非等温蠕变时效对Al-Zn-Mg-Cu合金力学性能和耐腐蚀性能的影响

Effect of Nonisothermal Creep Aging on Mechanical Properties and Corrosion Resistance of Al-Zn-Mg-Cu Alloy

摘要:

研究了非等温蠕变时效处理中升温速率和峰值温度对Al-Zn-Mg-Cu合金回弹性能、力学性能和耐腐蚀性能的影响。通过透射电镜分析了合金的析出行为和时效强化机理。结果表明：随着加热速率的降低和峰值温度的升高，合金的回弹率降低；晶内析出相的尺寸增大，而体积分数先增大后减小；晶界析出相逐渐变得不连续，无析出区扩大。经非等温蠕变时效（20 ℃/h，180 ℃）处理后的合金主要析出相为致密的η'相，晶界析出相不连续，无析出区的宽度约为44.2 nm。非等温蠕变时效（20 ℃/h，180 ℃）处理的合金力学性能和耐腐蚀性能均优于常见的等温蠕变时效（120 ℃，24 h）处理的合金，并且时效时间缩短了67%。

关键词:Al-Zn-Mg-Cu合金;非等温蠕变时效;析出相;力学性能;耐腐蚀性能

Abstract:

The effects of the heating rate and peak temperature on the springback, mechanical properties, and corrosion resistance of Al-Zn-Mg-Cu alloy were investigated. The precipitation behavior and aging strengthening mechanism of the alloy were analyzed by transmission electron microscope. Results show that with decreasing the heating rate and increasing the peak temperature, the springback of the alloy is decreased; the size of intragranular precipitates is increased; the volume fraction of intragranular precipitates is firstly increased and then decreased; the grain boundary precipitates become discontinuous and the precipitate-free zone is expanded. After nonisothermal creep aging (NICA) treatment (20 °C/h, 180 °C), the main precipitates of alloy are compact η' phase, the grain boundary precipitates are discontinuous, and the free zone width is approximately 44.2 nm. The mechanical properties and corrosion resistance of the alloy treated by NICA (20 °C/h, 180 °C) are better than those of the alloy treated by common isothermal creep aging (120 °C, 24 h), and the aging time is shortened by 67%.

Key words:Al-Zn-Mg-Cu alloy;nonisothermal creep aging;precipitation phase;mechanical properties;corrosion resistance