新型Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr合金单级时效行为研究

One-Step Ageing Behavior of a Novel Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr Alloy

摘要:

通过力学性能和电导率测试以及显微组织的TEM分析，研究新型Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr合金的单级时效行为特征。结果表明：当时效温度由100 ℃升高至160 ℃时，合金时效硬化响应速度明显加快，合金进入过时效状态所需的时间缩短，合金的电导率明显提高。与通常的120 ℃，24 h峰时效态相比，合金经140 ℃, 14 h时效处理后，抗拉强度、屈服强度、断后伸长率和电导率分别达到585 MPa, 560 MPa, 16.1 %和22.6 MS/m，其抗拉强度仅降低1%，屈服强度却提高4%，电导率更是提高11%，作为单级时效制度具有较明显的优势。合金峰时效状态下的主要强化相是细小弥散分布的η’相和GP区。随着时效温度的升高，晶内和晶界的析出相粗化，140 ℃时效时出现明显的晶间无析出带

Abstract:

The one-step ageing behavior of a novel Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy was studied by measuring the mechanical properties and electrical conductivity, and the evolution of microstructure during the aging was investigated by using TEM. The results show that the aging response rate was greatly accelerated with elevating the aging temperature from 100 ℃ to 160 ℃, and the time achieved to over-aged stage was remarkably decreased, while the electrical conductivity of the alloy became higher. After aging for 14 h at 140 °C, the UTS, TYS, Elongation and Electrical conductivity values were achieved to 585 MPa, 560 MPa, 16.1% and 22.6 MS/m, respectively; Comparing with the T6 temper condition performed at 120 ℃ for 24 h, the UTS decreased only by 1%, whereas the TYS and the electrical conductivity obviously increased by 4% and 11%, respectively. The major strengthening precipitates of the peak-aged alloy were the η’ phase and GP zones. The precipitates in both the matrix and the grain boundary became coarser with rising aging temperature. There were obvious PFZs along the grain boundary when the aging treatment was performed at 140 ℃