7A04-T6铝合金水下搅拌摩擦焊接接头的组织和性能Microstructure and Mechanical Properties of Underwater Friction Stir Welded 7A04-T6 Aluminum Alloy

在循环水冷和空气条件下对7A04-T6铝合金进行搅拌摩擦焊接(FSW),分析强制冷却对7A04-T6铝合金FSW接头组织性能的影响。结果表明:循环水冷具有明显的瞬时快冷作用,显著抑制再结晶晶粒和析出相的长大,焊核区的平均晶粒尺寸为0.8μm,析出相尺寸为30~150nm,均小于空气条件下接头的晶粒尺寸(2.8μm)及析出相尺寸(80~400nm)。与空气条件下相比,强制水冷条件明显改善接头的力学性能。焊核区的平均硬度值提高11.9HV,接头抗拉强度提高43.2MPa,达到母材抗拉强度的87.6%;接头的应变硬化能力增强,拉伸断口呈现出微孔聚合型断裂特征。

7A04-T6 aluminum alloy was welded by friction stir in the air and cooling water media respectively, and the effects of the forced cooling on the microstructure and mechanical properties of 7A04-T6 FSW joint were analyzed. The results show that the circulating cooling water has obvious instantaneous cooling effect, which significantly restrains the growth of grain recrystallization and precipitated phase. Average grain size and precipitated phase are 0.8μm and 30-150nm respectively in nugget zone under the condition of cooling water, both of which are smaller than the average grain size of 2.8μm and precipitated phase of 80-400nm under the condition of air cooling. Compared to the condition of air cooling, forced cooling significantly improves the mechanical properties of FSW joint. Average microhardness in nugget zone increases by 11.9HV, and tensile strength increases by 43.2MPa, which is 87.6% of that in base metal. Meanwhile, strain hardening capacity of FSW joint in cooling water also enhances, and the tensile fracture presents the characteristic of microporous polymeric fracture.

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