Fracture behavior of double-pass TIG welded 2219-T8 aluminum alloy joints under transverse tensile test
(1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;
2. Key Laboratory for Advanced Materials Processing Technology, Ministry of Education,
Tsinghua University, Beijing 100084, China;
3. School of Aerospace, Tsinghua University, Beijing 100084, China;
4. Beijing Institute of Astronautics Systems Engineering, Beijing 100076, China)
2. Key Laboratory for Advanced Materials Processing Technology, Ministry of Education,
Tsinghua University, Beijing 100084, China;
3. School of Aerospace, Tsinghua University, Beijing 100084, China;
4. Beijing Institute of Astronautics Systems Engineering, Beijing 100076, China)
Abstract: 2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas (TIG) arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zone (PMZ). Effects of the PMZ on the fracture behavior were systematically studied. Continuous intergranular eutectics were observed in the PMZ close to the fusion line. Away from the fusion line, the intergranular eutectics in the PMZ became discontinuous. The fracture morphology and the microhardness distribution of the joint showed that the PMZ was gradient material with different mechanical properties, which strongly affected the fracture process. It was observed that the crack initiated in the PMZ near the front weld toe, and propagated in the PMZ away from the fusion line. Then, the crack tip was blunt when it propagated into the PMZ with higher plasticity. Finally, the rest part of the joint was shear fractured.
Key words: 2219 aluminum alloy; tungsten inert gas arc welding; partially melted zone; fracture behavior