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Amorphous metals have wide applications, including those in various transducer and sensor devices, because of their extraordinary physical and chemical characteristics, excellent mechanical propert...

Subsequent processing through machining for biocompatible Zr-based BMG previously developed is needed in order to enlarge the material application, especially for medical devices. In this study the performance of CuCr tool on EDM process was investigated to cut biocompatible Zr-based BMG having low machinability nature. The experiment utilized volume loss technique to measure the TWR and consecutive SEM observation to reveal the tool wear mechanism of selected tool samples. The tool wear behavior was strongly characterized by the combination of discharge current and pulse-on time, where the larger TWR obtained by higher current and shorter pulse-on time. By SEM analysis, the irregular-shaped surface morphology with the presence of debris was observed on the tool wear region resulted by high discharge energy process. Additionally, the larger crater size, microvoids and numerous debris particles were also appeared on BMG workpiece surface machined using higher discharge energy.

The machinability information of Zr-based bulk metallic glasses (BMGs) are recently limited but essential to provide technological recommendation for the fabrication of the medical devices due to the material’s metastable nature. This study aims to investigate the material removal rate (MRR) and surface roughness under different current and pulse-on time of newly developed Ni- and Cu-free Zr-based BMG using sinking-electrical discharge machining (EDM). By using weightloss calculation, surface roughness test and scanning electron microscopy (SEM) observation on the workpiece after machining, both MRR and surface roughness were obtained to be increased up to 0.594 mm3/min and 5.50 μm, respectively, when the higher current was applied. On the other hand, the longer pulse-on time shifted the Ra into the higher value but lower the MRR value to only 0.183 mm3/min at 150 μs. Contrary, the surface hardness value was enhanced by both higher current and pulse-on time applied during machining indicating different level of structural change after high-temperature spark exposure on the BMG surface. These phenomena are strongly related to the surface evaporation which characterize the formation of crater and recast layer in various thicknesses and morphologies as well as the crystallization under the different discharge energy and exposure time.

Bacterial infection remains a great risk in medical implantation surgery. In this paper, we found that degradable metals may be a feasible alternative option of antibacterial implantation materials. It is known that the spalling mechanism of magnesium (Mg) during degradation leads to Mg ions-induced alkaline environment, which is harmful to planktonic bacteria. In this study, we showed that alkaline pH environment is almost harmless to those adhesive bacteria protected in well-formed biofilms. Moreover, experimental results demonstrated that the biofilm formed in the place where Mg spalls are destroyed, releasing the covered bacteria to be planktonic in the alkaline environment. As a result, the colonization of biofilms continues to shrink during the degradation of Mg. It implies that if degradable metal is employed as implantation material, even if bacterial infection occurs, it may be possibly cured without second surgery.

A suture anchor is a medical device commonly used in rotator cuff repair surgery to attach tendons to the greater tuberosity of the humerus. Patient- and device-related factors, such as structural designs and poor bone density, can cause unsatisfactory clinical results. In this study, a new suture anchor design with four distinctive parameters was proposed, and the structural performance was optimized in a full factorial experimental design using finite element analysis. Two types of bone blocks—normal and osteoporotic bone—which received screw implants, were simulated to investigate the parametrical effects on various bone qualities. The prescribed motion at a constant removal velocity was used to evaluate the pullout strength. The von Mises criterion was employed in a force control simulation for topology optimization. Moreover, mechanical tests guided by ASTM-F543-17 were conducted for validation. This paper demonstrates the comprehensive process for developing a suture anchor with sufficient mechanical integrity for clinical use and clarifies the contributions of each distinctive design parameter in this application.

Most high-entropy alloys and medium-entropy alloys (MEAs) possess outstanding mechanical properties. In this study, a series of lightweight nonequiatomic Al50–Ti–Cr–Mn–V MEAs with a dual phase were produced through arc melting and drop casting. These cast alloys were composed of body-centered cubic and face-centered cubic phases. The density of all investigated MEAs was less than 5 g/cm3 in order to meet energy and transportation industry requirements. The effect of each element on the microstructure evolution and mechanical properties of these MEAs was investigated. All the MEAs demonstrated outstanding compressive strength, with no fractures observed after a compressive strain of 20%. Following the fine-tuning of the alloy composition, the Al50Ti20Cr10Mn15V5 MEA exhibited the most compressive strength (~1800 MPa) and ductility (~34%). A significant improvement in the mechanical compressive properties was achieved (strength of ~2000 MPa, strain of ~40%) after annealing (at 1000 °C for 0.5 h) and oil-quenching. With its extremely high specific compressive strength (452 MPa·g/cm3) and ductility, the lightweight Al50Ti20Cr10Mn15V5 MEA demonstrates good potential for energy or transportation applications in the future.

In this study, the various Sr(Ce0.6Zr0.4)0.9Y0.1O3-δ/YBaCo2O5+δ (SCZY/YBCO) composite ceramic membranes were prepared by sintering at different temperatures and used as proton membranes for hydrogen permeation. SCZY and YBCO powders were prepared by the citrate-ethylenediaminetetraacetic acid sol-gel process and solid-state reaction method, respectively. The chemical reaction, structure, morphology, thermal expansion, and electrical conductivity of SCZY/YBCO were investigated through X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermal mechanical analyzer (TMA) and direct current four-probe method. The relative sintered density of SCZY/YBCO membrane sintered at 1250 °C was as high as 99.5%. The conductivity of the SCZY/YBCO increased with the sintering temperature. The SCZY/YBCO sample sintered at 1250 °C exhibited the highest conductivity of 13.44 S/cm at 800 °C. The H2 permeability of the SCZY/YBCO membrane was 3.83 mL min−1 cm−2, much higher than that of SCZY at 800 °C (1.37 mL min−1 cm−2).

To enhance weldability, this study used a Nd:YAG laser (which produces a faster thermal cycle) in combination with a liquid cooling device (LCD) to spot weld (Zr53Al17Co29)99Ta1 BMG. Here, an LCD was employed to provide a variety of initial welding temperatures (IWTs), with progressively lower IWTs from room temperature (RT) to -5 °C. After the welding process, the microstructure evolution (including parent material (PM), heat affected zone (HAZ), and weld fusion zone (WFZ)), glass forming ability (GFA), and mechanical property (microhardness) of the laser-welded samples were investigated. The results showed that two types of crystallines were observed in the HAZ after RT welding. The GFA indicators of the welded samples and microhardness in the HAZ were affected significantly. When the IWT decreased to 0 °C, the crystalline phase in the HAZ and WFZ were barely noticeable which resulted in a softer HAZ; the GFA indicator of the welded sample was not substantially different than that of the PM.

The ZrCu-B2 phase can effectively increase the plasticity for some specified Zr based metallic glasses composite (BMGC) by transformation induced plasticity (TRIP) mechanism. However, large and non-uniformly distributed ZrCu-B2 phases usually precipitate in the Zr-based BMGC samples by conventional copper mold casting. Therefore, the concept of inoculation in conventional solidification process was applied to modify the size and distribution of ZrCu-B2 phase in this study. Ta particles (size of 5–30 μm) with 0–4.0 vol% were added into the Zr48Cu47·5Al4Co0.5 BMG matrix as the inoculant. Ta particles can act as nucleation seeds for precipitating a homogeneously distributed ZrCu-B2 phase in the matrix. Moreover, the ZrCu-B2 precipitate size can be further controlled by different solidification cooling rates. It is clearly to see that the ZrCu-B2 phase embedded in the amorphous matrix for the Zr48Cu47·5Al4Co0.5 cast rods added with 0–0.75 vol% Ta particle cast by a copper mold at −30 °C (243 K, or a cooling rate of 650 K/s). In addition, the ZrCu-B2 phase exhibits a round shape and relatively homogeneous distribution. The optimum processes BMGC can exhibit significantly improved mechanical properties (1890 MPa fracture stress and 14% plastic strain) in comparison with the base BMGC (1560 MPa fracture strength and 7.5% plastic strain).

Platelet-rich fibrin (PRF) is a natural fibrin meshwork material with multiple functions that are suitable for tissue engineering applications. PRF provides a suitable scaffold for critical-size bone defect treatment due to its platelet cytokines and rich growth factors. However, the structure of PRF not only promotes cell attachment but also, due to its density, provides a pool for cell migration into the PRF to facilitate regeneration. In our study, we used repeated freeze drying to enlarge the pores of PRF to engineer large-pore PRF (LPPRF), a type of PRF that has expanded pores for cell migration. Moreover, a biodegradable Mg ring was used to provide stability to bone defects and the release of Mg ions during degradation may enhance osteoconduction and osteoinduction. Our results revealed that cell migration was more extensive when LPPRF was used rather than when PRF was used and that LPPRF retained the growth factors present in PRF. Moreover, the Mg ions released from the Mg ring during degradation significantly enhanced the calcium deposition of MC3T3-E1 preosteoblasts. In the present study, a bone substitute comprising LPPRF combined with a Mg ring was demonstrated to have much potential for critical-size bone defect repair.

Intervertebral fusion surgery for spinal trauma, degeneration, and deformity correction is a major vertebral reconstruction operation. For most cages, the stiffness of the cage is high enough to cause stress concentration, leading to a stress shielding effect between the vertebral bones and the cages. The stress shielding effect affects the outcome after the reconstruction surgery, easily causing damage and leading to a higher risk of reoperation. A porous structure for the spinal fusion cage can effectively reduce the stiffness to obtain more comparative strength for the surrounding tissue. In this study, an intervertebral cage with a porous gradation structure was designed for Ti64ELI alloy powders bonded by the selective laser melting (SLM) process. The medical imaging software InVesalius and 3D surface reconstruction software Geomagic Studio 12 (Raindrop Geomagic Inc., Morrisville, NC, USA) were utilized to establish the vertebra model, and ANSYS Workbench 16 (Ansys Inc., Canonsburg, PA, USA) simulation software was used to simulate the stress and strain of the motions including vertical body-weighted compression, flexion, extension, lateral bending, and rotation. The intervertebral cage with a hollow cylinder had porosity values of 80–70–60–70–80% (from center to both top side and bottom side) and had porosity values of 60–70–80 (from outside to inside). In addition, according to the contact areas between the vertebras and cages, the shape of the cages can be custom-designed. The cages underwent fatigue tests by following ASTM F2077-17. Then, mechanical property simulations of the cages were conducted for a comparison with the commercially available cages from three companies: Zimmer (Zimmer Biomet Holdings, Inc., Warsaw, IN, USA), Ulrich (Germany), and B. Braun (Germany). The results show that the stress and strain distribution of the cages are consistent with the ones of human bone, and show a uniform stress distribution, which can reduce stress concentration.

A series of biocompatible high-porosity (up to 72.4%) TiZr-based porous bulk metallic glass (BMG) scaffolds were successfully fabricated by hot pressing a mixture of toxic element-free TiZr-based BMG powder and an Al particle space holder. The morphology of the fabricated scaffolds was similar to that of human bones, with pore sizes ranging from 75 to 250 μm. X-ray diffraction patterns and transmission electron microscopy images indicated that the amorphous structure of the TiZr-based BMG scaffolds remained in the amorphous state after hot pressing. Noncytotoxicity and extracellular calcium deposition of the TiZr-based BMG scaffolds at porosities of 32.8%, 48.8%, and 64.0% were examined by using the direct contact method. The results showed that the BMG scaffolds possess high cell viability and extracellular calcium deposition with average cell survival and deposition rates of approximately 170.1% and 130.9%, respectively. In addition, the resulting TiZr-based BMG scaffolds exhibited a considerable reduction in Young’s moduli from 56.4 to 2.3 GPa, compressive strength from 979 to 19 MPa, and bending strength from 157 MPa to 49 MPa when the porosity was gradually increased from 2.0% to 72.4%. Based on the aforementioned specific characteristics, TiZr-based BMG scaffolds can be considered as potential candidates for biomedical applications in the human body.

In this study, creep behavior of the face-centered-cubic (FCC) {111} and {100} grains in single-phase Fe20Co20Ni20Cr20Mn20 and dual-phase Fe18Co18Ni20Cr18Mn18Al8 high-entropy alloys (HEAs) was evaluated using a nanoindentation method over temperatures range of 300–600 °C. We measured the creep response of the two different grain orientations in the two alloys in order to study the orientation and solid-solution effects. Creep stress exponent (∼3.8–5.0) and activation energy (240–260 kJ/mol) were extracted and analyzed from stain rate-stress and stain rate-temperature data to provide information on the creep mechanism. The results indicated that creep was controlled by dislocation climb in both alloys at both orientations. However, we pointed out that, based upon activation energy value alone, it was difficult to identify which elemental constituent would be the dominant diffusing species responsible for vacancy diffusion during the climb. It was found that creep activation volume for the current two HEAs (140 A3 or ∼12Ω, where Ω is the atomic volume) at 600 °C is larger than that reported for the Ni-based superalloys (∼50–100 A3 or less) within a similar temperature range. The significance of this larger activation volume is also discussed.

The oxidation of (Fe41Cr15Mo14C12B9Co7Y2)97Ta3 bulk metallic glass (Fe8-BMG) was investigated in dry air at 500–625 °C. The results showed that the oxidation kinetics of the alloy obeyed the parabolic rate law at T ≥ 550 °C, while the mass gain at 500 °C was extremely small. The oxidation rates of Fe8-BMG increased progressively as the temperature rose, especially when having its value at 600 °C which was comparable to that of the commercial 304L stainless steel. The scales formed on the amorphous steel consisted of granular Cr2O3, and its grain size increased with increasing temperature.

Mg-based bulk metallic glass has become a candidate material for orthopedic implant applications due to its biocompatibility, controllable degradation rate, osteoconductivity, and osteoinductivity. However, this glass matrix is too brittle, which limits further application in medicine. To enhance such plasticity, we used an ex-situ method to add porous Mo particles to the Mg-based bulk metallic glass matrix to induce the branching of the primary shear band into multiple secondary shear bands. Our results revealed that ex-situ porous Mo particles can enhance plasticity in multiple dimensions and different structures of Mg-based bulk metallic glass. Moreover, these additional Mo particles did not impair the biocompatibility and biological function of preosteoblasts.

Metal solutions, such as high- and medium-entropy alloys, exhibit extraordinary mechanical performance in comparison to regular alloys. In this study, we employ a crystal plasticity finite element model (CPFEM) to study the strengthening mechanisms of a new medium-entropy alloy, Ti65(AlCrNb)35. A 3D representative model is constructed by processing experimental results for Ti65(AlCrNb)35, such as average grain size, grain size distribution, and initial texture, using the open-source software Dream.3D. The constitutive law for the grains is described by the crystal plasticity and implemented in Abaqus user-defined material (UMAT). The results of uniaxial tensile tests are utilized to calibrate the required parameters in the CPFEM. Strengthening effects resulting from the grain size, strain rate, and cyclic loading for Ti65(AlCrNb)35 are investigated by performing numerical simulations based on the proposed computational framework. Numerical simulation results show that the yield strength increases with decreasing initial grain size, which agrees well with experimental observations of the Hall–Petch effect. In addition, the rate-dependent yield stress increases as the applied strain rate increases in the tensile tests. Moreover, the cyclic loading results demonstrate the isotropic hardening behaviors and the saturation of yielding strength when the maximum strain reaches 10%. Finally, we discuss the contributions of different strengthening mechanisms on the yield strength of Ti65(AlCrNb)35 under different load conditions.

Using the CALPHAD method, lightweight nonequiatomic Ti60(Al)x(VCrNb)40-x (x = 6, 8, 10, 12, and 18 at.%) medium-entropy alloys (MEAs) were designed and produced using vacuum arc melting and drop casting. The density of these cast alloys decreased with an increase in Al concentration from 5.45 to 4.79 g cm−3. All of these cast alloys exhibited a body-centered cubic (BCC) microstructure. However, a nanosized ordered B2 phase was identified in the cast alloys with higher Al concentrations (Al-12 and Al-18). The prediction of BCC phase formation using CALPHAD was consistent with the experimental results. These BCC-structured alloys can withstand over 50% strain at room temperature, which demonstrates excellent compressive ductility. Moreover, the results demonstrate that the as-cast Al-6 and Al-8 samples had superior plasticity under tensile testing, with a tensile strength of 1120 MPa and approximately 30% plastic strain. Furthermore, with an increase in Al concentration, the alloys exhibited a notable trend in yield strength and a decreasing trend in plastic strain. The change in mechanical properties of these MEAs caused by the formation of B2 nanoparticles was also investigated.

In this study, Sr(Ce 0.6 Zr 0.4 ) 1−x Y x O 3−δ (x = 0.1, 0.15, 0.2, 0.25, 0.3, SCZY) perovskite proton-conducting ceramics were synthesized using the citrate-ethylenediaminetetraacetic acid complexing method. The effect of the Y concentration on the crystal structure, electrochemical performance and hydrogen flux of the SCZY samples in air and a H 2 atmosphere were investigated. The sintered SCZY samples showed a main perovskite crystal structure with several SrY 2 O 4 impurity phases when x ≥ 0.20. The grain size of SCZY samples when x = 0.25 and 0.30 was smaller than that of other samples. The conductivity of all samples increased as the temperature increased in both air and H 2 ; however, the conductivity of SCZY in H 2 was lower than that in air. The results of AC impedance, demonstrated that resistance mainly derived from the charge transfer, which was apparently higher than the bulk and grain boundary resistance. Sr(Ce 0.6 Zr 0.4 ) 0.85 Y 0.15 O 3-δ exhibited low charge transfer resistance in both air and the H 2 atmosphere and had a high hydrogen flux of 0.34 ml min −1 cm −2 μm −1 at 800 °C. The structures of all SCZY samples were stable in 80 °C water.

Study on biomaterials is recently essential for rapid development of medical application and Zr 54 Al 17 Co 29 BMGbecomes promising candidate due to the lack of toxic elements. Partial crystallization by isothermal annealing at SCL region was used to variate the crystallinities of BMG. The structural and thermal properties of as cast and partially crystallized samples were confirmed by XRD and DSC test, while microvickers and compression test were further utilized to investigate their mechanical properties. By the higher crystallinity, the hardness could be slightly increased in range 540 ± 5 to 575 ± 5 H v. As-cast sample shows the yield strength and plastic strain of 2130 ± 75 MPa and 2.2 ± 1.6%. The yield strength is increased by the presence of 10% nanocrystal, afterwards, fall and raise phenomena are obtained with further crystallinity. However, with higher crystallinity, the plasticity is significantly degraded and no more plastic strain observed at sample with 50% of crystallinity. Both the presence of nanocrystalline phase and free volume annihilation are the reason of mechanical properties change on the Zr-based BMG.

The 3D printed bulk samples fabricated by selective laser melting (SLM) of the additive manufacturing technique are usually considered to be 3D isotropic in microstructures and mechanical responses. This study systematically investigates the anisotropic responses in terms of hardness and electrochemical resistance for the X-, Y- and Z-planes of the SLM Ti-6Al-4V bulk samples fabricated with the zigzag laser path strategy. Results show that all SLM planes exhibit no significant difference in Young's modulus compared to the mechanically rolled plate. However, the X-plane, referred to the cross-sectional plane perpendicular to the laser moving direction, is found ~20% lower hardness and the lowest corrosion resistance compared to the Y- and Z-planes. The underlying reasoning is researched and discussed. The microstructure observations indicate that artifact holes are induced in the X-plane due to un-uniform laser intensity distribution between two neighboring printing lines. Alternatively, the Y- and Z-planes exhibit dense morphology due to multiple heating while zigzag scanning. Experimental results also indicate that the SLM materials exhibit higher corrosion resistance than the commercial rolled materials.

Electrochemical corrosion of as-cast and annealed zirconium-based bulk metallic glass (BMG) Zr48Cu36Al8Ag8 in 0.1 M NaCl solution was investigated in this work. The as-cast specimen, in complete amorphous form, contained null percent of crystal phase (denoted as 0C); however, the annealed ones contained 11, 25, 50, 75 and 100 % crystal phase (denoted as 11C, 25C, 50C, 75C and 100C, respectively) determined by the annealing duration of 0C specimen at 471 °C. Through monitoring of open circuit potential (OCP), measurements of direct-current polarization resistance (PR), Tafel plot (TP), cyclic anodic potentiodynamic polarization (CAPD), and electrochemical impedance spectroscopy (EIS), we found that the corrosion behavior of the Zr48Cu36Al8Ag8 was detremined by the the crystal phase present in the specemns dominated by the annealing durations. The corrosion resistance decreased in the order: 25C > 11C > 0C > 50C > 75C > 100C. This result revealed that the corrosion resistance inclined to be better and reached a mxmium with increasing the percentgae of the crystal phase from 0 to 25%; however, it decreased with further increasing the crystal phase over 25%. A corrosion mechanism is proposed to rationalize the sequence of corrosion resistance. According to the mechanism, the remained free volume and residual strain energy are responsible for the specimens containing crystal phase less than 25% (i.e., 0C, 11C and 25C); whereas crystal defects such as grain boundaries governed the corrosion of those containing crystal phase more than 25 % (i.e., 50C, 75C and 100C).

The incipient plasticity and creep behavior of body-centered cubic (BCC) Ti65(AlCrNb)35 medium entropy alloy (MEA) were investigated via nanoindentation. The elastic modulus and hardness obtained from different methods were compared. The activation volume for plastic deformation was calculated to be 11 b3, indicating a larger-scaled Peierls deformation mechanism typical for BCC metals. The orientation effect on incipient plasticity was studied on (100), (110) and (111) orientations at room temperature. The orientation difference is attributed to the different Schmid factors for different planes. The activation volume and activation energy of dislocation nucleation on Ti65(AlCrNb)35 was estimated as 0.8–0.9 b3 and 0.43 eV, which suggests that the mechanism of incipient plasticity is heterogeneous dislocation nucleation assisted by pre-exist defects, with a very localized activated volume. Also, the activation volume and energy of Ti65(AlCrNb)35 are higher than those of conventional metals (Ni, Pt, Cr and Mg) and lower than those of high entropy alloys (HEAs), which suggests that the dislocation nucleation in Ti65(AlCrNb)35 is more difficult than that in metals but easier than that in HEAs. Creep responses of the (100), (110) and (111) grains at 500–600 °C were found to be all dominated by the power-law dislocation creep mechanism (stress exponent n ~ 5) with the activation energy ~130 kJ/mol. The high stress applied by the indenter tip led to the stress-induced pipe diffusion, assisting the dislocation climb and lowering the activation energy. The activation volume was measured as 3–6 b3, related to dislocation climb and atom diffusion at elevated temperatures. The creep displacements and creep rates for the (100), (110) and (111) planes are quite similar, probably resulting from (i) complex slip systems in BCC structure underneath the indenter tip, (ii) a complex strain field produced by concentrated solute atoms, and (iii) the stress-induced pipe diffusion.

Recently, the Ti-6Al-4V alloy fabricated by laser powder bed fusion has been widely studies. According to the high cooling rate, the strength of 3D printed Ti-6Al-4V alloy usually higher than that made by traditional process. In the meanwhile, the residual stress or microstructure feature that caused by high cooling rate usually causes the lower ductility. Therefore, such defects of these Ti-based alloys should be prevented before the application. Besides the porosity, the overall ductility of Ti-based alloys is consisted of its microstructure, of which dominated by acicular α′ structure with some dislocations or twins. Namely, an important effect on ductility is the α′ phase decomposed into the α phase and β phase. In present researches, some various heat treatment conditions are performed, and to investigate the relationship between their microstructures and mechanical properties. By proper heat treatment, the temperature of martensitic transition (Ms) temperature was between 750 and 800 °C, which is lower than the traditional cast/wrought Ti-6Al-4V alloy. Moreover, through the identification of XRD and TEM, there is a α’→α + β transformation and some island β-phase particles formed at the acicular α phase interface. It is also shown that the residual stress can be eliminated after annealed at 600 °C for various times resulting to increase the overall elongation about 3–5% without significantly reducing the strength.

The (Ti40Zr10Cu36Pd14)100 − xSix (x = 0, 0·5, 1·0, 1·5) bulk metallic glass (BMG) rods with a diameter of 2–4 mm have been successfully fabricated by suction casting method and characterised. The X-ray diffraction results reveal that these entire (Ti40Zr10Cu36Pd14)100 − xSix alloy rods exhibit a typical amorphous diffraction pattern with only a broad maximum at 2θ∼40°. The optimum glass forming ability values γ and γm (0·430 and 0·774 respectively) occur at the (Ti40Zr10Cu36Pd14)99·5Si0·5 amorphous alloy. This suggests that the Si element present a positive effect on increasing glass forming ability in the Ti40Zr10Cu36Pd14 alloy system. The hardness of these Ti based BMGs exhibits an increasing trend with Si addition and saturated ∼710 HV. In addition, the result of compression test shows that the optimum mechanical property occurs at the (Ti40Zr10Cu36Pd14)99·5Si0·5 amorphous alloy, which presents 2050 MPa fracture strength and 8% failure strain.

In this study, proton-conducting Sr(Ce0.6Zr0.4)0.85Y0.15O3−δ perovskite is synthesized using the citrate-ethylenediaminetetraacetic acid (EDTA) complexing method. The crystal structure, sintering behavior, coefficient of thermal expansion (CTE), electrical conductivity, electrochemical performance and hydrogen permeation of the Sr(Ce0.6Zr0.4)0.85Y0.15O3−δ is determined for various atmospheres and partial pressures of water. Sr(Ce0.6Zr0.4)0.85Y0.15O3−δ is extremely dense after sintering at 1450 °C for 6 h. The structure of the Sr(Ce0.6Zr0.4)0.85Y0.15O3−δ does not change after heat treatment in a hydrogen atmosphere at a partial pressure of water of 4.93 × 10−2 atm. The CTE of the Sr(Ce0.6Zr0.4)0.85Y0.15O3−δ at temperature of 100–900 °C is 11.4 × 10−6 K−1. The electrical conductivity of the sample is 0.012 S cm−1 at 900 °C. The hydrogen permeation flux increases from 0.1 to 0.184 mmol min−1 cm−2 as the temperature increases from 500 °C to 800 °C.

Zr-based thin film metallic glass (TFMG), exhibiting the unique properties of good glass forming ability (GFA), corrosion resistance, and biocompatibility, can be applied in various novel fields of industries. An ultra-smooth surface is obtained with the TFMG coatings, which is beneficial to modify the work surface. Thus, TFMG can be extended to medical appliances, such as surgical blades and micro-surgery scissors. The aims of this study are to fabricate the Cu-containing Zr-based TFMG onto SUS304 plates and to investigate the surface physical properties and their antimicrobial effects. The chemical compositions of Zr–Cu–Ni–Al coatings are examined by a field emission electron probe micro-analyzer (FE-EPMA). The amorphous structures of all TFMG are characterized by the X-ray diffractometry. The surface properties are analyzed by an atomic force microscope (AFM) and a water contact angle goniometer for the 304 stainless steel substrate and Zr–Cu–Ni–Al TFMG. Liquid culture methods and plate counting methods are used to assess the antimicrobial performance of specimens. The antimicrobial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under the Japanese Industrial Standard JIS Z2801: 2000 is over 99%. The release of copper ion from TFMG specimen is determined by the inductively coupled plasma-mass spectrometer (ICP-MS) to evaluate the antimicrobial activity of Cu-containing Zr-based TFMG. The results show that the surface of SUS 304 stainless steel substrate can be modified with deposited Zr–Cu–Ni–Al TFMG, and their improved antimicrobial efficacy against those bacteria is attributed to their amorphous rough surface, hydrophobic properties and released copper ion. The TFMG developed in this study with adequate hardness, good adhesion ability and antimicrobial efficiencies can be used as a promising candidate to improve the surface properties of the medical appliances and also to reduce the possibility of nosocomial infection.

For further enhancing the fatigue properties of high-strength aluminum alloy, the coating, which was combined with a layer of 200 nm ZrCu-based metallic glass thin film (MGTF) coupled with 50 nm titanium thin film buffer layer, was applied to coat on the surface of 7075-T6 aluminum alloy by the DC sputtering method. The results show that the fatigue limit could be significantly improved from 150 MPa for the uncoated sample to 250 MPa (66.7% increase) for the samples coated with ZrCu-based MGTF. In parallel, the fatigue life of 7075-T6 aluminum alloy with ZrCu-based MGTF could be drastically improved 45 times at a stress level of 250 MPa than the bare one. The outstanding mechanical properties of ZrCu-based MGTF, such as high strength and good adhesion between the film and the substrate, are the key factors to enhance the fatigue resistance of the coated aluminum alloy.

To demonstrate the effect of processing on the microstructure and subsequent mechanical property of bulk metallic glasses, we prepared two alloys, Cu 47.5 Zr 47.5 Al 5 and Cu 47.5 Zr 48 Al 4 Co 0.5 , using two different designs of suction mold – one with a sharp inlet and one with a blunt inlet. The two alloys have been demonstrated previously to be ductile via phase transformation of the B2 phase and twin formation during plastic deformation. Microstructures of the as-cast as well plastically deformed samples, in particular, the size and distribution of the B2 phase, were examined using X-ray diffraction, scanning and transmission electron microscopy. Compressive tests were conducted on samples cast by different molds and their properties were found to closely correlate with the B2 morphology. Fluid dynamics during suction casting was also analyzed. Effects of Vena contracta, flow velocity, and Reynolds number were discussed and compared favorably with experimental observations.

A prominent Fe-base bulk amorphous steel (BAS) alloy which presents high glass forming ability (GFA), good corrosion resistance, superior mechanical properties and relative lower cost. The Fe 41 Cr 15 Co 7 Mo 14 C 21 − x B x Y 2 ( x = 5–10) BAS rods with a diameter of 2–6 mm, can be fabricated by the suction casting method. The highest GFA value can be obtained by adjusting the ratio of boron/carbon, reaching to the value of γ = 0.4 and γ m = 0.69 for the alloy composition of Fe 41 Ce 15 Co 7 Mo 14 C 12 B 9 Y 2 . Meanwhile, this alloy also presents very large supercooled liquid region up to 81 K, favourable to be fabricated into micro-surgery tools by thermoplastic forming. In addition, the Fe-base BAS alloy exhibits extremely high hardness around 1200 Hv. The anodic polarization measurement of the Fe-based BAS exhibits a higher corrosion resistance than 304 SS and 316 SS in the Hank’s balanced salt solution. The sharpness test results reveal that the Fe-based BAS blade exhibits much higher sharpness because of its lower surface roughness and higher hardness. Moreover, the Fe-base BAS blade presents much better durability on cutting testing, it can remain relatively sharper edge-tip with a low blade sharpness index (BSI) value of 0.38 (in comparison with the BSI value of 0.59 for commercial blades) after the cutting testing over 50 cm length.

This paper presents a rapid screening process to select potential titanium and zirconium based metallic glasses (MGs) for bio-material applications. Electrochemical activity of 7 MGs including 6 bulk metallic glasses and 1 thin-film deposited MG in simulation body and human serum is first inspected. A low-voltage potential state test is also developed to simulate the cell membrane potential that the implant MGs will suffer. Results show that the MGs composed of Ti65Si15Ta10Zr10 and Ta57Zr23Cu12Ti8 exhibit excellent electrochemical stability in both simulation body fluid and human serum. In addition, the copper content in the MGs plays an important role on the electrochemical activity. MGs with the copper content higher than 17.5% show significant electrochemical responses. The cytotoxicity of the solid MG samples and the corrosion released ions are also evaluated by an in-vitro MTT test utilizing the murine bone marrow stem cells. Results indicate that all the solid MG samples show no acute cytotoxicity yet the corrosion released ions show significant toxicity for murine bone marrow stem cells. The rapid screening process developed in the present study suggests that the Ti65Si15Ta10Zr10 metallic glass has high potential for biomedical applications due to its good electrochemical stability and very low cytotoxicity.

To study the interfacial reaction of the ex-situ reinforced phase (Ta) of a Zr-based ((Zr48Cu36Al8Ag8)Si0.75 + Ta5) bulk metallic glass composite after laser spot welding, the interfacial regions of the reinforced phases located at specific zones in the welds including the parent material, weld fusion zone and heat affected zone were investigated. Specimen preparation from the specific zones for transmission electron microscopy analysis was performed using the focused ion beam technique. The test results showed that the reinforced phases in the parent material, weld fusion zone and heat affected zone were all covered by an interfacial layer. From microstructure analysis, and referring to the phase diagram, it was clear that the thin layers are an intermetallic compound ZrCu phase. However, due to their different formation processes, those layers show the different morphologies or thicknesses.

In order to improve the fatigue life of high strength aluminum alloy, a protection coating with 200 nm Zr-based metallic glass thin film (MGTF) coupled with 50 nm titanium thin film buffer layer was coated on the 7075-T6 aluminum alloy by DC sputtering. The results of four-point-bending fatigue test revealed that the fatigue life of 7075-T6 aluminum alloy with Zr-based MGTF could be improved by 30 times at a stress level of 250 MPa. The improvement of Zr-based MGTF coated samples in fatigue limit was 235 MPa (56.7% increase) in comparison with 150 MPa for the uncoated samples. The superior mechanical properties of Zr-based MGTF, such as high strength and good bending ductility, lower surface roughness, good adhesion between the film and the substrate, and high compressive residual stress are the key factors to improve the fatigue resistance of the coated aluminum alloy.

The bio-electrochemical response in simulated body fluid of the Zr53Cu30Ni9Al8 metallic glasses with different degrees of partial crystallization was systematically examined and discussed. Through thermal annealing, the volume fractions of the crystalline phases are determined to be 0, 34, 63, and near 100%. Based on the bio-corrosion voltage and current, as well as the polarization resistance, it is concluded that the fully amorphous alloy exhibits the highest bio-electrochemical resistance. With an increasing degree of partial crystallization, the corrosion resistance becomes progressively degraded. The passive current reveals that the fully amorphous metallic glasses can form a more protective and denser passive film on the metallic glass surface. The formation of reactive nanocrystalline phases in the amorphous matrix would reduce the bio-corrosion resistance.

article i nfo In this study, the structural and nanomechanical properties of Ga-doped ZnO (GZO) thin films on glass sub- strates followed by rapid thermal annealing (RTA) process were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation techniques. The XRD results indicated that the annealed GZO thin films are textured, having a preferential crystallographic orientation along the hexagonal wurtzite (002) axis. Both the grain size and surface roughness of the annealed GZO thin films exhibit an in- creasing trend after RTA treatment. The hardness and Young's modulus of the annealed GZO thin films were measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option. Furthermore, the hardness and Young's modulus were found to increase with increasing grain size when the RTA time was prolonged from 0.5 to 3 min. The deformation behavior is referred to the inverse Hall-Petch effect commonly observed in systems deformed primarily via grain boundary sliding. The sup- pression of dislocation movement-associated deformation mechanism might be arisen from strong pinning effects introduced by Ga-doping.

This study aims to develop a new Ta–Zr–Cu–Al–Ag thin film metallic glass (TFMG). The Zr–Cu–Al–Ag TFMGs were fabricated by co-sputtering of a Zr–Cu–Al–Ag bulk metallic glass target and a 99.9 at.% Ta target, which was controlled under various DC power. A bipolar pulsed DC power unit was connected to the Zr–Cu–Al–Ag bulk metallic glass (BMG) target to avoid arcing. The chemical compositions of Ta–Zr–Cu–Al–Ag TFMGs were examined by an electron probe microanalyzer (EPMA). Nanoindentation and nanoscratch tests were adopted to evaluate the hardness, elastic modulus and adhesion properties of the TFMGs. The amorphous structures of all TFMGs were characterized by the X-ray diffractometry and transmission electron microscope. It was found that the Ta content ranging from 26 to 63 at.% played an important role in the mechanical properties of the TFMGs. Abrupt enhancements of the hardness and elastic modulus were observed for this Ta-based TFMGs as compared with the Zr–Cu–Al–Ag TFMG. Relative atomic distance calculated from the XRD patterns reached a good agreement with the trend of variation of elastic modulus. The values of critical loads, LC1 and LC2, increased with Ta contents in the Ta–Zr–Cu–Al–Ag TFMGs. In addition, the lighter and shorter crack was found for the Ta–Zr–Cu–Al–Ag TFMGs with higher Ta content. The crack propagation resistance (CPR) value was applied to probe the toughness of TFMG semi-quantitatively, revealing that TFMG with 63 at.% Ta possessed a CPR value six times higher than that of the TFMG with 26 at.% Ta.

A series of open-cell bulk metallic glass foams (BMGFs) with different porosity content from 46% to 75% were successfully fabricated by a space holder technique. Morphologies of the foam, the amorphous nature and mechanical properties were systematically investigated by a combination of scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning carlorimetry (DSC), and compression test. The BMGFs possess Young's moduli ranging from 4 to 21 GPa and yield strength within 65–231 MPa, matching well with the moduli as well as yield strength of human bones and the predictions from theoretical models. These BMGFs are promising for bio-implant application without significant stress shielding effect.

A novel Ni-free Zr–Cu–Ag–Al ((Zr 48 Cu 36 Ag 8 Al 8 )Si 0.75 ) and a Zr–Cu–Ni–Al ((Zr 53 Cu 30 Ni 9 Al 8 )Si 0.5 ) bulk metallic glass (BMG), for comparison, were employed for Nd:YAG laser spot welding with three pre-selected energy inputs, including a low (6.2 J), a medium (8.0 J) and a high (9.2 J) energy input. After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's microhardness test. The results showed the Zr–Cu–Ag–Al BMG has better weldability than the Zr–Cu–Ni–Al BMG. No crystallization was observed in the weld fusion zones (WFZs) or heat-affected zones (HAZs) of the welds under three pre-selected energy inputs. Therefore, the GFA indices of Δ T x (Δ T x = T x − T g , T x is the crystallization temperature and T g is the glass transition temperature), γ ( γ = T x /( T g + T l ), T l is the liquidus temperature) and γ m ( γ m = (2 T x − T g )/ T l ), and the mechanical properties of the Zr–Cu–Ag–Al BMG welds did not differ significantly in comparison to the parent material (PM). For Zr–Cu–Ni–Al BMG, HAZ crystallization was unavoidable when a lower energy input was used; therefore, the GFA indices and mechanical properties of the weld were affected. Furthermore, when the GFA indices, Δ T x , γ and γ m , were used to predict the thermal stability of the BMG HAZs, Δ T x seemed to correspond more directly to the HAZ crystallization behaviors in this study. It was observed that the Δ T x value of Zr–Cu–Ag–Al BMG was about 26% higher compared to that of Zr–Cu–Ni–Al BMG.

The Ti/Zr-based metallic glasses (MGs) with various Cu contents are prepared, with nominal compositions of Ti45Zr40Si15 (Cu-free), Ti45Zr40Si10Cu5 (low-Cu), and Ti45Zr20Cu35 (high-Cu). The mechanical properties, corrosion resistance, and in-vitro biocompatibility of these MGs are investigated by means of nano-indentation, electrochemical analyses, MTS assays and inductively coupled plasma mass spectrometry, as well as in-vivo biocompatibility in terms of scanning electron microscopy, micro-CT scans and histological observations. The results show that the electrochemical activity and biocompatibility of the MGs are sensitive to the Cu content. Following the electrocorrosion tests, an increase in ion concentration is observed in high-Cu MG. Eight independent in-vitro tests show that the higher ion concentration leads to a lower cell viability. The twelve-week in-vivo tests show that the Cu-free MGs can be a promising material for developing bio-implants. The high-Cu MG would release Ti and Zr ions with insignificant Cu ion following corrosion testing, enhancing an increased local osteoclast activity.

Additive manufacturing (AM) has the advantages of fabricating complex models for application. In this study, cube structure with various porosity is manufactured by AM of selective laser melting (SLM). CAD software is used to create the micro porosity of sample models from 60 %∼80 %. The models are printed by Ti-6Al-4V powders. The morphology of the printed porous structures are examined by OM and SEM. Results show that only minor geometric deviation between the designed CAD pattern and the printed samples.

This paper presents the in-vitro and electrochemical investigations of four metallic glasses (MGs) for finding potential MG-based bio-materials. The simulation body-fluid Hanks solution is utilized for testing the corrosion resistance of MGs, and microorganisms of Escherichia coli are used in testing the bio-toxicity. In addition, a simple cyclic voltammetry method is used for rapid verification of the potential electrochemical responses. It is found that the Zr-based MG can sustain in the body-fluid, exhibiting the best corrosion resistance and electrochemical stability. The microbiologic test shows that E. coli can grow on the surface of the Zr-based metallic glass, confirming the low cell toxicity of this Zr-based MG.

Zr-based bulk metallic glasses (BMGs) possess excellent unique properties, such as high mechanical properties, good corrosion resistance, long-term antimicrobial ability, and were considered as an ideal candidate for medical tools. In this study, self-made ZrCuAlAgSi BMG surgical blade and commercial martensitic steel blade with and without metallic glass thin film (MGTF) were carefully examined for their sharpness. The amorphous state of BMG and MGTF were ascertained by X-ray diffraction (XRD) and differential scanning carlorimetry (DSC) analysis. A specially designed indentation-cutting rig was established to evaluate the sharpness of each blade on cutting the soft rubber material. The sharpness was evaluated by the blade sharpness index (BSI) which represents the ratio of external work done by the load to the energy required to initiate a cut or crack inside given materials. Results of sharpness test reveal that both BMG blade and the MGTF coated blade exhibits much lower surface roughness at their tip-edge and smaller BSI values (0.25 and 0.23, respectively) than the commercial blade (∼0.34), which corresponds to 26.5% and 32% improvement on the sharpness, respectively.

The microstructure and magnetic properties of the amorphous Co-Fe-Zr-B thin films grown on glass substrates by dc magnetron sputtering are investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) techniques. The Co-Fe-Zr-B thin films deposited at room temperature were annealed at temperatures ranged from 683 K to 773 K. Experimental results indicated that the coercivity (Hc) of the Co-Fe-Zr-B thin films is significantly influenced by residual stress and crystalline phases within the films. The correlation of the coercivity and the microstructure of Co-Fe-Zr-B thin films are discussed. After annealed at 683 K, the coercivity of the Co-Fe-Zr-B film was as low as 1.2 Oe.

Mg58Cu28.5Gd11Ag2.5 bulk metallic glass composites (BMGCs) dispersion strengthened by spherical Ti particles with different volume fractions and particle sizes were synthesized by injection casting and characterized. The presence of spherical Ti particles could highly absorb the energy of shear banding and branch the primary shear band into multiple shear bands, thus decrease the stress concentration for further propagation of shear band and so as to significantly enhance plasticity. In addition, owing to the good bonding of interface between Ti particle and amorphous matrix, the yield strength can be kept at 800 MPa as increasing the addition of Ti particles to 40 vol.%. Additionally, It was found for a given volume fraction of Ti particles, smaller particles would lead to shorter interparticle spacings, smaller confinement zone sizes than the larger particles, and consequently improve the compression plasticity from 12% plastic strain (for the BMGC with Vf = 40% and particle size (D) = 89 ± 20 μm) up to 25% strain (for the BMGC with Vf = 40% and D = 50 ± 17 μm).Also, for a given Ti particle size, higher volume fraction would lead to larger compression plasticity. The interparticle spacing as well as the confinement zone size appears to be an effective factor in affecting the plasticity of BMGCs.

A novel Ni-free (Zr 48 Cu 32 Al 8 Ag 8 ,Ta 4 )Si 0.75 bulk metallic glass composite (BMG-C), showing an excellent combination of high strength and remarkable ductility, was laser spot welded with the pre-selected laser welding parameters. After welding, the microstructure evolution, glass forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vickers microhardness test. Test results showed that the parent material (PM), heat affected zone (HAZ) and weld fusion zone (WFZ) in the welds all consist of an amorphous matrix with two kinds of Ta particles: micro-sized and nano-sized. In the WFZ, during the rapid melting, the partial dissolution of micro-sized Ta particles resulted in the reduction of their volume fraction. After subsequent rapid cooling, partial micro-sized Ta particles were transformed to nano-sized particles or nano-sized particle accumulations. This transformation resulted in a slightly higher magnitude of hardness in the WFZ. Furthermore, it was found that the surrounding area of micro-sized Ta in the WFZ has better resistance to the etchant solution. In the HAZ, small amounts of Zr 2 Cu and nano-sized Ta tended to precipitate on the micro-sized Ta surface, and may act as heterogeneous nucleation sites. However, the small amount of precipitation in the HAZ and the micro-sized Ta transformation in the WFZ did not significantly affect the magnitude of the GFA indices, Δ T x , γ and γ m , when compared to that of un-welded BMG-C.

In this paper, we reported the thermoplastic deformation and micro/nano forming ability of a Au 49 Ag 5.5 Pd 2.3 Cu 26.9 Si 16.3 bulk metallic glass (BMG) in the supercooled liquid region (SCLR) at strain rates ranging from 1×10 –4 to 3×10 –2 s −1 . It is found that the deformation behavior of Au-based BMG has strong dependences on strain rate and temperature applied. The strain-rate sensitivity value, obtained by the strain-rate change method, approaches an unity (Newtonian flow) at low strain rates of 10 –4 s −1 , but it decreases with increasing strain rate to ∼0.3 (non-Newtonian flow) at 10 –2 s −1 . The homogeneous flow behavior is observed from the compressive test results. As the result of homogeneous flow, the deformability with a high compressive strain of ∼97% is achieved. The excellent micro/nano-patterning obtained at 430 K is also demonstrated for imprinted stripes with a feature size of ∼156 nm, signifying the good formability of this alloy in SCLR.

A continuous near-field electrospinning (NFES) process has been demonstrated to be able to achieve direct-write and well-aligned chitosan/poly(ethylene oxide) nanofibers. The ability to precisely control and deposit chitosan-based nanofibers in a direct-write manner is favorable in manipulating cells attachment and proliferation at a preferred position. Experimental results show that fiber diameters can be reliably controlled in the range of 265–1255 nm by adjusting various operating parameters of the NFES processes. These prescribed patterns of nanofibers exceed tens of centimeters long and complex configurations such as grid arrays and arc shapes are assembled at specified separations as small as 5 μm. FTIR analysis reveals that NFES nanofibers have a similar morphology and composition as conventional electrospinning counterpart and constitute all components formerly present in the polymer solution. The versatile functionality to fabricate chitosan-based nanofibers with controllable size and directional...