The Effect of Anodic Dissolution on Stress Relaxation in Metals Using Magnesium Alloys and Steel as Examples: A Review

The effect of surface dissolution in corrosive solutions on the stress relaxation (SR) in metals is of great interest for structural and mechanical engineering. However, limited data on corrosion stress relaxation (CSR) pose serious challenges for engineering applications. This review analyzes the SR in magnesium alloys and various steels in air, as well as the CSR in Mg alloys and Fe-6.5%Si steel compared to air. In air, Mg alloys show a relatively high resistance to stress relaxation, but in aqueous solutions containing NaCl and Na₂B₄O₇, the alloys exhibit a noticeable decrease in stress compared to that in air, especially with an increase in temperature from 25 to 70 °C. In CSR tests on silicon steel, it was found that as the pH of the corrosion solution decreased, the stress losses increased significantly. A greater difference in the SR behavior of alloys in air and in aggressive solutions is shown by alloys with structural heterogeneity of the AZ91D and AS21 Mg alloys, which is confirmed by metallography and relaxation time spectra. As a result of chemomechanical effect (CME), anodic dissolution of the stressed metal accelerates its plasticization due to the diffusion of vacancies, causing the destruction of pileups and the emergence of an additional avalanche flow of dislocations, as well as multiple slip in the polycrystalline material.