Two-step Aging Treatment for a New Al-Zn-Mg-Cu Type of High Strength-Tough Aluminum Alloy Profile

A suitable two-step aging treatment for a new Al-Zn-Mg-Cu type of high strength-tough aluminum alloy profile was obtained by aging treatment and tensile test methods. The results show that the precipitates in the alloy mainly consisted of η′ and η phase after the two-step aging treatment, and the amounts of the η phases increased and the dimensions of the precipitates enlarged with the prolonging of the 2nd step aging time. The hardness of the alloy first increased then decreased with the increase of the aging time, and the strength decreased while the elongation increased with the increase of the 2nd step aging time. The two-step aging process of aging at 120 ℃ for 4 h followed by a re-aging at 165 ℃ for 6 h was determined as a suitable one. After treated by the suitable aging treatment, the tensile strength, yield strength, elongation and electrical conductivity of the alloy were 566 MPa, 540 MPa, 10.9% and 40.8%IACS respectively, and were better than those of 7050-T74 aluminum alloy.