Investigation of the Susceptibility of the WE54 Magnesium-Based Alloy to Stress Corrosion Cracking

Abstract

This article presents an assessment of the susceptibility of the WE54 magnesium-based alloy to stress corrosion cracking in an 0.1 M Na2SO4 environment. In this work, the basis criterion for assessing the alloy’s behavior under complex mechanical and corrosive loads is the deterioration in its mechanical properties (elongation—ε, %, reduction in area—Z, %, tensile strength—Rm, MPa) along with a fractographic analysis of fracture surfaces. The WE54 magnesium-based alloy was subjected to the slow strain rate test (SSRT) under mechanical loads in corrosive environment (0.1 M Na2SO4 solution). The test was carried out in four variants: (a) SSRT in air, (b) cathodic hydrogen charging for 24 h at a current density of 50 mA/cm2 followed by SSRT in air, (c) SSRT in a corrosive environment under open-circuit potential conditions, and (d) SSRT in a corrosive environment under cathodic polarization at a current density of 50 mA/cm2. In each variant, the content of hydrogen in the alloy was determined. It was demonstrated that under SCC conditions, in the presence of hydrogen, the plastic properties of WE54 decreased significantly, whereas the alloy’s strength properties changed to a smaller degree. The change in the mechanical properties under SCC conditions in a corrosive environment was accompanied by a change in the fracture surface morphology and by the presence of numerous cracks, both on fracture surfaces and in the alloy’s microstructure.