Achieving high performance by optimized heat treatment in a spray formed Al–Zn–Mg–Cu alloy

Abstract

High strength Al–Zn–Mg–Cu alloys are widely used for structure components in engineering applications, such as aerospace, transportation, owing to a superior combination of high strength to density ratio and excellent mechanical properties. In present work, the effect of solution treatment and aging treatment on precipitates and mechanical property is investigated in a spray formed (SFed) Al–Zn–Mg–Cu alloy. The SFed Al alloy after optimized solution treatment shows fine grains and high fraction of substructures, which increase the kinetics for precipitation and refine precipitates. It is found that the aging temperature mainly affects the size and phase type of matrix precipitates, size of grain boundary precipitates and width of precipitate free zone. It confirms that both the strength and ductility are controlled by precipitates, which are strongly dependent on aging temperature. Specifically, the sample aged at 120 °C for 16 h (120 °C@16h) behaves highest yield strength (661 MPa) caused by the fine precipitates, while the sample aged with 100 °C@24h behaves highest ultimate tensile strength (745 MPa), uniform elongation (9.1 %) and total elongation (12.5 %). In addition, the strain hardening behavior of SFed Al–Zn–Mg–Cu alloy is discussed by Kocks-Mecking model and an empirical rule.