Stress corrosion cracking resistance of rare earth Gd and ZnO reinforced Mg–Zn nanocomposites developed by novel sonication technique

This research systematically examines the effect of stress corrosion cracking (SCC) on the microstructure modifications of magnesium zinc (Mg–Zn) alloy and Mg–Zn–0.2 Gd–2wt. % ZnO nanocomposites. The examination was conducted in a 3.5% NaCl solution. The performance of Mg–Zn alloy and nanocomposite samples in the SCC environment was assessed using constant load at five distinct stress levels. In Mg–Zn alloy, SCC resistance is determined by a threshold stress value of 27 MPa. However, in Mg–Zn–0.2Gd–2wt. % ZnO nanocomposites, it is 58 MPa. The findings showed that Mg–Zn alloy was more susceptible to SCC than nanocomposites. Adding 0.2Gd and 2% ZnO nanoparticles to Mg–Zn alloy improved the resistance to SCC by refining the grain structure and homogenizing the microstructure. Additionally, the presence of ZnO nanoparticles acted as a barrier during the initial stages of corrosion, further enhancing the resistance to SCC in the nanocomposite sample compared to the pure Mg–Zn alloy. The SEM corrosion analysis reveals that the generated samples exhibit corrosion pits at 20 % YS, a cleavage for Mg–Zn alloy and dimples for nanocomposite were noted between 40 and 60 % YS, and complete stress failure shows completely cleavages facets for Mg–Zn alloy and more dimples for nanocomposites at 80–100 % YS. In response to the weight loss estimate, the corrosion rate of the nanocomposites is improved by 54.5%. Moreover, the stress corrosion map for nanocomposites demonstrates different zones of SCC.