| dc.description.abstract |
Mg alloys have recently attracted interest as biodegradable implant materials due to their biocompatibility and suitable mechanical properties. However, their rapid degradation rate re- quires further tailoring through alloying additions and thermomechanical processing. This work investigates the effects of Gd (0,1,2 wt.%) alloying and post-casting rolling and extrusion on the microstructure, mechanical performance, and corrosion of Mg-2Zn-0.5Y (wt.%) alloys. XRD and microscopy analysis revealed that the cast alloys consist of α-Mg and Mg3Zn6Y (I-phase), while Gd additions promote the formation of W Phase (Mg3Zn3Gd2) secondary phases. The presence of the W phase induces significant grain refinement down to an average grain size of 204.67 µm from 265.56 µm in Gd-free alloys. Furthermore, severe plastic deformation and dynamic recrystallization during rolling and extrusion lead to a more refined grain structure compared to the cast condition. Hardness increases with Gd content and with the rolling and extrusion process, resulting from precipitation strengthening and additional Hall-Petch strengthening enabled by extensive grain refinement. However, the corrosion rate increases in Gd-containing alloys due to an increase in surface roughness, as determined by AFM studies and galvanic coupling between W-phase particles and the Mg matrix. Weight loss testing shows that the corrosion rate increases in Gd added alloys relative to the Gd-free alloy. In contrast, rolling and extrusion disrupt galvanic effects and improve surface protection, reducing corrosion rate compared to as-cast alloys on average across compositions. These insights on synergies among composition, microstructure, and thermomechanical processing advance knowledge for designing biodegradable Mg implants with tailored degradation. |
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