TTP curve of aluminum alloy 7050
摘要
The time—temperature—property (TTP) curve of aluminum alloy 7050 was determined by an interrupted quench method. The results show that the quench sensitive temperature range of TTP curve of alloy is 240?420℃ with the nose temperature of 330 ℃. Microstructure observation indicates that the supersaturated solid solution decomposites and particles precipitate during quench process, the precipitation rate is the highest at about 330 ℃. A number of coarse equilibrium η particles precipitate at grain boundaries and in the grains during isothermal-holding at 330 ℃. Prolonging holding time leads to more and coarser η particles in the matrix, which results in loss of solutes and decrease of subsequent aging hardening effect, and more spaced η particles at the grain boundary that widen precipitation free zone. In the quench sensitive sector, primary precipitating reasons of η particles are severe phase transformation driving force and high diffusion rate of solute atoms. According the results, speeding up the cooling rate in the quench sensitive sector to reduce the precipitation of equilibrium phase is meaningful, and at higher temperature, decreasing the cooling rate is helpful to relieve the effect of thermal load.