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采用显微硬度和拉伸性能测试对比了激光-单丝脉冲MIG复合焊和MIG焊接的4 mm厚A6N01-T5铝合金板接头的力学性能。通过高周疲劳测试、疲劳裂纹扩展速率试验以及疲劳断口分析,探讨了激光-MIG复合焊接头的疲劳性能和断裂行为。结果表明,与母材相比,复合焊接头和MIG焊接头焊后均发生强度损失现象,且MIG焊接头的损失程度更为严重。复合焊接头疲劳寿命随应力幅的增加而减小,且同一应力幅下,寿命分布具有分散性,50%存活率下A6N01铝合金复合焊接头的疲劳强度为104 MPa,为母材(117 MPa)的88.9%。A6N01铝合金母材和复合焊接头的da/d N-ΔK曲线存在交叉现象,当ΔK<18.63 MPa·m~(1/2)时,焊缝的裂纹扩展速率慢于母材,认为可以安全可靠地进行服役。复合焊接头疲劳裂纹由加工缺陷处萌生,裂纹源区呈现类解理河流花样;裂纹稳定扩展区未发现疲劳条带;瞬断区存在大小不一的韧窝和较为尖锐的撕裂棱,呈现准解理断裂和韧性断裂的混合断裂形式。
The mechanical properties of 4 mm thick A6N01-T5 aluminum alloy plate joints with laser-monofilament pulsed MIG composite welding and MIG welding were compared with the microhardness and tensile tests. Through the high-cycle fatigue test, fatigue crack growth rate test and fatigue fracture analysis, the fatigue performance and fracture behavior of laser-MIG composite welding head were discussed. The results show that compared with the base metal, the strength loss occurs both after the composite welding head and the MIG welding head are welded, and the loss of the MIG welding head is more serious. The fatigue life of the composite welded joint decreases with the increase of the stress amplitude, and the distribution of life span is dispersive under the same stress amplitude. The fatigue strength of A6N01 aluminum alloy composite welded joint is 104 MPa at 50% ) Of 88.9%. The da / d N-ΔK curve of A6N01 aluminum alloy base metal and composite welded joint had a cross phenomenon. When ΔK <18.63 MPa · m ~ (1/2), the weld crack growth rate was slower than the base metal, which was considered as safe Reliable service. Fatigue cracks in the composite welding tips were initiated by processing defects, and the source regions of the cracks appeared like river-like streams. Fatigue bands were not observed in the stable crack propagation area; dimples and shards of sharp edges were present in the instantaneous fracture area Quasi-cleavage fracture and ductile fracture of the mixed fracture form.