铝合金与镁合金直流双脉冲MIG焊接头组织与性能研究

Study of Mechanical Properties and Structure of Al-Mg Dissimilar Welding Joint with DC Double Pulse MIG

以ER4043焊丝为填充金属,对5 mm厚的7020铝合金和AZ31B镁合金的直流双脉冲MIG焊接头进行组织成分和力学性能分析。结果表明,在合适的焊接参数下,焊缝近镁侧熔合区存在柱状晶和200μm左右的铝镁金属间化合物层,其主要成分为β(Al3Mg2)和γ(Al12Mg17)。拉伸试样断裂发生在近镁侧熔合区,呈现脆性断裂的特征,焊缝显微硬度值波动较大,在近镁侧熔合线处达到最大值,铝镁金属间化合物层的存在严重降低了接头力学性能,平均拉伸强度只有16.4 MPa。

5 mm thick 7020 aluminum alloy and AZ31B magnesium alloy are used as base metal to analyze the mechanical proper- ties, structure and composition of the joint welded by DC double pulse MIG with ER4043 welding wire. The results show that, in the proper welding parameters, the columnar crystal and AI-Mg intermetallic compound layer about 200 tim which consists of/3（ AI3 Mg2 ） and y（ Air2 Mgt~ ） exist in the Mg-side fusion zone. The tensile fracture of the specimen occurs near the Mg-side fusion zone, which shows the characteristics of brittle fracture. The microhardness of welding zone greatly changes and the maximum value appears near the Mg-side fusion line. Due to the existence of the AI-Mg intermetallic compound layer, the mechanical properties of the welding joint are reduced greatly. The average tensile strength is only 16.4 MPa.