessments of welded structure were carried out after agingtreatment.Firstly, effects of aging to mechanical property of butt joint was studied. Grain ofweld zone is fine and even and grew after aging, leading to descend of plasticity.Hardness of base metal is139HV, and weld zone softened seriously, the hardnessonly was69HV. The problem was improved effectively after aging. Hardnessdistribution was even and achieved to132HV. Tensile test and appearance of fractureanalysis was carried out. Tensile strength of base metal is443MPa, elongation is12.6%and it was ductile fracture. Tensile strength of welding joint is241MPa, elongation is5.8%. Tensile strength of joint increased to362MPa after aging, elongation is5.8%and it was brittle rupture. Impact toughness of base metal, welding joint and agedwelding joint were12.9J/cm~2,9.2J/cm~2and14.2J/cm~2respectively. In conclusion,mechanical property was entirely improved after artificial aging.Then pitting corrosion test and intergranular corrosion test were applied toinvestigate the influence of aging treatment after welding on the corrosion resistance2219aluminium alloy welding structure. Pitting resistance across the thickness ofrolling plate is poor and the pit distributed uniformity. Weld seam and HAZ generatedpit hardly since of overaging. While pitting susceptibility of the zone remote from theweld-seam increased because of different levels of Al2Cu solution. Weld joint wouldpossess good corrosion resistance after aging. However the pitting susceptibilityincreased seriously if defects existed in weld-seam. The resistance to intergranularcorrosion of base metal is fine. Serious intergranular corrosion occured in weld-seamand HAZ, and maximum corrosion depth is379μm in HAZ. Intergranular corrosionwas also existed in weld-seam and HAZ after aging and maximum corrosion depth is200μm in weld-seam. Thus, intergranular corrosion susceptibility of welding jointwas highest. The two principal influencing factor of fatigue life of T-joint are stressconcentration in weld toe and residual stress of welding joint. The greater knuckleradius of joint was, the lower concentration factor was and the longer the fatigue lifewas. Fatigue strength of welded T-joint was71MPa. And the fatigue strength of theaging welded T-joint was89MPa, which increased by26%. In conclusion, the fatiguelife improved after artificial aging because of the release of residual stress andrecovery of strength. |
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