Two-stage aging behavior of pulse variable polarity plasma arc welding joint of 7075 aluminum alloy

Two-stage aging behavior of pulse variable polarity plasma arc welding (PVPPAW) joint of 7075 aluminum alloy with thickness of 10 mm was studied by mechanical properties, electrical conductivity test and TEM analysis, and the reasonable two-stage aging process was determined. Results show that the tensile strength of 7075 aluminum alloy PVPPAW joints increases first and then decreases with the increase of second-step aging temperature and time. After second-step aging with 160℃/12 h, the tensile strength of joint is 545.1 MPa, which increases by 37% than as-weld. And the conductivity is 27.9%IACS, the resistance to stress corrosion is improved than as-weld. The main strengthening phases of the weld center are η' phase and η phase. The precipitated phases of grain interior and grain boundary grow up and become coarsened gradually, and the precipitated free zone in the grain boundary becomes wider with the increase of the second-step aging temperature and time.