Investigating the effects of deformation-induced densification on the constitutive behavior and corrosion resistance of Al–Zn–Mg powder metallurgy alloy during hot deformation

Abstract

The electrochemical behavior is most strongly influenced by deformation, which may either accelerate or decelerate failure during service. Therefore, in the present study, the Al–5.6Zn–2Mg alloy fabricated by powder metallurgy was subjected to hot deformation at various temperatures (300–500 °C) and strain rates (0.5–0.005 s−1) on a hydraulic press, and then, the effect of deformation-induced densification on corrosion behavior was studied using electrochemical corrosion tests. Flow stress is mathematically modeled using the strain-compensated Arrhenius model. The model developed was reliable to predict, with an average absolute relative error (AARE) of 3.16% and an R2 value of 0.98. The potentiodynamic polarization results showed that as the degree of porosity in a sintered sample is reduced, there was a decrease in the corrosion current density and an increase in the pitting potential. Al–5.6Zn–2Mg corrosion resistance significantly improved with deformation temperature, whereas strain rates decrease it, due to a decrease in pore content. Icorr of 2.4982 µA/cm2 and Epit of 0.876 V have been found for the highly deformed preforms under 500 °C and 0.005 s−1 strain rate condition. EIS results showed a high contact resistance of 2659 Ohm·cm2 and high hardness value of 113.12 Hv for the preform deformed under 500 °C and 0.005 s−1 strain rate. The reduction in porosity, decrease in active surface area after the deformation process, densification behavior, and hardness are all related to the electrochemical behavior. Pitting corrosion was observed in deformed preforms as a corrosion mechanism; the dynamic recovery feature is observed from the flow behavior.