DETERMINATION AND APPLICATION OF CCT DIAGRAM FOR 6082 ALUMINUM ALLOY
LI Hongying 1, ZHAO Yankuo 1, TANG Yi 2, WANG Xiaofeng 1
1. School of Materials Science and Engineering, Central South University, Changsha 410083
2. Institute of Pumping, SANY Heavy Industry Co., Ltd, Changsha, 410083
Cite this article:
LI Hongying ZHAO Yankuo TANG Yi WANG Xiaofeng. DETERMINATION AND APPLICATION OF CCT DIAGRAM FOR 6082 ALUMINUM ALLOY. Acta Metall Sin, 2010, 46(10): 1237-1243.
Abstract Electrical resistance–temperature curves of 6082 aluminum alloy at various cooling rates during continuous cooling was obtained by in–situ resistance measurement. Phase transformation start and finish temperatures were ascertained by the slope change of resistance–temperature curves. Continuous cooling transformation (CCT) diagram for 6082 aluminum alloy was plotted. Microstructure evolution during cooling was examined by TEM observation to verify the validity of the CCT diagram. Applications of the CCT diagram were studied in this work. The results show that the CCT diagram obtained by in situ resistance measurement is credible. Resistance–temperature curves corresponding to different cooling rates depart from straight line to different directions. The phase transformation start and finish temperature decreases with the increase of cooling rates when the cooling rate is slow, but as the cooling rate increases to a certain rate the phase transformation start temperature increases suddenly and then decreases continously. Phase transformations mainly take place between 220 and 400 ℃. Critical cooling rate for preventing phase transformation is between 16—34 ℃/s. For plates 20 mm in thickness is proper to quench by 60 ℃ water. A step–quench process can be established by the tested CCT diagram to decrease quenching stress utmost and inhibit equilirium phase precipitation at the same time.
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