2219铝合金TIG和FSW接头力学及疲劳性能

目的 研究钨极氩弧焊(TIG)和搅拌摩擦焊(FSW)对2219铝合金(母材)力学及疲劳性能的影响。方法 通过拉伸试验,得到了母材、TIG和FSW接头的抗拉强度和伸长率;通过疲劳性能试验测试了母材、TIG和FSW接头在不同应力下相应的疲劳寿命,根据疲劳试验结果绘制了其试样的S-N曲线;使用扫描电子显微镜观察并分析了疲劳断口的形貌特征。结果 未焊接的铝合金母材抗拉强度和伸长率最高,分别为506 MPa和15.92%;TIG接头抗拉强度和伸长率分别为330 MPa和7.65%,FSW接头抗拉强度和伸长率分别为310 MPa和8.74%。母材、TIG和FSW接头等3种疲劳试样在2×10⁶次循环下的疲劳强度分别为129、108、115 MPa,其疲劳断口均可分为裂纹源区、裂纹扩展区和瞬间断裂区,疲劳裂纹分别起始于试样表面的局部变形区、第二相夹杂物和“吻接”缺陷。疲劳裂纹扩展区的主要形貌为疲劳辉纹和二次裂纹,瞬间断裂区以脆性断裂为主。结论 TIG和FSW等2种焊接工艺均导致了2219铝合金的强度、塑韧性和疲劳性能降低,其接头表面的第二相夹杂物和“吻接”缺陷促进了疲劳裂纹的萌生。

Mechanical Properties and Fatigue Properties of 2219 Aluminum Alloy TIG Joints and FSW Joints

The work aims to study the effects of TIG and FSW on the mechanical properties and fatigue properties of 2219 aluminum alloy. The tensile strength and elongation of three specimens (BM, TIG and FSW joints) were tested through tensile test. The fatigue life of the three specimens under different stresses was tested by fatigue test. According to the results of fatigue test, S-N curves of the three specimens were drawn, and the morphology characteristics of the fatigue fracture were observed and analyzed by SEM. The tensile strength and elongation of unwelded aluminum alloy were the highest, which were 506 MPa and 15.92% respectively, The tensile strength and elongation of TIG joint were 330 MPa and 7.65% respectively. The tensile strength and elongation of FSW joint were 310 MPa and 8.74% respectively. For three specimens, the fatigue strength at 2×106 cycles was 129, 108 and 115 MPa respectively. The fatigue fracture surfaces of the three specimens can be divided into crack source, crack propagation area and transient fracture area. The fatigue cracks of the three specimens originated from the local deformation area, second phase inclusions and "kissing" defects on the surface of the sample, respectively. The main morphology of fatigue crack growth area was fatigue striation and secondary crack, and the transient fracture area was mainly brittle fracture morphology. Both TIG and FSW processes reduce the strength, plastic toughness and fatigue performance of 2219 aluminum alloy. The second phase inclusions and "kissing" defects on the joint surface promote the initiation of fatigue cracks.