1 State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083; 2 School of Mechanical and Electrical Engineering, Central South University, Changsha 410083
Abstract: The time-temperature-transformation (TTT) curve and time-temperature-property (TTP) curve of 7085 aluminum alloy were determined by an interrupted quench technique. The microstructure transformation during isothermal treatment was stu-died by the transmission electron microscopy (TEM). Our experiment confirmed an electro-conductivity increasing trend and a hardness decreasing trend of the 7085 alloy during isothermal treatment, both of which change faster in the moderate temperature range. The nose temperatures of the TTT and TTP curves are about 320 ℃ and the high quench sensitive temperature ranges from 250 ℃ to 370 ℃. Microstructure observation indicated that the supersaturated solid solution decomposes and equilibrium η precipitates, and the precipitation rate reaches the highest value at about 320 ℃. η particles precipitate, agglomerate and grow as the isothermal treatment processes, which results in loss of solutes and decrease of the property. In the quench sensitive range, η particles’ rapid preci-pitation and growth can be attributed to high diffusion rate of solute atoms and large driving force of phase transformation.
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2018, Vol. 32 
