Effects of Aging Treatment on Nano-Sized Precipitates and Properties of Spray Formed Al-Zn-Mg-Cu Alloy

摘要

The effects of aging treatment on nano-sized precipitates and properties of spray formed Al-Zn-Mg-Cu alloy were investigated by tensile test and plane strain fracture toughness (K-IC) test. The microstructures of alloys were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed that T6 samples showed the best strength but the worst fracture toughness. The main fracture mechanism was the intergranular fracture. After over-aged treatment (T76), the strength was decreased and the fracture toughness was increased, and the alloy exhibited intergranular fracture. With the increase of the aging time (T74), the alloy exhibited the best fracture toughness, while the lowest strength. It exhibited a mix of transgranular and intergranular fracture. The size of precipitated-free zones (PFZs) in T74 was about 61.1 nm, which played an important role to obtain high fracture toughness.