Sreenivas Raguraman

With an increasing demand for biodegradable structural materials, magnesium (Mg) alloys stand out as promising candidates. Here, we investigate the corrosion-induced mechanical degradation of fine wires made from WE43 and ZX10 Mg alloys, evaluating their suitability for biomedical applications such as scaffolds, stents, and sutures. Both alloys exhibit distinct microstructural features that influence their corrosion and mechanical behavior. WE43 wires, characterized by neodymium-rich precipitates and elongated grains, showed significant axial pitting corrosion and a rapid decline in mechanical properties attributed to micro-galvanic corrosion and potential hydrogen embrittlement. In contrast, ZX10 wires, featuring coarser and heterogeneously distributed Mg2Ca precipitates, demonstrated extensive localized pitting but retained higher ductility and toughness over extended exposure. Micro-CT analyses reveal that precipitate size, distribution, and volume fraction critically influence corrosion morphology and mechanical degradation. The findings emphasize the importance of tailoring alloy microstructures to enhance corrosion resistance and mechanical performance. While WE43’s higher corrosion rates and more rapid property degradation limit its potential in applications with fine dimensions, ZX10’s lower corrosion rate and higher mechanical resilience make it a more viable candidate. Future research should prioritize developing chemically homogeneous precipitates in ZX10 that are small and uniformly distributed.

Biodegradable magnesium (Mg) alloys are gaining attention for biomedical implants due to their favorable mechanical properties and safe degradation within the human body. However, the rapid corrosion of Mg remains a challenge, necessitating a deeper understanding of its behavior in physiological environments. This study evaluates the in vitro corrosion performance of a lean Mg-Zn-Ca alloy processed via equal channel angular pressing to refine the grain size and enhance the mechanical properties. Corrosion behavior was assessed in Hank’s balanced salt solution (HBSS), Earle’s balanced salt solution (EBSS) buffered with 5% CO2, and Dulbecco’s modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) buffered with 5% CO2. Significant differences in corrosion rates were observed across media, with HBSS exhibiting the lowest rates and EBSS the highest. DMEM with 10% FBS and corrosion conditions that most closely resemble physiological environments produced intermediate corrosion rates. The effect of CO2 buffering in HBSS was also evaluated, demonstrating enhanced pH control below 7.5, which simulates physiological pH. Additionally, increasing the volume of HBSS, both with and without CO2 buffering, led to reduced corrosion rates and greater pH stabilization. These findings shed light on how testing conditions can impact corrosion rates and pH stability.

Magnesium alloys are increasingly recognized as promising materials for biomedical implants due to their low density, biocompatibility, and favorable mechanical properties. However, achieving a balance between mechanical strength and bio-corrosion resistance remains a critical challenge. This study evaluates the effects of three thermomechanical processing techniques — extrusion (EXT), Equal Channel Angular Pressing (ECAP), and ECAP followed by low-temperature annealing at 150°C for 10 hours (ECAP-A) — on the microstructure, mechanical properties, and bio-corrosion behavior of the ZX10 magnesium alloy. EXT resulted in a coarse, elongated grain structure, increased volume fraction of Mg2Ca particles, and moderate mechanical and corrosion performance. ECAP lowered the volume fraction of Mg2Ca particles and significantly refined the grain structure, and increased dislocation density, improving hardness by 80%, yield strength, and ductility. However, the corrosion rate doubled due to the high dislocation density. Post-ECAP annealing (ECAP-A) mitigated this limitation, reducing the corrosion rate to 1.50 mm/year while maintaining a high yield strength (>200 MPa). This improvement was driven by a uniform distribution of the Ca2Mg6Zn3 phase, a further reduction of the Mg2Ca phase, and decreased dislocation density. These findings demonstrate that ECAP, followed by annealing, optimally balances mechanical performance and bio-corrosion resistance, making the ZX10 magnesium alloy a promising candidate for biodegradable implant applications

Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability, biocompatibility, and impressive mechanical characteristics. However, their rapid in-vivo degradation presents challenges, notably in upholding mechanical integrity over time. This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy, ZX10. Utilizing rapid, cost-efficient characterization methods like X-ray diffraction and optical microscopy, we swiftly examine microstructural changes post-thermal treatment. Employing Pearson correlation coefficient analysis, we unveil the relationship between microstructural properties and critical targets (properties): hardness and corrosion resistance. Additionally, leveraging the least absolute shrinkage and selection operator (LASSO), we pinpoint the dominant microstructural factors among closely correlated variables. Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca2Mg6Zn3 phase in corrosion behavior. This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases. This thorough investigation furnishes valuable insights into the intricate interplay of processing, structure, and properties in magnesium alloys, thereby advancing the development of superior biodegradable implant materials.

Magnesium alloys offer immense potential as intelligent alternatives to traditional implant materials due to their inherent degradability, biocompatibility, and exceptional mechanical properties. However, their rapid deterioration hinders their practical applications, compromising their mechanical integrity. This study addresses this challenge by investigating the effects of thermo-mechanical processing, including extrusion, cECAP, rolling, and annealing, on the high-strength, dilute ZX10 Mg alloy. By subjecting the alloy to over thirty processing conditions, we identify an optimal combination of high-strength and low-corrosion rates. Simple characterization techniques like XRD, optical microscopy, and SEM were employed to rapidly evaluate the microstructural changes post-processing. The findings identify that grain boundary and strain hardening play pivotal roles in enhancing hardness, while factors such as texture, dislocation density, and precipitates impact corrosion significantly. This comprehensive investigation provides valuable insights into processing-structure–property relationships for Mg alloys, paving the way for developing superior biodegradable implant materials.