7A04-T6鋁合金水下攪拌摩擦焊接接頭的組織和性能Microstructure and Mechanical Properties of Underwater Friction Stir Welded 7A04-T6 Aluminum Alloy

在循環(huán)水冷和空氣條件下對7A04-T6鋁合金進行攪拌摩擦焊接(FSW),分析強制冷卻對7A04-T6鋁合金FSW接頭組織性能的影響。結果表明:循環(huán)水冷具有明顯的瞬時快冷作用,顯著抑制再結晶晶粒和析出相的長大,焊核區(qū)的平均晶粒尺寸為0.8μm,析出相尺寸為30~150nm,均小于空氣條件下接頭的晶粒尺寸(2.8μm)及析出相尺寸(80~400nm)。與空氣條件下相比,強制水冷條件明顯改善接頭的力學性能。焊核區(qū)的平均硬度值提高11.9HV,接頭抗拉強度提高43.2MPa,達到母材抗拉強度的87.6%;接頭的應變硬化能力增強,拉伸斷口呈現出微孔聚合型斷裂特征。

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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