A6N01铝合金焊接接头的微观组织与力学性能

Microstructures and mechanical properties of A6N01 aluminum alloy welding joint

对高速列车车体用新型A6N01铝合金进行MIG焊接,使用光学金相(OM)、扫描电镜(SEM)、透射电镜(TEM)、显微硬度计和拉伸试验机对焊接接头的显微组织与力学性能进行观察与分析。结果表明:焊缝金属为等轴晶状的铸态组织,焊缝边缘的熔合区形成柱状晶组织。在热影响区(HAZ),过时效区的晶粒比淬火区的更为粗大,形成HAZ软化区。A6N01铝合金母材析出短棒状β′(Mg2Si)过渡强化相。HAZ析出粗大的短棒状稳定强化相β(Mg2Si)。焊缝显微硬度最低,约为65 HV。焊接接头的抗拉强度为270 MPa,断后伸长率为6.0%。

The new type A6N01 aluminum alloy used in the high-speed vehicles was welded by MIG welding. The microstructures and mechanical properties of the welding joints were observed and analyzed by OM, SEM, TEM, microhardness and tensile testers. The results show that equiaxial as-cast rnicrostructures exist in the welding metal. The columnar grains are formed in the fusion zone next to the welding seam. In the heat-affected zone （HAZ）, the grains of over-aging zone are coarser than those of quenching zone. The softening region exists in the over aging zone of HAZ. The β＇（Mg2Si） transitional strengthening phases precipitate in A6N01 aluminum alloy base metal. The β＇ phase presents claval shape. The β（Mg2Si） stable strengthening phases precipitate in HAZ, which present coarse claval shape. The mierohardness of welding seam is the lowest in the joint, which is about 65 HV. The tensile strength of the joint is 270 MPa, and the elongation after fracture is 6.0%.