Magnesium alloys are increasingly prioritized for lightweight engineering applications; however, their industrial utility is often limited by microstructural stability and corrosion susceptibility. In the present study, the microstructure, corrosion behavior, and joinability of AZ31 magnesium alloys modified by varying concentrations of rare earth elements, specifically neodymium (Nd) and lanthanum (La), were comprehensively investigated. Two specific compositions, AZ31-0.5Nd-0.2La and AZ31-0.5Nd-0.5La, were synthesized via induction melting and subsequently processed through hot rolling to produce sheets with a precise thickness of 1.5 mm. To evaluate their structural integration potential, these processed alloys were successfully joined with interstitial-free (IF) steel through a mechanical clinching process. Detailed microstructural characterization was performed utilizing scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The analysis revealed that secondary intermetallic phases, primarily enriched with Al-Mn-Nd and Al-La-Nd, were predominantly distributed along the grain boundaries in both alloy variants. Potentiodynamic polarization tests were executed in a 3.5% NaCl solution across three distinct cross-sections (S1, S2, and S3) to ensure experimental consistency. Quantitative data indicated that the AZ31-0.5Nd-0.5La alloy exhibited superior corrosion resistance compared to the AZ31-0.5Nd-0.2La alloy, as evidenced by significantly lower icorr and mpy values. Long-term immersion corrosion tests further confirmed these findings, showing that while metal loss generally increased with duration, the AZ31-0.5Nd-0.5La alloy achieved the lowest metal loss (0.79 g) after 16 hours. Ultimately, the results demonstrate that an increased lanthanum content is highly favorable for enhancing the microstructural stability and corrosion resistance of AZ31 magnesium alloys.
Mhawesh et al. (Wed,) studied this question.