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As most Mg alloy products are now produced by a casting process, the development of high strength cast Mg alloys can promote their further applications and has already become one of the hot research areas of Mg alloys. The present paper reviews the strengthening mechanisms, tensile properties and modification results of commercial high strength cast Mg alloys; as well as the development of Mg-Gd, Mg-Nd and Mg-Sn based alloys. It concludes that precipitation strengthening is the most important strengthening mechanism in high strength cast Mg alloys, which contributes more than 60% of yield strength in solution & peak-aged (T6) cast Mg alloys. For the yield strength, the alloys follow the sequence of Mg-Gd(Y)-Ag > Mg-Gd(Y)-Zn > Mg-Gd-Y/Sm/Nd > Mg-Y-Nd (WE series) > ZK61 > Mg-Nd > AZ91 > Mg-Sn. Mg-Gd(Y)-Ag based alloys are the strongest cast Mg alloys at present, followed by Mg-Gd(Y)-Zn based alloys. The high yield strengths of Mg-Gd(Y)-Ag and Mg-Gd(Y)-Zn cast alloys are due to the co-precipitation of basal and prismatic meta-stable phases.

Abstract: In present work, the NdH2 precipitates in Mg–2.5%Nd (wt.%) alloy were identified by various microstructural analyzing techniques including OM, XRD, TEM with EELS, SEM with EDS, etc. It was revealed that the as-cast alloy contained α-Mg solid solution and eutectic phase Mg12Nd, while there were NdH2 particles at or near the grain boundaries in 540°C/6h solution-treated state. As widely acknowledged, they worsen its mechanical property, especially, the cracking and fracture behaviors. Synchronously, the formation of hydride NdH2 is proved to be favored and practicable based on thermodynamics theory. [Copyright &y& Elsevier]

Osteoporotic fracture is one of the most serious complications of osteoporosis. Most fracture sites have bone defects, and restoring the balance between local osteogenesis and bone destruction is difficult during the repair of osteoporotic bone defects. In this study, we successfully fabricated three-dimensional (3D)-printed biodegradable magnesium alloy (Mg-Nd-Zn-Zr) scaffolds and prepared a zoledronic acid-loaded ceramic composite coating on the surface of the scaffolds. The osteogenic effect of Mg and the osteoclast inhibition effect of zoledronic acid were combined to promote osteoporotic bone defect repair. In vitro degradation and drug release experiments showed that the coating significantly reduced the degradation rate of 3D-printed Mg alloy scaffolds and achieved a slow release of loaded drugs. The degradation products of drug-loaded coating scaffolds can promote osteogenic differentiation of bone marrow mesenchymal stem cells as well as inhibit the formation of osteoclasts and the bone resorption by regulating the expression of related genes. Compared with the uncoated scaffolds, the drug-coated scaffolds degraded at a slower rate, and more new bone grew into these scaffolds. The healing rate and quality of the osteoporotic bone defects significantly improved in the drug-coated scaffold group. This study provides a new method for theoretical research and clinical treatment using functional materials for repairing osteoporotic bone defects., Competing Interests: The authors declare no conflict of interest.., (Copyright:© 2023, Ran Z, Wang Y, Li J, et al.)

Magnesium (Mg) alloys that have both antibacterial and osteogenic properties are suitable candidates for orthopedic implants. However, the fabrication of ideal Mg implants suitable for bone repair remains challenging because it requires implants with interconnected pore structures and personalized geometric shapes. In this study, we fabricated a porous 3D-printed Mg-Nd-Zn-Zr (denoted as JDBM) implant with suitable mechanical properties using selective laser melting technology. The 3D-printed JDBM implant exhibited cytocompatibility in MC3T3-E1 and RAW267.4 cells and excellent osteoinductivity in vitro . Furthermore, the implant demonstrated excellent antibacterial ratios of 90.0% and 92.1% for methicillin-resistant S. aureus (MRSA) and Escherichia coli , respectively. The 3D-printed JDBM implant prevented MRSA-induced implant-related infection in a rabbit model and showed good in vivo biocompatibility based on the results of histological evaluation, blood tests, and Mg 2+ deposition detection. In addition, enhanced inflammatory response and TNF-α secretion were observed at the bone-implant interface of the 3D-printed JDBM implants during the early implantation stage. The high Mg 2+ environment produced by the degradation of 3D-printed JDBM implants could promote M1 phenotype of macrophages (Tnf, iNOS, Ccl3, Ccl4, Ccl5, Cxcl10, and Cxcl2), and enhance the phagocytic ability of macrophages. The enhanced immunoregulatory effect generated by relatively fast Mg 2+ release and implant degradation during the early implantation stage is a potential antibacterial mechanism of Mg-based implant. Our findings indicate that 3D-printed porous JDBM implants, having both antibacterial property and osteoinductivity, hold potential for future orthopedic applications., Competing Interests: All authors have read and approved the manuscript and have no conflicts of interest to disclose., (© 2021 The Authors.)