热暴露对7475-T761铝合金微观组织和力学性能的影响

The effects of the thermal exposure on microstructure and mechanical properties of 7475-T761 Al alloy were studied by universal material testing machine, transmission electron microscopy (TEM) and scanning electron microscope (SEM). The results show that the strength of the alloy increases slightly when the alloy is exposed at 100 ℃. When the alloy is exposed at 125 ℃, the strength of the alloy decreases slightly and the mechanical properties remain stable for a long time. When the thermal exposure temperature is higher than 150 ℃, the alloy strength reduces sharply and the elongation increases rapidly with the prolongation of time. Coarsening of matrix precipitates (MPt), coarsening of grain boundary precipitates (GBP), and widening of precipitate free zones (PFZ) should be responsible for the strength decline and elongation rise of 7475-T761 Al alloy during thermal exposure. With increasing the temperature or prolonging the time, the fracture mechanism of the alloy gradually transforms from mixed fracture including intergranular fracture and dimple fracture to transgranular dimple fracture. The main factor that affect the fracture behavior of the alloy is the intensity difference between matrix and grain boundary.