Microstructural evolution and mechanical properties of an Al-10Zn-3Mg-2.5Cu alloy processed by stress-aging coupled artificial aging

XW Ren and WZ Liang and Y Zhang and ZM Zhang and Q Wang and X Zhao and SB Bai and M Meng, MATERIALS & DESIGN, 260, 114984 (2025).

DOI: 10.1016/j.matdes.2025.114984

Herein, we investigate the effect of stress-aging on the precipitate characteristics, grain structure, dislocation evolution, and mechanical properties of an Al-10Zn-3Mg-2.5Cu (wt.%) alloy. Stress aging was performed at 120 degrees C for 24 h under applied stresses of 135-450 MPa, which considerably enhanced the tensile strength to 700 MPa and resulted in dislocation multiplication as the dominant strengthening mechanism. However, the alloy ductility was constrained to 3.7 %-5.4 %. The stress-aged specimens with 270 MPa and 450 MPa were subjected to artificial aging (140 degrees C-160 degrees C). This considerably enhanced the strength-ductility synergy, endowing a tensile strength of 700 MPa along with elongations of 9.1 % and 6.5 %. epsilon-CuZn4 precipitation was facilitated by synergistic high-alloying and dislocation effects. This rare phase effectively suppressed the coarsening of eta-phase, thereby preserving the intrinsic strength, while its superior capability to trap and accumulate dislocations significantly enhanced the ductility. Thus, high-stress aging and thermal treatment offered transformative phasetransformation pathways, distinct from conventional eta-phase evolution, making it ideal for fabricating highstrength Al-Zn-Mg-Cu alloys.

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