铝合金与镁合金直流双脉冲MIG焊接头组织与性能研究

摘要

5 mm thick 7020 aluminum alloy and AZ31B magnesium alloy are used as base metal to analyze the mechanical properties,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 Al-Mg intermetallic compound layer about 200 μm which consists of β(Al3 Mg2)and γ(Al12Mg17) 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 Al-Mg intermetallic compound layer,the mechanical properties of the welding joint are reduced greatly.The average tensile strength is only 16.4 MPa.%以ER4043焊丝为填充金属,对5mm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200 μ.m左右的铝镁金属间化合物层,其主要成分为β(Al3 Mg2)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.