Regularities of Dispersion Hardening of Al-Mg-Si-Cu Alloy during Artificial Aging

Abstract

The effect of solution treatment and aging on the phase composition and physicomechanical properties of an Al-Mg-Si-Cu alloy is investigated. An increase in the solution temperature from 530 to 550°C leads to the hardness increase from 59 ± 1 to 68 ± 2 HV and the electrical conductivity decrease from 38.9 ± 0.1 to 36.0 ± 0.1 % IACS, respectively. The stress–strain curves after solution treatment are characterized by jerky flow or the Portevin–Le Chatelier effect, which is associated with the dissolution of particles at high temperatures and the formation of a supersaturated solid solution in the alloy after solution treatment. Aging at 190°C leads to a nonmonotonic behavior of hardness. The maximum hardness of 143 ± 4 HV is observed after aging for 2 h. The β″, β′, Q′ particles, clusters, and Guinier–Preston zones provide maximum hardness in the alloy. Dispersion hardening leads to an increase in the yield stress and ultimate tensile strength to 340 ± 5 and 390 ± 10 MPa, respectively, at the elongation of about 12.3 ± 1.6%. The high ductility of the alloy (approximately 2% higher than the previously published literature data) may be a result of the absence of needle-like Al₅FeSi particles due to a targeted reduction in the Fe concentration in the alloy.