预时效对7475铝合金微观组织和力学性能的影响

The effects of pre-aging on the microstructure and mechanical properties of 7475 aluminum alloy during two-stage aging treatment were studied by transmission electron microscopy (TEM) and universal material testing machine. The results show that the optimal pre-aging process is 120 ℃/5 h, the mechanical properties are the best after final aging treatment of 165 ℃/18 h, and the tensile strength, yield strength and elongation are 489 MPa, 441 MPa and 12.3 %, respectively. The matrix precipitates(MPt)are numerous and the sizes are slight and uniformly dispersed. The grain boundary precipitates (GBP) are discontinuous, and precipitation free zone(PFZ) in grain boundaries is narrower. When the pre-aging temperature is 115 ℃, with the extension of pre-aging time, the strength monotonously increases. When the pre-aging temperature is higher than 120 ℃, with the extension of pre-aging time, the strength increases at first and then decreases.