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Ti40Zr10Cu36Pd14 Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies’ prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%), a hardness of 5.5 GPa and a toughness of 56 MPa.√m. Moreover, the alloy shows a relatively lower Young’s modulus (96 GPa) than the Ti-6Al-4V alloy (110–115 GPa), which is beneficial to limit bone stress shielding. The BMG shows a satisfactory cytocompatibility, a high resistance to sterilization and a good corrosion resistance (corrosion potential of −0.07 V/SCE and corrosion current density of 6.0 nA/cm2), which may ensure its use as a biomaterial. Tests on dental implants reveal a load to failure 1.5-times higher than that of Ti-6Al-4V and a comparable fatigue limit. Moreover, implants could be machined and sandblasted by methods usually conducted for titanium implants, without significant degradation of their amorphous nature. All these properties place this metallic glass among a promising class of materials for mechanically-challenging applications such as dental implants. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) have attracted extensive interest due to their unprecedented structure and mechanical performance. We recently proposed a series of novel corich twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) HEAs with superior tensile properties at room temperature; however, the hot deformation behavior has not been reported. Here, we investigated the dynamic recrystallization behavior and grain refinement of a representative TRIP-HEA, compressed at temperatures of 1123–1273 K with strain rates of 0.1–0.001 s−1. We characterized the impact of the temperature and strain rate on the grain structure evolution. A constitutive equation was constructed to reveal the correlations between the flow stress, strain rate, temperature, and strain. The apparent activation energy was estimated to be ~385.7 kJ/mol. The discontinuous dynamic recrystallization played an important role in the grain refinement, particularly at a relatively higher temperature and a lower strain rate, and the volume fraction and morphology of the recrystallized grains exhibited a strong dependency on the Zener–Hollomon parameter. The study provides guidelines for the grain refinement of HEAs through thermomechanical processing. [ABSTRACT FROM AUTHOR]

New AlxCo50−xCu50−xMnx (x = 2.5, 10, and 15 atomic %, at%) immiscible medium-entropy alloys (IMMEAs) were designed based on the cobalt-copper binary system. Aluminum, a strong B2 phase former, was added to enhance yield strength and ultimate tensile strength, while manganese was added for additional solid solution strengthening. In this work, the microstructural evolution and mechanical properties of the designed Al-Co-Cu-Mn system are examined. The alloys exhibit phase separation into dual face-centered cubic (FCC) phases due to the miscibility gap of the cobalt-copper binary system with the formation of CoAl-rich B2 phases. The hard B2 phases significantly contribute to the strength of the alloys, whereas the dual FCC phases contribute to elongation mitigating brittle fracture. Consequently, analysis of the Al-Co-Cu-Mn B2-strengthened IMMEAs suggest that the new alloy design methodology results in a good combination of strength and ductility. [ABSTRACT FROM AUTHOR]

High-entropy nanomaterials possessing high accessible surface areas have demonstrated outstanding catalytic performance, beating that found for noble metals. In this communication, we report about the synthesis of a new, nanoporous, high-entropy alloy (HEA) possessing open porosity. The nanoporous, high-entropy Ta19.1Mo20.5Nb22.9V30Ni7.5 alloy (at%) was fabricated from a precursor (TaMoNbV)25Ni75 alloy (at%) by liquid metal dealloying using liquid magnesium (Mg). Directly after dealloying, the bicontinuous nanocomposite consisting of a Mg-rich phase and a phase with a bulk-centered cubic (bcc) structure was formed. The Mg-rich phase was removed with a 3M aqueous solution of nitric acid to obtain the open, porous, high-entropy Ta19.1Mo20.5Nb22.9V30Ni7.5 alloy (at%). The ligament size of this nanoporous HEA is about 69 ± 9 nm, indicating the high surface area in this material. [ABSTRACT FROM AUTHOR]

The CoCrNi and precipitate-hardened (CoCrNi)94Ti3Al3 medium entropy alloys (MEAs) have attracted much attention, due to their exceptional mechanical properties, whereas the hot deformation characteristics have not been revealed. In the present study, we investigated the dynamic recrystallization behavior and microstructure evolutions of the two MEAs hot-compressed at single-phase temperatures. The constitutive equation was obtained, and microstructures were observed. Discontinuous dynamic recrystallization acted as a key mechanism of grain refinement at a relatively higher temperature and lower strain rate, which leads to the formation of a homogeneous grain structure. The addition of Ti and Al promoted dynamic recrystallization due to the solid solution hardening effect. The results provide valuable guidelines for microstructure refinement via thermomechanical processing. [ABSTRACT FROM AUTHOR]

Surface functionalization is an effective approach to change the surface properties of a material to achieve a specific goal such as improving the biocompatibility of the material. Here, the surface of the commercial biomedical Ti-6Al-7Nb alloy was functionalized through synthesizing of a porous surface layer by liquid metal dealloying (LMD). During LMD, the Ti-6Al-7Nb alloy is immersed in liquid magnesium (Mg) and both materials react with each other. Particularly, aluminum (Al) is selectively dissolved from the Ti-6Al-7Nb alloy into liquid Mg while titanium (Ti) and niobium (Nb) diffuse along the metal/liquid interface to form a porous structure. We demonstrate that the porous surface layer in the Ti-6Al-7Nb alloy can be successfully tailored by LMD. Furthermore, the concentration of harmful Al in this porous layer is reduced by about 48% (from 5.62 ± 0.11 wt.% to 2.95 ± 0.05 wt.%) after 30 min of dealloying at 1150 K. The properties of the porous layer (e.g., layer thickness) can be tuned by varying the dealloying conditions. In-vitro tests suggest improved bone formation on the functionalized porous surface of the Ti-6Al-7Nb alloy. [ABSTRACT FROM AUTHOR]

In this work, the biomedical applicability and physical properties of magnesium-based metallic glass/polycaprolactone (PCL) composites are explored. The composites were fabricated via mechanical alloying and subsequent coextrusion. The coextrusion process was carried out at a temperature near to the supercooled liquid region of the metallic glass and the viscous region of the polymer. The structures, as well as thermal and mechanical properties of the obtained samples were characterized, and in vivo investigations were undertaken. The composite samples possess acceptable thermal and mechanical properties. Tensile tests indicate the ability of the composites to withstand more than 100% deformation. In vivo studies reveal that the composites are biologically compatible and could be promising for biomedical applications. [ABSTRACT FROM AUTHOR]

Rising demand for bone implants has led to the focus on future alternatives of alloys with better biocompatibility and mechanical strength. Thus, this research is dedicated to the synthesis and investigation of new compositions for low-alloyed Ti-based compounds, which conjoin relatively acceptable mechanical properties and low elastic moduli. In this regard, the structural and mechanical properties of α + β Ti-Fe-Cu-Sn alloys are described in the present paper. The alloys were fabricated by arc-melting and tilt-casting techniques which followed subsequent thermo-mechanical treatment aided by dual-axial forging and rolling procedures. The effect of the concentrations of the alloying elements, and other parameters, such as regimes of rolling and dual-axial forging operation, on the microstructure and mechanical properties were thoroughly investigated. The Ti94Fe1Cu1Sn4 alloy with the most promising mechanical properties was subjected to thermo-mechanical treatment. After a single rolling procedure at 750 °C, the alloy exhibited tensile strength and tensile plasticity of 1300 MPa and 6%, respectively, with an elastic modulus of 70 GPa. Such good tensile mechanical properties are explained by the optimal volume fraction balance between α and β phases and the texture alignment obtained, providing superior alternatives in comparison to pure α- titanium alloys. [ABSTRACT FROM AUTHOR]

The present work was aimed to demonstrate the possibility of forming Fe66Cr10Nb5B19 metallic glass coatings by detonation spraying and analyze the coating formation process. A partially amorphous Fe66Cr10Nb5B19 powder with particles ranging from 45 µm to 74 µm in diameter was used to deposit coatings on stainless steel substrates. The deposition process was studied for different explosive charges (fractions of the barrel volume filled with an explosive mixture (C2H2 + 1.1O2)). As the explosive charge was increased from 35% to 55%, the content of the crystalline phase in the coatings, as determined from the X-ray diffraction patterns, decreased. Coatings formed at explosive charges of 55–70% contained as little as 1 wt.% of the crystalline phase. In these coatings, nanocrystals in a metallic glass matrix were only rarely found; their presence was confined to some inter-splat boundaries. The particle velocities and temperatures at the exit of the barrel were calculated using a previously developed model. The particle temperatures increased as the explosive charge was increased from 35% to 70%; the particle velocities passed through maxima. The coatings acquire an amorphous structure as the molten particles rapidly solidify on the substrate; cooling rates of the splats were estimated. The Fe66Cr10Nb5B19 metallic glass coatings obtained at explosive changes of 55–60% showed low porosity (0.5–2.5%), high hardness (715–1025 HV), and high bonding strength to the substrate (150 MPa). [ABSTRACT FROM AUTHOR]

Titanium carbide (TiC), is the most thermodynamically stable compound in the Ti–C–Cu system, which makes it a suitable reinforcement phase for copper matrix composites. In this work, the interaction of a Ti–Cu alloy with different forms of carbon was investigated to trace the structural evolution leading to the formation of in-situ TiC–Cu composite structures. The reaction mixtures were prepared from Ti25Cu75 alloy ribbons and carbon black or nanodiamonds to test the possibilities of obtaining fine particles of TiC using ball milling and Spark Plasma Sintering (SPS). It was found that the behavior of the reaction mixtures during ball milling depends on the nature of the carbon source. Model experiments were conducted to observe the outcomes of the diffusion processes at the alloy/carbon interface. It was found that titanium atoms diffuse to the alloy/graphite interface and react with carbon forming a titanium carbide layer, but carbon does not diffuse into the alloy. The diffusion experiments as well as the synthesis by ball milling and SPS indicated that the distribution of TiC particles in the composite structures obtained via reactive solid-state processing of Ti25Cu75+C follows the distribution of carbon particles in the reaction mixtures. This justifies the use of carbon sources that have fine particles to prepare the reaction mixtures as well as efficient dispersion of the carbon component in the alloy–carbon mixture when the goal is to synthesize fine particles of TiC in the copper matrix. [ABSTRACT FROM AUTHOR]

Even though the Mg-based bulk metallic glasses (BMGs) have shown superior anti-corrosion properties compared with their crystalline counterparts, the brittleness of them limits the widespread application of these materials. In the present study, we have firstly introduced porous NiTi shape memory alloy particles into an Mg-Zn-Ca BMG by the direct adding method. This composite showed both improved compressive strength and corrosion resistance in Hank's solutions than its monolithic glassy counterpart. The NiTi dispersoids among the matrix were likely to hinder the main shear band propagation, and also acted as the corrosion barriers. Furthermore, the porous nature of present added particle could further increase the interface areas, which should enhance the reinforcing effects compared with solid ones. This low-cost, high-anticorrosive composite was a good candidate as an engineering material. [ABSTRACT FROM AUTHOR]

Ti40Zr10Cu36Pd14 Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies’ prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%), a hardness of 5.5 GPa and a toughness of 56 MPa.√m. Moreover, the alloy shows a relatively lower Young’s modulus (96 GPa) than the Ti-6Al-4V alloy (110–115 GPa), which is beneficial to limit bone stress shielding. The BMG shows a satisfactory cytocompatibility, a high resistance to sterilization and a good corrosion resistance (corrosion potential of −0.07 V/SCE and corrosion current density of 6.0 nA/cm2), which may ensure its use as a biomaterial. Tests on dental implants reveal a load to failure 1.5-times higher than that of Ti-6Al-4V and a comparable fatigue limit. Moreover, implants could be machined and sandblasted by methods usually conducted for titanium implants, without significant degradation of their amorphous nature. All these properties place this metallic glass among a promising class of materials for mechanically-challenging applications such as dental implants. [ABSTRACT FROM AUTHOR]

Titanium carbide (TiC), is the most thermodynamically stable compound in the Ti-C-Cu system, which makes it a suitable reinforcement phase for copper matrix composites. In this work, the interaction of a Ti-Cu alloy with different forms of carbon was investigated to trace the structural evolution leading to the formation of in-situ TiC-Cu composite structures. The reaction mixtures were prepared from Ti 25 Cu 75 alloy ribbons and carbon black or nanodiamonds to test the possibilities of obtaining fine particles of TiC using ball milling and Spark Plasma Sintering (SPS). It was found that the behavior of the reaction mixtures during ball milling depends on the nature of the carbon source. Model experiments were conducted to observe the outcomes of the diffusion processes at the alloy/carbon interface. It was found that titanium atoms diffuse to the alloy/graphite interface and react with carbon forming a titanium carbide layer, but carbon does not diffuse into the alloy. The diffusion experiments as well as the synthesis by ball milling and SPS indicated that the distribution of TiC particles in the composite structures obtained via reactive solid-state processing of Ti 25 Cu 75 +C follows the distribution of carbon particles in the reaction mixtures. This justifies the use of carbon sources that have fine particles to prepare the reaction mixtures as well as efficient dispersion of the carbon component in the alloy-carbon mixture when the goal is to synthesize fine particles of TiC in the copper matrix., Competing Interests: The authors declare no conflict of interest.

Ti 40 Zr 10 Cu 36 Pd 14 Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies' prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%), a hardness of 5.5 GPa and a toughness of 56 MPa.√m. Moreover, the alloy shows a relatively lower Young's modulus (96 GPa) than the Ti-6Al-4V alloy (110-115 GPa), which is beneficial to limit bone stress shielding. The BMG shows a satisfactory cytocompatibility, a high resistance to sterilization and a good corrosion resistance (corrosion potential of -0.07 V/SCE and corrosion current density of 6.0 nA/cm²), which may ensure its use as a biomaterial. Tests on dental implants reveal a load to failure 1.5-times higher than that of Ti-6Al-4V and a comparable fatigue limit. Moreover, implants could be machined and sandblasted by methods usually conducted for titanium implants, without significant degradation of their amorphous nature. All these properties place this metallic glass among a promising class of materials for mechanically-challenging applications such as dental implants., Competing Interests: The authors declare no conflict of interest.