CAJ | 학술논문

The effects of the retrogression temperature and time of retrogression and re-aging heat treatment(RRA) on the hardness and electrical conductivity of Al-6.1Zn-2.6Mg-1.6Cu aluminum alloy were studied. Samples were pre-aged at 120℃ for 24h as the first-stage treatment. Then, retrogression was performed at a temperature range of 170～250℃ for times of between 1min and 180min, followed by re-aging at 120℃ for 24h. Hardness (H) and electrical conductivity (EC) measurements were used to characterize the samples after RRA treatment. Analysis of the results shows: (1)The re-aging treatment at 120℃ for 24 h increases both H and EC of the retrogressed alloy in the RRA process;(2) RRA with retrogression at higher than 200℃ result in EC higher than that of peak-aged, but H lower; The change of H and EC with respect to retrogression temperature (T) and time (t) can be seen as functions of H (t) = H0+A1e(-t/s) ,EC(t) =A(1-e(-k·(t-Xc)));(3) RRA treatments with retrogression at 190℃ for 4～30min result in H and EC which are both higher than those of the peak-aged temper, and retrogression at 190℃for 30min is the industrial application that yields H of 190 HV and EC of 33.5%IACS.