7xxx aluminum alloys; strengthening mechanisms and heat treatment: a review

Abstract

The intention of authoring this paper was giving the report of reviewing task of the previous researches done on the strengthening mechanisms and heat treatment of 7xxx aluminum alloys. The overall conclusion is that, the most powerful and so the most common strengthening mechanism in 7xxx alloys is the precipitation hardening (T6 heat treatment). On the other hand, stress corrosion is a problem in T6 treated 7xxx alloys, to address which, researchers have turned to special heat treatment called RRA (retrogression and re-aging) which picks the strength from T6, and stress corrosion resistance from T7x heat treatments.

On the effect of interrupted ageing (T6I4) on the mechanical properties of AA6351 and AA7050 alloys

“…Thus, by reducing the ageing temperature in the second stage of the T6I4 heat treatment, most of the GP zones that were nucleated in the first step of the interrupted ageing were consumed in the η' phase formation. This increase in the η' precipitate density is correlated to the improved combination of mechanical properties in AA7050-T6I4 condition, compared to AA7050-T7451 (Buha et al, 2007;Buha et al, 2008;Feizi and Ashjari, 2018). In Figure 1 (d), a coarse intermetallic particle also can be observed along the grain boundary (red arrow) in the AA7050-T7451 condition.…”

Post-processing ageing treatment of friction surfaced Al-16Si alloy: experimental and theoretical studies

“…These mechanisms encompass grain refinement, solid solution strengthening, thermal mismatch, load transfer, and precipitation hardening. 41,42 One of the effective mechanisms for increasing the hardness and strength of the coating is grain refinement. Notably, there is a significant reduction in grain size during the FS process compared to the consumable rod.…”

Effects of Aging Temperature, Time During Transition from Brittle to Ductile on Fracture Behavior of Zinc Coated AA7075

“…They also have seen that AA7075 with T6 temper is exposed to brittle fracture, which exhibit ductile failure. Ashjari and Feizi [27] have expressed that aging temperature and quench-induced precipitation play significant role in improving mechanical strength, which is observed under microscopic studies. Liu et al [28] have studied the effect of solution and aging system on microstructure and mechanical properties of 7000 series aluminum alloy produced by powder metallurgy and noticed decrement in the undissolved phase in the aluminum alloy under increased temperature and time.…”