Microstructure and corrosion behavior of Mg-Nd-Fe-B alloys with varying magnet content

Abstract

A systematic study was conducted to evaluate the corrosion behavior of a novel magnesium alloy, Mg–Nd–Fe–B, incorporating varying percentages of neodymium magnet scrap. Immersion tests were performed in a sodium chloride (NaCl) solution at room temperature to assess corrosion resistance. The objective was to enhance the corrosion resistance of a new family of lightweight ternary alloys within the Mg–Nd–Fe–B system. X-ray diffraction (XRD) was employed to identify the crystalline phases, while scanning electron microscopy (SEM) was used to examine the microstructure of samples before and after corrosion. The alloys primarily consisted of ?-Mg and Nd?Fe??B phases. Post-corrosion analysis revealed the presence of corrosion products rich in rare earth elements, with the dominant phase being a solid solution of magnesium and neodymium. Corrosion testing showed the formation of a black, neodymium-based surface layer, which acted as a protective barrier. The corrosion rate decreased significantly with increasing magnet scrap content, with the optimal composition (approximately 30 wt%) achieving an 87.3% reduction in corrosion rate compared to alloys with lower magnet content. Additionally, Vickers hardness testing demonstrated a notable improvement in hardness, further supporting the alloy’s suitability for engineering applications. These findings highlight the beneficial role of rare earth elements, particularly neodymium, in improving both the corrosion resistance and mechanical properties of magnesium-based alloys.