Abstract: An effective method of measuring continuous cooling transformation(CCT) curve is studied. Corresponding to different cooling rate range, the different measurement methods are employed. The phase-transformation temperatures at slow cooling rate are determined by differential thermal analysis(DTA). The phase-transformation temperatures at medium cooling rate are obtained by measuring a ratio of resistance change against temperature. The phase-transformation temperatures at high cooling rate are measured with thermal mechanical simulator and X-ray diffractometer. Mechanical property combined with microstructure of the samples at various cooling rates is studied and the CCT curve of the alloy is constructed. When the cooling rate increases, phase- transformation temperature drops and the quantity of the secondary phase decreases. The solid solution strengthening is the leading strengthening mechanism during the quench and the hardness increases with the increase of the cooling rate.

Key words: Al-Cu-Li alloy; CCT curve; phase transformation; strengthening mechanism