One-Step Aging Behavior of 7A52 Aluminum Alloy Laser Welded Joint

One-step aging behavior of the 7A52 aluminum alloy laser welded joint was characterized by mechanical property test, electrical conductivity test, EDS and TEM. Results show that the base metal and the weld joint of the 7A52 aluminum alloy need almost the same time to reach peak hardness at different temperatures. When the aging temperature increases from 120 degrees C to 160 degrees C, the age hardening speed of the joint is obviously accelerated and the time to peak hardness is significantly reduced. After aging at 140 degrees C for 16 h, the tensile strength, mass loss and electrical conductivity of the joint are 351 MPa, 0.0070 g/min and 21.1 mS/m, respectively. Compared with the data after aging at 120 degrees C for 24 h, the tensile strength of the joint decreases by 1.13%, the mass loss increases by 2.94% while the conductivity increases by 12.2%. Thus aging at 140 degrees C for 16 h is considered as a reasonable one-step aging process. The precipitate phases of both the welded joint and the base metal are MgZn2. At 140 degrees C, the precipitate phase increases and coarsens with increasing aging time, and the main strengthening phases are n' phase (MgZn2) and GP zone at the peak aging state.