时效处理对7050铝合金组织与性能的影响

Effect of Aging Treatment on Microstructure and Properties of 7050 Aluminium Alloy

对7050铝合金进行硬度测试、腐蚀性能测试和透射电子显微分析(TEM),研究了单级时效处理对合金组织与性能的影响。实验结果表明:7050铝合金具有较强的时效硬化效应。单级时效温度由120℃升高到160℃时,合金时效硬化速度显著加快,合金进入峰时效状态所需时间显著缩短,但合金的峰值点的硬度降低。时效处理后合金晶内析出了大量的尺寸细小的η’相,弥散分布在基体中。合金晶界处析出了粗大的平衡相,成分为MgZn2,PFZ出现。随着时效温度的升高,合金晶间析出相连续且粗大,PFZ宽化,合金的抗晶间腐蚀性能持续下降。对于剥落腐蚀来说,合金的腐蚀程度不仅与晶界结构有关,还与晶界数量有关,温度上升,合金晶粒尺寸迅速增大,晶界数目显著减少,二者相互作用最终导致了合金的抗剥落腐蚀性能的提高。

The 7050 aluminium alloys are widely used in the aviation and aerospace for their higher strength,fracture toughness property and anti-fatigue performance. The effects of single-stage aging on alloy tissue and performance were studied by the hardness test,corrosion test and transmissive electron microscopic analysis(TEM) of 7050 aluminum alloys. The experimental results show that the 7050 aluminum alloys have a strong aging hardening effect. When the single-stage aging temperature rises from 120℃ to 160℃,the speed of alloy aging hardening accelerates significantly,and the time required for alloys to enter the peak aging state is significantly shortened,but the hardness of the peak point of the alloys reduces. After aging treatment,the alloy precipitates abundant of fine η’ phase dispersing in the matrix. A coarse equilibrium phase is precipitated at the grain boundary of the alloy with MgZn2 as the component and PFZ appears. With increasing aging temperature,the precipitation phase on the grain boundary is continuous and coarse,PFZ is widened and the intergranular corrosion resistance of the alloy continues to decrease. For exfoliation corrosion,the degree of alloy corrosion is related not only to the structure of the grain boundary but also to the number of it. As the temperature rises,the grain size of the alloy increases rapidly,and the number of the grain boundary reduces significantly,the interaction of which results in the improvement of the alloy’s anti-corrosion property.