Evaluation of the Effect of Dual-Stage Aging and RRA on the Hardening and Corrosion Resistance of AW7075 Alloy

Abstract

The corrosion resistance of the AW7075 alloy after RRA treatment was evaluated. The corrosion rate in the NSS test was assessed and the electrochemical parameters were determined. The results were compared with the results obtained for the alloy subjected to conventional aging (T6) and dual-stage aging (DA). In order to determine the state of alloy hardening, the tests were carried out simultaneously with the material hardness measurements and microscopic examinations. The hardness of the AW7075 alloy increased in the following order: DA < T6 < RRA. The tests revealed that the achieved increase in strengthening was correlated with the preservation of high resistance to general corrosion of the alloy after RRA treatment. After the corrosion tests, SEM microscopic observations were also carried out to determine the corrosion features. The corrosion rate can be arranged in the following order: RRA < T6 ≈ DA. At the same time, the alloy after RRA was characterized by the lowest value of the corrosion potential and the open circuit. The corrosion potential value can be presented in increasing order: RRA < T6 ≈ DA. The corrosion behavior of the aluminum alloy after dual-stage aging was similar to that of T6. However, it was accompanied by a decline in hardening.

Effect of Dual-stage Ageing and RRA Treatment on the Three-body Abrasive Wear of the AW7075 Alloy

“…The effect of heat treatment of aluminium alloys on their strength is already known. Its influence on the resistance to structural corrosion is also well understood [12] to [16]. Retrogression and re-ageing treatment improve the resistance to stress corrosion cracking (SCC) [6], while maintaining high strength, until the MPs become coarse [6].…”

Metallurgical aspects of the corrosion resistance of 7000 series aluminum alloys – a review

“…The presence of discontinuous precipitates GBPs also favors a high resistance to the initiation of fatigue cracks and a high impact strength [6,14,15]. At the same time, we observe resistance to general corrosion to state T6 as well as hardness close to that state, which ensures good tribological properties [34,61].…”

“…The presence of intermetallic phases in the microstructure of aluminum alloys creates a wide spectrum of possibilities for forming their properties aluminum. In the case of the alloys from the 7000 series, both the conventional methods of precipitation hardening and the RRA technology (retrogression and re-aging) are applied [25,34,[51][52][53][54][55][56][57][58]. Figure 1 presents a scheme of the course of aging in reference to the hardness of an aluminum alloy subjected to conventional aging.…”