终时效对 7475 铝合金微观组织和力学性能的影响

Effect of final aging on microstructure and mechanical properties of 7475 aluminum alloy during two-stage aging treatment was studied by means of transmission electron microscopy and universal material testing machine. The results show that when the first aging process is 120 ℃ × 5 h and final aging process is 160 ℃ × 14 h, the amount of precipitated phases in the alloy matrix is large, the precipitates are fine and dispersed, the precipitation free zone at the grain boundary is relatively narrow, and the precipitated phases at the grain boundary are discontinuously distributed. At this time, the tensile strength, yield strength and elongation of the alloy are the best, which are 509 MPa, 463 MPa and 12. 4%, respectively. Compared with the untreated alloy, the tensile strength, yield strength and elongation increase by 4. 5%, 9. 2% and 11. 7%, respectively. When the final aging temperature is 160 ℃, with the increase of the final aging time, the strength of the alloy first increases and then decreases, but the change is not significant. When the final aging temperature is greater than or equal to 165 ℃, the strength of the alloy decreases significantly with the increase of the final aging time, which is due to the significant broadening of the width of the precipitate free zone at the grain boundary and the significant coarsening of the matrix precipitated phase.