焊后热处理对7075铝合金脉冲MIG补焊接头组织和力学性能的影响

Effect of post weld heat treatment on microstructure and mechanical properties of pulse MIG repairing weld joint of 7075 aluminum alloy

针对7075铝合金MIG焊对接接头,采用脉冲MIG焊进行补焊,之后对接头分别进行T6、T7和RRA三种焊后热处理。对3种焊后热处理接头和未热处理接头的组织和力学性能进行了对比分析。结果表明：焊后热处理有效改善了焊缝和热影响区的组织,T7热处理后焊缝和热影响区晶粒细小,冲击吸收能量最高,塑性最好;T6热处理接头具有最高的抗拉强度,达到400 MPa,较未热处理提高了25%;RRA热处理后力学性能处于T6和T7之间;3种热处理均提高了母材区的硬度,而且热影响区的硬度也提高到与母材相当;但焊后热处理对补焊焊缝区的硬度提高不明显。

7075 aluminum alloy MIG welded joints were repairing welded by pulse MIG welding process,and microstructure and mechanical properties were investigated after T6,T7 and RRA post weld heat treatment（ PWHT）. The results show that microstructure in the weld metal（WM） and heat affect zone（HAZ） are improved effectively after PWHT. T7 PWHT joints have the highest impact absorbed energy and plasticity due to the fine grain in the WM and HAZ. T6 PWHT joints have the highest tensile strength,about 400 MPa,increase 25% than that of unheated treatment. Mechanical properties of the RRA are in the range of T6 and T7. The three PWHT improve the hardness of base metal（ BM）. And hardness of the HAZ is improved as high as the BM,but the hardness of the WM is not improved obviously by three PWHT.