Study On The Heat Treatment Of2297Aluminum Alloy

:In this paper,2297aluminum alloy was taken for the subject of the research. The hardness and tensile strength were tested. And the characterization of the microstructure was investigated by optical microscope (OM), scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) and transmission electron microscopy (TEM). The effect of homogenization process, solution treatment, aging process on the microstructure and mechanical property of experimental alloy were discussed. Results are as follows:1) The main microstructure in as-cast microstructure is Cu-rich and equaxed a-Al grain and serious dendritic segregation exists in the as-cast experimental alloy. Segreation of the main elements Cu, Mg, and Mn are observed at the grain boundary. The overburnt temperature of the as-cast experimental alloy is550℃. With increased temperature or prolonged holding time at the temperature below overburning, the eutectic phases in the grain boundary gradually dissolve into the matrix. The dendrite segregation is improved, and the grain boundaries become sparse and thin. The proper single homogenizationp processing is530℃/24h, the proper two stage homogenization is480℃/16h+530℃/20h.2) When the solution temperature is between505℃to535℃, the residual gradually dissolve into the matrix and the size of recrystallized grains increase during solution treatment with increased temperature. When the temperature is increasing to550℃, the number of secondary phase does not chang obviously, and the size of grain is particularly larger. When the solution temperature is535℃and the holding time is between0.5h to1.5h, the number of secondary phase decrease gradually with the prolonged solution time. When the solution time is more than1.5h, the number of secondary phase has changed little and the grain size increases significantly. Considering microstructure evolution and mechanical property of2297alloy, the suitable solution processing is535℃/1.5h.3) During ageing treatment, the number of T1phase increases gradually and average the sieze of T1phases rises gradually. Compared to the T1phases of T6-aged alloy, the size of T1phases in T8-aged alloy is smaller and more diffuse and the strength is higher than that of T6-aged alloy. The proper T6aging processing is175℃/24h. The suitable T8aging processing is5%pre-deformation+160℃/32h.