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Magnesium-based composites are promising materials that can achieve higher strength, modulus, stiffness, and wear resistance by using metals, ceramics, and nanoscale carbon-based materials as reinforcements. In the last few decades, high-performance magnesium-based composites with excellent interfacial bonding and uniformly distributed reinforcements have been successfully synthesized using different techniques. The yield strength, Young’s modulus, and elongation of SiC nanoparticle-reinforced Mg composites reached ∼710 MPa, ∼86 GPa, and ∼50%, respectively, which are the highest reported values for Mg-based composites. The present work summarizes the commonly used reinforcements of magnesium composites, particularly nano-reinforcements. The fabrication processes, mechanical properties, reinforcement dispersion, strengthening mechanisms, and interface optimization of these composites are introduced, and the factors affecting these properties are explained. Finally, the scope of future research in this field is discussed.

The effects of Al and Sc on mechanical properties of FeCoNi multi-element alloys (MEAs) were investigated by compressive tests. The microstructures of FeCoNi MEAs with different contents of Al and Sc were characterized and the strengthening mechanisms were discussed. The results show that FeCoNi MEA with a low content of Al has a face-centered cubic (FCC) structure. The yield strength increases linearly with the increase of Al content, which is largely caused by solid solution hardening. Further addition of Sc can promote the formation of a new phase in (FeCoNi)1−xAlx MEAs. A minor addition of Sc can significantly increase the yield strengths of (FeCoNi)1−xAlx MEAs with a low Al content and improve the compressive plasticity of (FeCoNi)1−xAlx MEAs with a high Al content.

Split Hopkinson Tension Bar (SHTB) experiments were conducted to explore the dynamic mechanical behavior and deformation mechanism of powder metallurgical (PM) Ti−47Al−2Nb−2Cr−0.2W (at.%) intermetallics with near lamellar (NL) and duplex (DP) microstructures. Results show that, under dynamic loading, the high temperature strength of the PM TiAl intermetallics is higher than that under quasi-static loading, and the ductile to brittle transition temperature (DBTT) increases with the increase of strain rate. Formation of twinning and stacking faults is the main deformation mechanism during dynamic loading. The work hardening rates of the PM TiAl intermetallics are nearly insensitive to strain rate and temperature at high strain rates (800−l600 s −1 ) and high temperatures (650−850 °C). Zerilli−Armstrong model is successfully used to describe the dynamic flowing behavior of the PM TiAl intermetallics. In general, the PM TiAl intermetallics are found to have promising impact properties, suitable for high-temperature and high-impact applications.

Isothermal oxidation behaviors of Ti-45Al-2Fe-2Mo-1Cr intermetallics with different oxygen contents were studied under the condition of 950 °C, 100 h in air, and the oxidation kinetic parameters were also evaluated. The results show that the oxidation resistance of the TiAl intermetallics is negatively related to the oxygen content, and both the mass gain and thickness of oxide scale increase with the oxygen content. The sub-surface microstructure of the oxide scales varies with the oxygen content. Z phase is observed in the sub-surface area of the low-oxygen-content alloy, while the τ2(Al2FeTi) phase is found in the medium-oxygen-content and the high-oxygen-content alloys. The deterioration of oxidation resistance is due to the enhanced internal oxidation with the increase of oxygen content. It is possible to improve the oxidation resistance by controlling the oxygen content.

To improve the high-temperature deformability of TiAl intermetallics, a TiAl–Nb intermetallic matrix composite was prepared by powder metallurgy to try to introduce the deformable β phase. The microstructure and deformation behavior of the TiAl–Nb intermetallic matrix composite under quasi-static and dynamic conditions were systematically investigated. It is found that the microstructure of the composite is composed of a near-gamma TiAl matrix and Nb-rich regions. In the Nb-rich regions a coexistence of βo, ωo and γ phases was identified where ωo and γ phases were supposed to directly precipitate in the βo matrix. The ultimate tensile strength of the composite exhibits different temperature-dependent behaviors under quasi-static and dynamic loading conditions. It increases with temperatures up to 650 °C and then declines with temperature under quasi-static loading, while it does not decrease from 650 to 850 °C under the dynamic loading. In the deformed microstructures, the Nb-rich regions at all conditions are still composed of βo, ωo and γ phases, indicating that the solvus temperature of the ωo phase could be above 850 °C. Additionally, the TiAl matrix appears to not significantly contribute to the plastic deformation of the composite, where the propensity of dislocations and mechanical twins do not significantly change when varying loading conditions. However, the γ particles formed in Nb-rich regions contain substantial mechanical twins and dislocations under both quasi-static and dynamic loading conditions. Thus, the γ particles directly transformed from the βo phase exhibit better deformability than the γ phase in the matrix. This could be probably explained by a decreased stacking fault energy for the newly formed γ phase due to a decrease in Al fraction and a significant increase in Nb fraction. Meanwhile, twin intersections occurred in the γ particles, and the induced stress concentration in the intersection regions was relieved by lattice distortion and detwinning processes. This twin intersection behavior could be beneficial for improving the composite strength without sacrificing much ductility.

Implant-associated infections still represent major challenge to successful implantation. Titanium and its alloys are attractive implant materials for orthopedic applications. However, they lack of effective antibacterial activities against bacterial infection. Heterogeneous metallic materials can induce galvanic corrosion in physiological solution, and this phenomenon can also induce antibacterial action. In this work, we fabricated Ti-Mg metal-metal composites (MMCs) with different contents of Mg-Zn alloy by spark plasma sintering (SPS). We quantitatively evidenced that microscale electric fields formed between Ti and Mg area in MMCs by using atomic force microscopy (AFM). The formation of microscale electric fields effectively inhibited the adhesion and growth of Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) on Ti-Mg MMCs. Moreover, the antibacterial behavior could be controlled by tuning microscale electric fields, revealing the effect of the electron transfer in the antibacterial process. The electron transfer between the Mg-rich area and titanium matrix could induce local alkaline environment leading to bacterial death. Moreover, the presence of microscale electric fields could induce burst generation of reactive oxygen species (ROS) in bacteria, which also caused bacterial death by inducing intracellular oxidation, membrane potential variation, and the release of cellular contents. The findings can provide new insights for understanding the antibacterial action of Ti-Mg MMCs that exhibit great potential as orthopedic implants. The results also offer new concepts for designing metal-metal composite implants with non-antibiotic solution for combatting infections by controlling microscale electric fields.

The 2-amino benzene dicarboxylic acid (H2BDC-NH2) modified TiO2 was prepared via hydrothermal method. The surface areas of unmodified and modified TiO2 were 23.206 and 231.908 m2/g, and the according light absorption range changed from 400 nm to 540 nm. The modified TiO2 exhibited 3 times higher visible-light photocatalytic degradation efficiency for four types of azo dyes than unmodified TiO2 and commercial P25. The ligand H2BDC of modified TiO2 generated photoelectrons and holes under visible light irradiation, producing OH• and O2•− active sites for the dye degradation. Moreover, the modified TiO2 showed excellent stability, which suggests the as-prepared composite to be a promising photocatalyst.

In the present study, pre-deformation was applied to a metastable β titanium alloy (Ti-36Nb-2Ta-3Zr-0.35O) with the hope of improving its overall mechanical properties. The microstructural evolution and mechanical properties of the as-rolled alloys with different thickness reductions (from 4% to 35%) were characterized and analyzed. The results show that increasing the amount of pre-deformation can increase the strength (yield strength and tensile strength) of the Ti-36Nb-2Ta-3Zr-0.35O alloy without (4%–15% pre-deformation) or with only minor (23%–35% pre-deformation) sacrifice of ductility. Due to the increase of pre-deformation reduction, the β phase stability increases, leading to the twinning activities and the evolution of twinning system, which contribute to the strain hardening and the good ductility of the alloy pre-deformed by 9% and 15%.

Developing bioactive glass nanoparticles (BGNs) comprising biologically active ions is a promising strategy to enhance therapeutic performance. Given the pro-osteogenic activity of rubidium (Rb), a new type of Rb-containing BGNs was developed in this work. Here, a modified Stӧber method was employed to synthesize monodispersed spherical BGNs (particle size ~ 100 nm) with different contents of Rb incorporation (nominal 1, 3 and 5 at.%). The results showed that Rb incorporation did not significantly affect the size, shape and amorphous characteristic of BGNs. The real Rb contents (maximum 0.62 at.%) in BGNs were much lower than the designed ones. Compared with Rb-free BGNs, Rb-BGNs exhibited enhanced hydroxyapatite-forming ability in simulated body fluid. The results suggest that Rb-BGNs are promising to be used as bioactive fillers for bone regeneration applications.

In this work, Ti—Mg metal-metal composites (MMCs) were successfully fabricated by spark plasma sintering (SPS). In vitro, the proliferation and differentiation of SaOS-2 cells in response to Ti—Mg metal-metal composites (MMCs) were investigated. In vivo, a rat model with femur condyle defect was employed, and Ti—Mg MMCs implants were embedded into the femur condyles. Results showed that Ti—Mg MMCs exhibited enhanced cytocompatibility to SaOS-2 cells than pure Ti. The micro-computed tomography (Micro-CT) results showed that the volume of bone trabecula was significantly more abundant around Ti—Mg implants than around Ti implants, indicating that more active new-bone formed around Ti—Mg MMCs implants. Hematoxylin-eosin (H&E) staining analysis revealed significantly greater osteointegration around Ti—Mg implants than that around Ti implants., Graphical abstract Image 1, Highlights • Bioactive Ti—Mg metal-metal composites (MMCs) were successfully fabricated by spark plasma sintering. • The proliferation and ALP activity of SaOS-2 cells were promoted by Ti—Mg MMCs extraction medium. • In vivo results showed that Ti—Mg MMCs exhibited enhanced osseointegration compared to pure Ti.

In this work, Ti and Mg alloys were made into composites by using spark plasma sintering, in order to combine the high stiffness of Ti and biodegradability of Mg alloys. The effect of the content of Mg–3Zn alloy on the degradability was studied by using electrochemical corrosion, immersion in simulated body fluid and incubation of Saos-2 cells. The results show that Ti–Mg metal-metal composites (MMCs) exhibit low Young's modulus (31–48 GPa) and good yield strength (616.5–642.8 MPa). The modulus and strength both decrease with the content of Mg–3Zn alloy increasing. The electrochemical corrosion rates of Ti–Mg MMCs were much lower than that of monolithic Mg–3Zn alloys. After an immersion for 21 days, Ti matrix remained integrity and Mg phase dissolved in the solution, inducing the formation of apatite layer on the MMCs. The precipitation of apatite increased with the content of Mg–3Zn alloy increasing. In vitro study indicated that Ti–10Mg and Ti–20 Mg MMCs possessed good biocompatibility to Saos-2 cells, while the biocompatibility of Ti–30 Mg MMCs decreased slightly. In summary, Ti–Mg MMCs are promising implant materials with adjustable degradation rates and improved biocompatibility for orthopedic applications.