7A52铝合金激光焊接头单级时效行为

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

通过力学性能、电导率测试、EDS分析和TEM分析,对7A52铝合金激光焊接头单级时效行为特征进行了研究,并确定了较为合理的单级时效工艺。结果表明,7A52铝合金激光焊焊缝和母材在不同温度下达到峰值硬度所需要的时间基本是一致的,当时效温度由120上升到160℃时,接头时效硬化速度明显加快,达到峰时效时间明显缩短。与120℃时的峰时效状态相比,经140℃,16h时效处理后的接头抗拉强度为351 MPa,失重量为0.0070g/min,电导率为21.2mS/m,接头抗拉强度下降了1.13%,失重量增加了2.94%,电导率却提升了12.2%,综合考虑以140℃保温16h单级时效工艺为宜。焊缝和母材的析出相均是相,随时效时间的延长析出相逐渐增多粗化,且峰时效状态下的起主要强化作用的是η′相和GP区。

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℃ to 160 ℃, the age hardening speed of the joint is obviously accelerated and the time to peak hardness is significantly reduced. After aging at 140 ℃ for 16 h, the tensile strength, mass loss and electrical conductivity of the joint are 351 MPa, 0.0070 g/rain and 21.1 mS/m, respectively. Compared with the data after aging at 120 ℃ 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 ℃ 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 ℃, the precipitate phase increases and coarsens with increasing aging time, and the main strengthening phases are η＇ phase （MgZn2） and GP zone at the peak aging state.