The Influence of Heat Treatment on the Mechanical Properties and Corrosion Resistance of the Ultrafine-Grained AA7075 Obtained by Hydrostatic Extrusion

Abstract

In this paper, the corrosion resistance and mechanical properties of the 7075 aluminum alloy are studied. The alloy was deformed by hydrostatic extrusion and then aged both naturally and artificially. Results are compared with those of coarse-grained material subjected to T6 heat treatment. The aim of the research is to find the optimal correlation between the mechanical properties and the corrosion resistance of the alloy. To this end, static tensile tests with subsequent fractography, open circuit potential, and potentiodynamic polarization tests in 0.05 M NaCl were conducted. Obtained results show that a combination of precipitate hardening and a deformed microstructure leads to increased mechanical strength with high anisotropy due to the presence of fibrous grains. Plastic deformation increases susceptibility to corrosion due to the increased number of grain boundaries, which act as paths along that corrosion propagates. However, further artificial aging incurs a positive effect on corrosion resistance due to changes in the chemical composition of the matrix as a result of the precipitation process.

Impact of Marine Atmospheric Corrosion on the Microstructure and Tensile Properties of 7075 High-Strength Aluminum Alloy

“…Some studies to date explored the corrosion behavior of 7075 alloy [ 12 , 13 , 14 , 15 , 16 ]. Marta Orłowska et al studied the impact of heat treatment on the mechanical properties and corrosion resistance of ultra-fine-grained 7075 alloy and found that plastic deformation increased susceptibility to corrosion due to an increase in grain boundaries [ 12 ].…”

“…Some studies to date explored the corrosion behavior of 7075 alloy [ 12 , 13 , 14 , 15 , 16 ]. Marta Orłowska et al studied the impact of heat treatment on the mechanical properties and corrosion resistance of ultra-fine-grained 7075 alloy and found that plastic deformation increased susceptibility to corrosion due to an increase in grain boundaries [ 12 ]. Liwei Wang et al studied the corrosion evolution of high-strength aluminum alloys in a solution and a thin electrolyte layer containing Cl − and found that large corrosion cavities with limited underlying microcracks were formed [ 14 ].…”

Increasing the Mechanical Strength and Corrosion Resistance of Aluminum Alloy 7075 via Hydrostatic Extrusion and Aging

“…Therefore, this paper adopts a more comprehensive approach, and attempts to correlate appropriate heat treatment of 7xxx AAs that have undergone HE with the development of high mechanical strength and high resistance to corrosion in an aggressive environment. This work is a continuation of our previous work, where the influence of heat treatment on the single-stepped hydrostatically extruded AA7075 was investigated [20].…”

Low‐Cycle‐Fatigue Performance of Stress‐Aged EN AW‐7075 Alloy

“…[17] It is well known that GP zones and η´precipitates can considerably improve the strength of EN AW-7075 alloy, while coarse η precipitates detrimentally affect the hardening of this alloy. [22,23] Additionally, during the growth of coarse η precipitates, the flux of solute atoms toward formed precipitates occurs, resulting in the depletion of alloying elements in the vicinity of coarse precipitates and eventually the formation of precipitate-free zones (PFZs) in the microstructure. [12,14] It was reported that these PFZs can adversely affect the mechanical properties of EN AW-7075 alloy.…”