Optimization of annealing treatment and comprehensive properties of Cu-containing Ti6Al4V-xCu alloys

The Ti6Al4V-Cu alloy was reported to show good antibacterial properties, which was promising to reduce the hazard of the bacterial infection problem. For the purpose of preparing Ti6Al4V-Cu alloy with satisfied comprehensive properties, it’s important to study the heat treatment and the appropriate Cu content of the alloy. In this study, high Cu content Ti6Al4V-xCu (x = 4.5, 6, 7.5 wt%) alloys were prepared, and firstly the annealing heat treatments were optimized in the α+β+Ti₂Cu triple phase region to obtain satisfied tensile mechanical properties. Then the effect of Cu content on the tribological property, corrosion resistance, antibacterial activity and cytotoxicity of the Ti6Al4V-xCu alloys were systematically studied to obtain the appropriate Cu content. The results showed that the optimal annealing temperatures for Ti6Al4V-xCu (x = 4.5, 6, 7.5 wt%) alloys were 720, 740 and 760 °C, respectively, which was resulted from the proper volume fractions of α, β and Ti₂Cu phases in the microstructure. The additions of 4.5 wt% and 6 wt% Cu into the medical Ti6Al4V alloy could enhance the wear resistance and corrosion resistance of the alloy, but the addition of 7.5 wt% Cu showed an opposite effect. With the increase of the Cu content, the antibacterial property was enhanced due to the increased volume fraction of Ti₂Cu phase in the microstructure, but when the Cu content was increased to 7.5 wt%, cytotoxicity was presented. A medium Cu content of 6 wt%, with annealing temperature of 740 °C make the alloy possesses the best comprehensive properties of tensile properties, wear resistance, corrosion resistance, antibacterial property and biocompatibility, which is promising for future medical applications.     

Optimization of mechanical property,antibacterial property and corrosion resistance of Ti-Cu alloy for dental implant

Ti-Cu alloys with different Cu contents (3, 5 and 7 wt%) were fabricated and studied as novel antibacterial biomaterials for dental application. The Ti-Cu alloys were annealing treated at different temperatures (740 °C, 830 °C and 910 °C) in order to obtain three typical microstructures, α-Ti + Ti₂Cu, α-Ti + transformed β-Ti, and transformed β-Ti. Mechanical, antibacterial and biocorrosion properties of Ti-Cu alloys with different microstructures were well analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile test, electrochemical test and antibacterial test. The results indicated that the Ti-Cu alloys with microstructure of α-Ti + Ti₂Cu showed the best ductility compared with other Ti-Cu alloys with microstructures of α-Ti + transformed β-Ti and complete transformed β-Ti, and meanwhile, increase of the Cu content significantly contributed to the decreased ductility due to the increasing amount of Ti₂Cu, which brought both solid solution strengthening and precipitation strengthening. Finally, the Ti-5Cu alloy with microstructure of α-Ti + Ti₂Cu exhibited excellent ductility, antibacterial property and corrosion resistance, providing a great potential in clinical application for dental implants.     

钛表面铜离子注入对细菌和细胞行为的影响

医用钛及其合金被广泛用作骨组织替换材料,但缺乏抗菌性,易导致细菌感染。铜具有良好的抗菌性能,将其引入到钛表面,可改善医用钛的抗菌性能;然而铜含量过高对细胞具有毒性。因此,需要调节铜的含量,实现铜的抗菌性能和细胞相容性之间的平衡。本研究采用等离子体浸没离子注入技术对医用钛进行表面改性,获得表面含铜量不同的样品,并研究改性钛表面对细菌和细胞行为的影响。结果表明,钛表面含铜量较低的样品能够促进大鼠骨髓间充质干细胞(rBMSCs)和人脐静脉内皮细胞(HUVECs)的增殖,但对大肠杆菌和金黄色葡萄球菌没有抑制能力;随着离子注入时间的延长,钛表面含铜量较高的样品抗菌能力显著提高,同时也未产生明显细胞毒性。因此,通过控制钛表面的铜含量,可以获得兼具良好抗菌性能和生物相容性的钛植入材料。     

Effects of scandium addition on the in vitro degradation behavior of biodegradable Mg–1.5Zn–0.6Zr alloy

Heretofore, recognitions of the systematic effects of scandium addition on corrosion behavior of biodegradable magnesium alloys are not yet clear. In the present study, a series of Mg–1.5Zn–0.6Zr–xSc (ZK21–xSc, x?=?0, 0.2, 0.5, 1.0 wt.%) alloys were casted and investigated with respect to the immersion and electrochemical degradation behavior. The hydrogen evolution, pH monitoring, ion release and mass loss results demonstrated that ZK21–0.2Sc alloy exhibited the lowest corrosion rate. The surface morphology analyses displayed that an obvious uniform corrosion occurred in ZK21–xSc alloys with Sc content below 0.5, while localized corrosion occurred in ZK21–1.0Sc alloy. Corrosion potentials of ZK21–xSc alloys shifted toward more positive with the increasing Sc content. But ZK21–0.2Sc alloy exhibited the lowest corrosion current density and the largest corrosion film resistance. Compared with other developed Mg alloys, the ZK21–0.2Sc alloy demonstrated a superior degradation behavior.     

Nd-induced honeycomb structure of intermetallic phase enhances the corrosion resistance of Mg alloys for bone implants

Mg-5.6Zn-0.5Zr alloy (ZK60) tends to degrade too rapid for orthopedic application, in spite of its natural degradation, suitable strength and good biocompatibility. In this study, Nd was alloyed with ZK60 via laser melting method to enhance its corrosion resistance. The microstructure features, mechanical properties and corrosion behaviors of ZK60-xNd (x?=?0, 1.8, 3.6, 5.4 wt.%) were investigated. Results showed that laser melted ZK60-xNd were composed of fine ɑ-Mg grains and intermetallic phases along grain boundaries. And the precipitated intermetallic phases experienced successive changes: divorced island-like MgZn phase?→?honeycomb-like T phase?→?coarsened and agglomerated W phase with Nd increasing. It was worth noting that ZK60-3.6Nd with honeycomb-like T phase exhibited an optimal corrosion behavior with a corrosion rate of 1.56?mm?year^?1. The improved corrosion behavior was ascribed to: (I) dense surface film caused by the formation of Nd₂O₃ hindered the invasion of immersion solution; (II) the three-dimensional honeycomb structure of intermetallic phases formed a tight barrier to restrain the propagation of corrosion. Moreover, ZK60-3.6Nd exhibited good biocompatibility. It was suggested that ZK60-3.6Nd was a preferable candidate for biodegradable bone implant.     

Mussel-inspired multifunctional coating for bacterial infection prevention and osteogenic induction

Bacterial infection and osteogenic integration are the two main problems that cause severe complications after surgeries. In this study, the antibacterial and osteogenic properties were simultaneously introduced in biomaterials, where copper nanoparticles(Cu NPs) were generated by in situ reductions of Cu ions into a mussel-inspired hyperbranched polyglycerol(MI-h PG) coating via a simple dip-coating method.This hyperbranched polyglycerol with 10 % catechol groups’ modification presents excellent antifouling property, which could effectively reduce bacteria adhesion on the surface. In this work, polycaprolactone(PCL) electrospun fiber membrane was selected as the substrate, which is commonly used in biomedical implants in bone regeneration and cardiovascular stents because of its good biocompatibility and easy post-modification. The as-fabricated Cu NPs-incorporated PCL membrane [PCL-(MI-h PG)-Cu NPs]was confirmed with effective antibacterial performance via in vitro antibacterial tests against Staphylococcus aureus(S. aureus), Escherichia coli(E. coli), and multi-resistant E. coli. In addition, the in vitro results demonstrated that osteogenic property of PCL-(MI-h PG)-Cu NPs was realized by upregulating the osteoblast-related gene expressions and protein activity. This study shows that antibacterial and osteogenic properties can be balanced in a surface coating by introducing Cu NPs.     

Antibacterial hydroxyapatite coatings on titanium dental implants

Titanium and its alloys are often used as substrates for dental implants due to their excellent mechanical properties and good biocompatibility. However, their ability to bind to neighboring bone is limited due to the lack of biological activity. At the same time, they show poor antibacterial ability which can easily cause bacterial infection and chronic inflammation, eventually resulting in implant failure. The preparation of composite hydroxyapatite coatings with antibacterial ability can effectively figure out these concerns. In this review, the research status and development trends of antibacterial hydroxyapatite coatings constructed on titanium and its alloys are analyzed and reviewed. This review may provide valuable reference for the preparation and application of high-performance and multi-functional dental implant coatings in the future.     

Effect of powder processing and alloying additions (Al/ZrB2) on the microstructure,mechanical and electrical properties of Cu

The present work elucidates the effect of powder processing conditions (milling/mixing) and conductive alloying element (Al: aluminium) and ceramic (ZrB₂: zirconium diboride) reinforcement addition on the densification, microstructure and electrical conductivity of copper (Cu) processed via hot pressing route. Disregard of alloying element/reinforcement/content or powders preparation method, the density of Cu materials varied between 92.16 and 99.76% ρ_th (theoretical density) after hot pressing at a low temperature of 500 °C. In case of Cu-Al alloys, the powder processing method significantly influenced its microstructure and conductivity. Particularly the Cu-Al alloys processed using mixed powders consisted of various phases Cu, α-Cu, γ₁ (Cu₉Al₄), δ (Cu₃Al₂), ζ₁ (Cu₄Al₃), η₂ (CuAl) and θ (CuAl₂) and the Cu alloys prepared using milled powders composed of either only α-Cu or α-Cu and γ₁ (Cu₉Al₄) phases (depending on the Al content). Whereas, only Cu and ZrB₂ phases were observed with the Cu-ZrB₂ composites processed using either milled or mixed powers. In case of Cu-Al alloys, the hardness (0.88–3.41 GPa) and strength (540.30–1120.18 MPa) of Cu increased with the addition of Al. Interestingly, the hardness (0.88–2.55 GPa) and strength (508.50–970.60 MPa) of Cu increased upto 5 wt% ZrB₂ and then they lowered with further addition of ZrB₂. In particular, the hardness and strength of Cu-ZrB₂ composites are lower than Cu-Al alloys reflecting the effectiveness of solid solution strengthening in the Cu alloys as compared to dispersion strengthening mechanism in Cu composite. The pure Cu prepared using milled powders exhibited low conductivity (75.70% IACS) than Cu processed using as-received/un-milled powders (97.00% IACS). Also, the Cu-ZrB₂ composites measured with better electrical conductivity than Cu-Al alloys. Depending on the milling conditions and alloying/reinforcement amount, the conductivity of Cu-ZrB₂ composites varied between 44.10 and 88.70% IACS.     

Enhanced resistance of 2205 Cu-bearing duplex stainless steel towards microbiologically influenced corrosion by marine aerobic Pseudomonas aeruginosa biofilms

An antibacterial 2205-Cu duplex stainless steel(DSS)was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu~(2+)ions from the2205-Cu DSS surface.In this work,the microbiologically influenced corrosion(MIC)resistance of 2205-Cu DSS in the presence of the corrosive marine bacterium Pseudomonas aeruginosa was investigated.The addition of copper improved the mechanical properties such as the yield strength,the tensile strength and the hardness of 2205 DSS.Electrochemical test results from linear polarization resistance(LPR),electrochemical impedance spectroscopy(EIS)and critical pitting temperature(CPT)measurements showed that 2205-Cu DSS possessed a larger polarization resistance(R_p),charge transfer resistance(R_(ct))and CPT values,indicating the excellent MIC resistance of 2205-Cu DSS against the corrosive P.aeruginosa biofilm.The live/dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS.The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14 d in the presence of P.aeruginosa(2.2μm vs 12.5μm).2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P.aeruginosa.     

In vitro degradation performance and biological response of a Mg-Zn-Zr alloy

The feasibility of a Mg-Zn-Zr alloy for biomedical applications was studied through microstructure characterization, corrosion tests in different biological media, and cell proliferation, differentiation and adhesion tests. Corrosion tests showed that the ZK60 alloy in the as-extruded state with finer grain sizes exhibited slower corrosion rates than the same alloy in the as-cast state. The tests in different biological fluids showed that the corrosion rates of the as-cast and as-extruded ZK60 alloy in DMEM + FBS were the highest, while those in Hank's solution were the lowest. The corrosion rate of the as-extruded ZK60 alloy was similar to the corrosion rates of other commercial magnesium alloys, namely the die-cast AZ91D, die-cast AM50, extruded AZ31 and extruded WE43 alloys. The results obtained from the indirect cytotoxicity evaluation showed that the 100% concentrated cast and extruded ZK60 alloy extracts resulted in significantly reduced cell numbers and total protein amounts, as compared to the negative control. The cell number and total protein amount increased with the gradual dilution of the extracts, but the protein normalized ALP activity showed an opposite trend. For the direct assay, L-929 and MG63 cells exhibited good adhesion with spread pseudopod on the surface of extruded ZK60 alloy samples after 24 h culture. In short, the as-extruded ZK60 alloy could be a good candidate material for biodegradable implants.     

Ni-Cu and Ni-Co alloys: Synthesis,structure, and catalytic activity for the decomposition of chlorinated hydrocarbons

Homogeneous Ni _x Cu_{1 ? x} and Ni _x Co_{1 ? x} (x = 0.90–0.99) alloys have been prepared through the coprecipitation of precursors (hydroxides or carbonates) and reduction of the precipitate. The formation of single-phase Ni _x M_{1 ? x} alloys in all of the samples has been confirmed by X-ray diffraction. We have assessed the catalytic activity of the alloys for 1,2-dichloroethane decomposition with carbon nanomaterial (CNM) formation. The highest catalytic activity (CNM yield, 26–27 g/g_cat) was offered by the nickel alloys containing ～1 at % Cu or Co. The carbon material obtained has the form of segmented submicron wires with high morphological uniformity.     

Microstructure and solidification behavior of Cu–Ni–Si alloys

The microstructure and solidification behavior of Cu–Ni–Si alloys with four different Cu contents was studied systematically under near-equilibrium solidification conditions. The microstructures of these Cu–Ni–Si alloys were characterized by SEM and the phase composition was identified by XRD analysis. The phase transition during the solidification process was studied by DTA under an Ar atmosphere. The results show that the microstructure and solidification behavior is closely related to the composition of Cu–Ni–Si alloys. The microstructure of Cu–Ni–Si alloys with higher than 40% Cu content consists of primary phase α-Cu(Ni, Si) and eutectic phase (β₁-Ni₃Si + α-Cu(Ni,Si).When the Cu content is about 40%, only the eutectic phase (β₁-Ni₃Si + α-Cu(Ni,Si)) is present. DTA analysis shows there are three phase transitions during every cooling cycle of alloys with higher than 40% Cu content, but only one for 40% Cu content. Cu–Ni–Si alloy with 40% Cu solidifies by a eutectic reaction, but Cu–Ni–Si alloys with higher than 40% Cu content solidify as a hypoeutectic reaction.     

Microstructures and mechanical properties of Mg–Zn–Zr–Dy wrought magnesium alloys

Microstructures and phase compositions of as-cast and extruded ZK60–xDy (x?= 0–5) alloys were analysed by optical microscope, scanning electron microscope, X-ray diffraction and differential scanning calorimetry. Meanwhile, the tensile mechanical property was tested. With increasing Dy content, Mg–Zn–Dy new phase increases gradually, while MgZn₂ phase decreases gradually to disappear. As-cast microstructure is refined gradually; meanwhile extruded one is refined further with decreasing average grain size to 1 μm for ZK60–4·32Dy alloy. Second phase, tending to distribute along grain boundary by continuous network in as-cast state, breaks and distributes dispersedly in extrusion state. As-cast tensile mechanical property remains almost unchanged at ambient temperature; however, extruded ones are enhanced significantly at ambient and elevated temperatures, respectively. Tensile strength at 298 and 473 K increases gradually from 355 and 120 MPa for ZK60 alloy to 395 and 171 MPa for ZK60–4·32Dy alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.     

Antibacterial and tribological properties of TaN–Cu,TaN–Ag,and TaN–(Ag,Cu) nanocomposite thin films

In this study, attempts were made to prepare and characterize TaN–(Cu,Ag) nanocomposite films by using a hybrid approach combining reactive co-sputtering and rapid thermal annealing at various temperatures to induce the formation of soft metal particles in the matrix or on the surface. The films’ properties and their antiwear and antibacteria behaviors were compared with those previously studied TaN–Cu and TaN–Ag films. All three types of TaN–(soft metal) films showed good tribological properties due to the lubricious Ag and/or Cu layers. It was also found that the antibacteria efficiency of TaN–(Ag,Cu) film against either Escherichia coli or Staphylococcus aureus could be much improved, comparing with that of TaN–Ag or TaN–Cu film. The synergistic effect due to the coexistence of Ag and Cu is obvious. The annealing temperature used to develop TaN–(Cu,Ag) films with good antibacterial and antiwear behaviors could be as low as 250 °C. The lowering of the annealing temperature made these films applicable onto low-melting-point materials, such as polymers.     

AlCu alloy films prepared by the thermal diffusion technique

100-nm thick films of Al_1 ? xCu_x alloys were prepared on glass substrates by thermal diffusion technique. The Cu atomic concentration was varied from 10% to 90%. Alloys were prepared at different temperatures into a vacuum oven with Argon atmosphere. Two thermal processes were used: i) heating the film at 400 °C in a single step, and ii) heating the films in sequential steps at 100, 200, 300 and 400 °C. Morphology, electrical resistivity, and crystalline orientation of the alloys were studied. The electrical resistivity and surface roughness of the alloys were found to depend strongly on the atomic composition and the diffusion temperature. However, we did not find differences between samples prepared under the two thermal processes. Alloys prepared with x = 0.6 and x = 0.1–0.3 as Cu at concentration exhibited values on electrical resistivity and surface roughness lower than pure Al. Different phases of the Al_1 ? xCu_x films were observed as a function of Cu concentration showing a good agreement with the AlCu phase diagram.     

Nanoparticle interactions with the magnesium alloy matrix during physical deformation: Tougher nanocomposites

This study is aimed at understanding the toughness enhancing function of nanoparticles in magnesium nanocomposites, focussing on experimentally observed nanoparticle–matrix interactions during physical deformation. Al₂O₃ nanoparticles were selected for reinforcement purposes due to the well known affinity between magnesium and oxygen. AZ31/AZ91 (hybrid alloy) and ZK60A magnesium alloys were reinforced with Al₂O₃ nanoparticles using solidification processing followed by hot extrusion. In tension, each nanocomposite exhibited higher ultimate strength and ductility than the corresponding monolithic alloy. However, the increase in ductility exhibited by ZK60A/Al₂O₃ (+170%) was significantly higher than that exhibited by AZ31/AZ91/Al₂O₃ (+99%). The previously unreported and novel formation of high strain zones (HSZs, from nanoparticle surfaces inclusive) during tensile deformation is highlighted here as a significant mechanism supporting ductility enhancement in ZK60A/Al₂O₃ (+170% enhanced) and AZ31/AZ91/Al₂O₃ (+99% enhanced) nanocomposites. Also, ZK60A/Al₂O₃ exhibited lower and higher compressive strength and ductility (respectively) compared to ZK60A while AZ31/AZ91/Al₂O₃ exhibited higher and unchanged compressive strength and ductility (respectively) compared to AZ31/AZ91. Here, the previously unreported nanograin formation (recrystallization) during room temperature compressive deformation as a toughening mechanism in relation to nanoparticle stimulated nucleation (NSN) ability is also highlighted.     

Effect of rare earth Y addition on the microstructure and mechanical properties of high entropy AlCoCrCuNiTi alloys

A series of AlCoCrCuNiTiY_x (x values in molar ratio, x = 0, 0.5, 0.8, 1.0) alloys have been prepared using vacuum arc melting. Classical high entropy diffraction peaks corresponding to a BCC crystal structure and some Cu, Cr peaks are observed for the AlCoCrCuNiTi alloy. However, with the incorporation of rare earth element Y, the BCC diffraction peaks disappeared and were replaced by new compounds like Cu₂Y and AlNi₂Ti. A typical cast dendrite structure with Cu-rich dendritic regions and Cr-rich rosette-like shape precipitations are found in the AlCoCrCuNiTi alloy. In the AlCoCrCuNiTiY_x alloys, Y segregated preferentially to Cu and combined as bulky Cu₂Y compound. The maximum stress of the AlCoCrCuNiTi alloy is 1495 MPa, but reduces intensively after the incorporation of Y due to the formation of bulky Cu₂Y. For all the alloys, the compressive fracture mechanism is observed to be cleavage fracture.     

Effect of substituting Ni with Cu on the cycle stability of La0.7Mg0.3Ni2.55−xCo0.45Cux (x = 0–0.4) electrode alloy prepared by casting and rapid quenching

In order to improve the cycle stability of the La–Mg–Ni system (PuNi₃-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Cu. Hydrogen storage alloys La_0.7Mg_0.3Ni_2.55−xCo_0.45Cu_x (x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and the quenching rate on the microstructures and the cycle stability of the as-cast and quenched alloys were investigated in detail. The results obtained by X-ray diffraction show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni₃ phase, the LaNi₅ phase and the LaNi₂ phase, and the amount of the LaNi₂ phase increased with the increase of the Cu content. The substitution and rapid quenching have an inappreciable influence on the phase compositions of the alloys, but both obviously changed the phase abundances of the alloys. The results derived by transmission electron microscopy confirm that the substitution of Cu for Ni is favourable for the formation of an amorphous phase in the as-quenched alloys. The results obtained by the electrochemical measurement indicate that substituting Ni with Cu improved the cycle stability. When the Cu content increases from 0 to 0.4, the cycle lives of the as-cast and rapidly solidified alloys increased from 72 cycles to 88 cycles and from 100 cycles to 122 cycles, respectively.     

In situ synthesized low modulus biomedical Zr-4Cu-xNb alloys

In order to develop new biomaterials for hard tissue replacements, the Zr-4Cu-xNb (x = 0, 0.3, 0.6 and 0.9) biomedical alloys with required properties were designed and prepared using vacuum arc melting method for the first time. Phase analysis and microstructure observation showed that all the as-cast Zr-4Cu-xNb samples consisted of α-Zr and Zr₃Cu. In addition, the lamellar eutectoid is found near the grain boundary. These alloys exhibited moderate compressive strength (1150–1300 MPa), yield stress (750–1000 MPa), favorable plastic strain (19%–27%), high elastic energy (11 MJ/m³–16 MJ/m³) and low Young's modulus (25 GPa–31 GPa). This good combination of mechanical properties indicates them potential biomedical materials for biological hard tissue replacements.     

Electronic structure of Cu100−xZrx (x = 40, 50, 60) metallic glasses

The electronic structure of Cu_100−xZr_x (x = 40, 50, 60) metallic glasses was investigated by ultraviolet photoelectron spectroscopy and X-ray photoemission spectroscopy, the valence band spectra of these alloys were analyzed by a large shift of the Cu d-band peaks to higher binding energies upon increasing Cu content. Photoemission experiments and first-principles calculations prove that the values of density of states at Fermi level of Cu_100−xZr_x metallic glasses are mainly dominated by Zr rather than Cu. This work will enlighten further research on understanding the inheritance of metallic glasses and designing new metallic glasses with unique properties.