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Abstract: We have successfully synthesized the porous Mo particles reinforced Mg58Cu28.5Gd11Ag2.5 metallic glass composites (BMGCs) rods with a diameter of 2∼6mm by injection casting in an Ar atmosphere. The glass forming ability and mechanical properties of such Mg-based BMGCs are systematically investigated as a function of porous Mo volume fraction and injection-cast cooling rate. The results show that superior mechanical performance with up to 14% compressive failure strain, 1050MPa yield strength and 1200MPa fracture strength at room temperature can be obtained for the Mg-based BMGC with 25vol% Mo particles. The dispersed porous Mo particles act as a network in the amorphous matrix, which restricts the highly localized shear banding into many isolated micro-scaled regions, avoiding complete shear-through of one principal shear band across the whole sample. This results in the formation of multiple shear bands within or around the porous Mo particles and the decrease of stress concentration for further propagation of shear band, enhancing the plasticity. Moreover, the yield strength and plastic strain exhibit an increasing trend with increasing cast cooling rate, due to lower residual porosity. [Copyright &y& Elsevier]

Abstract: The amorphous alloy rods of (Zr53Cu30Ni9Al8)100−x Six (x =0.25, 0.5, 0.75, 1) with a diameter of 2–6mm were prepared by drop casting method in an Ar atmosphere. The thermal properties, including glass forming ability (GFA) and thermal stability during isothermal annealing of these amorphous alloys, and the mechanical properties have been systematic investigated by the combination of DSC, XRD, SEM, TEM, and compression test. The result of X-ray diffraction reveals that these entire (Zr53Cu30Ni9Al8)100−x Si x alloy rods exhibit a typical amorphous diffraction pattern with only a broad maximum around 2θ around 40 degree. Both T g (glass transition temperature) and T x (crystallization temperature) of these (Zr53Cu30Ni9Al8)100−x Si x alloys increase with the silicon addition. In addition, both the activation energy of crystallization and the incubation time of isothermal annealing these (Zr53Cu30Ni9Al8)100−x Si x amorphous alloys indicate that the (Zr53Cu30Ni9Al8)99.25Si0.75 alloy possesses the best thermal stability in the (Zr53Cu30Ni9Al8)100−x Si x alloy system. In parallel, the result of compression test shows that the yield strength increases with the addition of Si content and reaches to a maximum value about 1750MPa with 3% plastic strain for the (Zr53Cu30Ni9Al8)99.25Si0.75 amorphous alloy. [Copyright &y& Elsevier]

Abstract: The thermal plastic deformation behavior of the (Zr53Cu30Ni9Al8)99.5Si0.5 bulk metallic glass (BMG) was studied by means of thermo mechanical analysis (TMA) and high-temperature compression test in the supercooled liquid region. Using the result obtained from TMA, the deformation behavior for (Zr53Cu30Ni9Al8)99.5Si0.5 BMG rod was investigated by compression test at different strain rates (5×10−3∼5×10−1 s−1) and temperatures in the supercooled liquid region, specifically at 733K, 738K, 743K, 748K, and 753K. The value of flow stress with a constant strain rate of 5×10−3 s−1 decreases with increasing temperature and reaches a relatively low flow stress of 36MPa at the test temperature of 753K. Conversely, the value of flow stress increases with the strain rate in compression. In this paper, an imprinted hologram pattern with 0.6μm depth was demonstrated which showed extremely good microforming ability of this (Zr53Cu30Ni9Al8)99.5Si0.5 BMG in the supercooled liquid region. [Copyright &y& Elsevier]

The effect of small additions of boron and carbon on the environment embrittlement at different temperature of Ni–19Si–3Nb based alloy was investigated by atmosphere-controlled tensile test in various conditions. The results revealed that the Ni–19Si–3Nb base alloy exhibits ductile mechanical behavior (UTS∼1250 MPa, #x03B5;∼14%) at room temperature in vacuum (2×10-4 torr) as well as in pure oxygen atmosphere. This indicates that environmental embrittlement due to water vapor is the major factor to the deterioration of the ductility of Ni–19Si–3Nb base alloy. In parallel, 300 ppm boron addition significantly improves the ultimate tensile strength and the ductility (UTS≥1200 MPa, #x03B5;≥12%) in the Ni–19Si–3Nb base alloy at room temperature in various atmosphere of pure oxygen, air (contains 14000 ppm water vapor), and pure water vapor (contains 850 ppm water vapor). In addition, the yield strength of the Ni–19Si–3Nb–0.15B–0.1C alloy increases with temperature, and the maximum yield strength occurs at 873 K. However, the ductility of the Ni–19Si–3Nb–0.15B–0.1C alloy drops significantly when the temperature increases to 973 K. [Copyright &y& Elsevier]

The Ni–19Si–3Nb base alloy was microalloyed with different combinations of boron and carbon for modifying its precipitate microstructure as well as improving its ductility. The microstructural evolution in the Ni–19Si–3Nb–xB–yC alloys was characterized by X-ray diffraction, DTA, SEM, Auger analysis, and TEM. The results of X-ray diffraction and DTA could not reveal any phase change in the Ni–19Si–3Nb based alloys with different carbon and boron contents. However, the morphology of the Nb-rich precipitate (which was confirmed to be a cubic Nb3Ni2Si phase by selected area diffraction of TEM) changes from plate-like shape to discrete equiaxial shape when the boron and carbon additions increase to 100 ppm or more. Meanwhile, the fracture behavior of the Ni–19Si–3Nb alloy with different carbon and boron additions changes significantly from brittle mode to ductile mode. In addition, the results of Auger analysis revealed that the boron and carbon elements would segregate on the grain boundaries and the interface between Nb-rich precipitates and matrix. The additions of boron and carbon are suggested to improve the adhesion of grain boundaries to the matrix, and to re-modify the shape of the precipitates to resist crack propagation and improve the ductility of the Ni–19Si–3Nb-based alloy. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate, for the first time, that a thin, strong, ductile, and adhesive coating renders bulk metallic glasses (BMGs) bendable. The bending ductility of 3mm thick BMGs, Zr50Cu30Al10Ni10 in this case, can be dramatically enhanced from ∼0% to ∼13.7% by the deposition of a thin bilayer film on the tensile side of the BMG sample. The bilayer, consisting of a 25nm thick Ti adhesive layer with a 200nm thick metallic glass (MG) overlayer, exhibits the required synergistic combination of good adhesion, high strength, and ductility compared with other single-layer films examined (Ti, TiN, and MG). Cross-sectional scanning and transmission electron microscopy, together with finite element modeling, reveal that the bilayer coating absorbs deformation while allowing more homogeneous formation of a high density of smaller shear bands at the bilayer/BMG interface. The bilayer coating, in turn, covers surface weak points and minimizes the formation of localized shear bands which lead to catastrophic failure under bending. As a result, the average shear-band spacing in bilayer-coated BMGs is small, 54μm, and approximately equal to that found in bendable, 450μm thick, MG ribbons. Thus, coated BMGs can accommodate large strains and overcome the MG size effect, without sacrificing their extraordinary mechanical properties. Our results for both coated and uncoated BMGs, as well as previously reported results for uncoated metallic glasses, with thicknesses ranging from ribbons to thin plates to bulk, are well described by a simple power law relationship between plastic strain to failure and shear band spacing. This scaling law may be useful in guiding future experiments toward producing more flexible BMGs. [Copyright &y& Elsevier]

In this study, the various Sr(Ce 0.6 Zr 0.4) 0.9 Y 0.1 O 3-δ /YBaCo 2 O 5+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 H 2 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). • A composite high temperature proton ceramic membrane was prepared. • The electrical conductivity of samples is 13.44 S/cm at 800 °C. • A high hydrogen flux proton ceramic membrane was investigated. • A SCZY/YBCO film on the Ni-SCZY substrate was prepared and test for hydrogen permeation. [ABSTRACT FROM AUTHOR]

Abstract In this study, creep behavior of the face-centered-cubic (FCC) {111} and {100} grains in single-phase Fe 20 Co 20 Ni 20 Cr 20 Mn 20 and dual-phase Fe 18 Co 18 Ni 20 Cr 18 Mn 18 Al 8 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 Å3 or ∼12Ω, where Ω is the atomic volume) at 600 °C is larger than that reported for the Ni-based superalloys (∼50–100 Å3 or less) within a similar temperature range. The significance of this larger activation volume is also discussed. Graphical abstract Image 1 Highlights • Nanoindentation creep responses in high entropy alloys are examined over 300–600 °C. • The extracted activation energy under the constant stress condition is around 260 kJ/mol. • The current high entropy alloys possess relatively large volume about 140 Å3 at 600 °C. [ABSTRACT FROM AUTHOR]

The Ti x (AlCrVNb) 100-x (x = 20, 40, 60 and 80) low-density multi-principal element alloys (MPEAs) were prepared by vacuum arc-melting. The density, crystal structure, microstructure and mechanical properties of this new Ti x (AlCrVNb) 100-x are reported. The density of alloys decreases with increasing Ti content from 5.81 to 4.79 g/cm3. The microstructure of Ti20 consists of body-centered cubic (BCC) and minor amount of nano-sized particles segregating at grain boundaries, resulting in the brittleness of Ti20. But Ti40, Ti60 and Ti80 all consist of a single BCC solid solution phase. In addition, the experimentally observed phase constitutions are compared with the equilibrium and non-equilibrium thermodynamical modeling results. The compression yield strength decreases from 1122 MPa for Ti40 to 600 MPa for Ti80, due to the decreased atomic size difference. The combination of room-temperatured specific strength and ductility of Ti40 was found to be superior to most single-phase BCC MPEAs in the as-cast state. Promising room-temperature tensile properties were found for Ti60, better than those of most single-phase BCC MPEAs. The solid solution strengthening was found to be the dominant strengthening mechanism, making up more than 90% of the yield strength of Ti40–Ti80. Image 1 • A new light weight multi-principal element alloy TiAlCrVNb is successfully developed. • The phase evolution and mechanical response as a function of composition are explored. • The solid-solution hardening contributes more than 90% of the yield strength. [ABSTRACT FROM AUTHOR]