To develop novel biodegradable magnesium alloys with suitable corrosion resistance and mechanical properties for orthopedic applications, this study investigated the microstructure, mechanical properties, corrosion behavior and wear resistance of as-cast and near-solidus heat-treated Mg-3Zn-0.3Mn alloys with and without Gd/Nd additions (RE-free, 1Gd, 1Gd1Nd). Rare earth addition refined the grains and transformed the secondary phase from Mg7Zn3 to the W-phase (Mg3RE2Zn3). The as-cast 1Gd1Nd alloy showed the finest grains, highest hardness (51.3 HB), best tensile strength (189.38 MPa), lowest corrosion rate (2.80 mm/y) and lowest wear rate (0.614 × 10−3 mm3/(N·m)). Near-solidus heat treatment slightly decreased hardness (1–3%) but significantly reduced corrosion rate (e.g., RE-free alloy from 3.61 to 2.78 mm/y) and wear rate. The heat-treated 1Gd1Nd alloy gave the best overall performance: corrosion rate 2.68 mm/y, tensile strength 213.71 MPa and elongation 12.96%. Gd promoted grain refinement and film stability, while Nd stabilized the W-phase, showing a clear combined addition benefit. Notably, the heat-treated RE-free alloy performed similarly to the as-cast 1Gd1Nd alloy, indicating that heat treatment can partially mimic rare earth addition. This work provides a baseline for precursor materials before further processing (e.g., extrusion) toward biodegradable implant applications.
Yang et al. (Thu,) studied this question.