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Abstract: Dry sliding wear behaviors of a series of bulk metallic glasses with nominal compositions of Zr48Cu45−x Al7Ag x (x =0, 2, 5, 8at.%) are investigated by pin-on-disk method at room temperature. Compared with Ag-free Zr48Cu45Al7 glassy alloy, wear resistances of the Ag-doped bulk metallic glasses are significantly enhanced and increased with the content of Ag, and their microhardnesses also increase. The results of compression test show that the plastic strain decreases with the increase of Ag content for the quaternary Zr–Cu–Al–Ag alloys. SEM observations demonstrate that the cracks initiate and propagate perpendicular to the frictional direction during the debris formation. [Copyright &y& Elsevier]

Abstract: Thermal stability and crystallization kinetics of an as-prepared Cu35Ag15Zr45Al15 metallic glass have been investigated by differential scanning calorimeter and X-ray diffraction. It is found that Cu35Ag15Zr45Al15 has a supercooled liquid region as large as 114K at a heating rate of 40K/min. Crystallization kinetic studies show that glass transition as well as crystallization behave in a typical kinetic nature with Kauzmann temperature T k about 610K and activation energies of E g =483±75kJ/mol and E x =253±8kJ/mol for glass transition and crystallization, respectively. The addition of Ag in the Cu–Zr–Al alloy system might improve the packing efficiency and increase the complexity of the system. Consequently, an excellent thermal stability is achieved for the Cu35Ag15Zr45Al5 metallic glass. [Copyright &y& Elsevier]

Abstract: We report composition optimization, thermal and physical properties of new La-based bulk metallic glasses with high glass forming ability (GFA) based on a ternary La62Al14Cu24 alloy. By refining the (Cu,Ag)/(Ni,Co) and La/(Cu,Ag) ratios in the La–Al–(Cu,Ag)–(Ni,Co) pseudo-quaternary alloy, the formation of 30mm diameter of La65Al14(Cu5/6Ag1/6)11(Ni1/2Co1/2)10 bulk metallic glass (BMG) alloy is achieved using water quenching. The origin of the high GFA was investigated from the kinetic, structural and thermodynamic points of view, and was found to be due to the smaller difference in Gibbs free-energy between the amorphous and crystalline phases in the pseudo-quaternary alloy. These alloys exhibit low glass transition temperatures, below 430K, and relatively wide supercooled liquid regions of 40–60K. Mechanical tests on these alloys show a fracture strength of 650GPa, Vicker’s hardness 200kgmm−2, Young’s modulus 35GPa, shear modulus 13GPa and Poisson ratio 0.356. The La-based BMGs are useful for both scientific and engineering applications. [Copyright &y& Elsevier]

Abstract: Glass forming ability, thermal and mechanical properties of (La0.5Ce0.5)64Al16Ni5Cu15−x Co x (x =0, 3, 5, 8 and 10at.%) bulk metallic glasses were investigated. Fully amorphous 1.2cm rods of the (La0.5Ce0.5)64Al16Ni5Cu10Co5 alloy and 1.0cm rods of (La0.5Ce0.5)64Al16Ni5Cu15−x Co x (x =0, 3, 5, 8 and 10at.%) alloys are obtained. The (La0.5Ce0.5)64Al16Ni5Cu10Co5 alloy exhibits higher glass forming ability, lower glass transition temperature of 413K, wider supercooled liquid region of 54K, hardness and fracture strength of 2GPa and 530 MPa, respectively, which could become potential micro- and nano-imprintable materials. [Copyright &y& Elsevier]

Abstract: The Ni-based ternary bulk metallic glasses (BMGs) with critical diameter up to 3mm were discovered in Ni–Nb–Zr system using a strategy for catching the best glass former based on relative glass forming ability of alloys. The best glass former Ni62Nb33Zr5 exhibits glass transition temperature of 877K, supercooled liquid region of 40K, compressive strength of about 3GPa, plastic strain of about 1%. [Copyright &y& Elsevier]

Abstract: We report a series of bulk metallic glass-forming alloys of compositions (Cu45Zr48−x Al7RE x , RE=La, Ce, Nd, Gd and 0≤ x ≤5at.%). By using a conventional copper mold sucking method, alloys with diameters ranging from 5 to 10mm can be readily solidified into an amorphous structure without detectable crystallites. The best glass-forming ability is obtained for the alloys Cu45Zr46Al7RE2. Possible effects of RE addition on the glass-forming ability are discussed. In addition, the compositional effect on mechanical properties of Zr–Cu–Al–Gd alloys is presented. [Copyright &y& Elsevier]

Abstract: LaCe-based bulk metallic glasses (BMGs) with diameter up to 10mm have been synthesized in copper mold. The BMG alloys have low glass transition temperatures, about 403K and large supercooled liquid regions up to 58K. The hardness of the BMG alloys is around 1.9GPa. They also exhibit large plasticity and imprintability feature in the supercooled liquid region, which make the alloy a potential imprinting material. In addition, the BMG alloys might offer an ideal model system for the study of glass transition with a large experimentally accessible time and low temperature windows. [Copyright &y& Elsevier]

A bimodal size metallic glassy particles reinforced 7075 aluminum composite was fabricated by powder metallurgy via ball milling and hot extrusion. The results show that metallic glassy reinforcements help to improve the densification due to the liquid-like behavior in the supercooled liquid region. The metallic glassy reinforcements were found to have a bimodal size distribution at nanoscale and microscale, and were uniformly distributed in the matrix. An interphase layer with a thickness of 60–80 nm was observed between the reinforcement/matrix resulted from elemental diffusion and chemical reaction. The introduction of bimodal size metallic glassy particles have significantly improved the mechanical properties, where the yield strength and fracture strength increase from 442 and 648 MPa for Al7075 to 869 and 962 MPa for composite with 17 vol% reinforcement, respectively. The strengthening mechanisms of the composites were revealed. • Al alloy matrix composites with bimodal-sized metallic glassy reinforcement were produced. • Metallic glassy reinforcements help to improve the densification. • An interphase layer formed due to the elemental diffusion and chemical reaction. • The composites provide a reasonable combination of strength and ductility. [ABSTRACT FROM AUTHOR]

The limited plasticity of bulk metallic glasses (BMGs) is commonly circumvented by introducing micrometer- or nanometer-sized heterogeneities (crystallites and/or phase separation) into the BMGs. In this work, we report the improvement of plasticity in a ternary monolithic BMG caused by a large amount of randomly distributed free volume induced during solidification using a high cooling rate. This indicates that introducing large amounts of free volume into BMGs might be another promising way of improving the plasticity of these materials. [Copyright &y& Elsevier]

Abstract: In this paper, we report the formation of a series Zr–(Cu,Ag)–Al bulk metallic glasses (BMGs) with diameters at least 20mm and demonstrate the formation of about 25g amorphous metallic ingots in a wide Zr–(Cu,Ag)–Al composition range using a conventional arc-melting machine. The origin of high glass-forming ability (GFA) of the Zr–(Cu,Ag)–Al alloy system has been investigated from the structural, thermodynamic and kinetic points of view. The high GFA of the Zr–(Cu,Ag)–Al system is attributed to denser local atomic packing and the smaller difference in Gibbs free energy between amorphous and crystalline phases. The thermal, mechanical and corrosion properties, as well as elastic constants for the newly developed Zr–(Cu,Ag)–Al BMGs, are also presented. These newly developed Ni-free Zr–(Cu,Ag)–Al BMGs exhibit excellent combined properties: strong GFA, high strength, high compressive plasticity, cheap and non-toxic raw materials and biocompatible property, as compared with other BMGs, leading to their potential industrial applications. [Copyright &y& Elsevier]

Abstract: Materials may be strong or ductile, but rarely both at once. However, the combination of high strength and good ductility is significant for application of materials as structural materials. In this work, we report a Ni–Nb alloy, which exhibits ultrahigh compressive strength of up to 3500MPa together with good compressive ductility of 5.3%. To the best of our knowledge, the plastic strain is larger than previous values reported for any bulk ultrahigh strength (over 3000MPa) alloys. The good ductility is due to the heterogeneous microstructure of the alloy. [Copyright &y& Elsevier]

Abstract: Microstructure and crystallization of a Cu50Zr45Al5 metallic glass have been investigated by differential scanning calorimetry, X-ray diffraction and extended X-ray absorption fine structure (EXAFS) using synchrotron radiation. The width of the supercooled region is ΔT x = T x − T g =67K, where T x and T g are the crystallization and the glass transition temperature, respectively; the reduced glass transition temperature is T rg = T g/T l =0.65, where T l is the liquid temperature; and γ = T x/(T g + T l)=0.41. After crystallization of the as-prepared Cu50Zr45Al5 metallic glass, crystalline phases are identified as tetragonal CuZr2 and orthorhombic Cu10Zr7. The local atomic structures deduced from EXAFS reveal that Zr atoms in the as-prepared Cu50Zr45Al5 metallic glass are surrounded by about 5 Cu atoms at a distance of 2.70Å and about 5 Zr atoms at 3.14Å. [Copyright &y& Elsevier]

The poor hot workability of aluminum matrix composites (AMCs) severely limits their engineering use. Here an abnormal hot deformability phenomenon was observed in a metallic glass-particle-reinforced AMC in which the composite shows higher strength at room temperature and lower strength at higher temperatures than the monolithic Al-7075 alloy, indicating excellent hot workability. It reveals that the metallic glass at high temperature may be as a soft binder to release the local stress concentration during deformation owing to drop in viscosity. This study provides new opportunities for designing and achieving good workability in AMCs for advanced structural applications. • An abnormal hot deformation behavior was observed in present composite. • The composite shows lower flow stress at elevated temperatures than the matrix. • Reconstructed 3D microstructure of the metallic glass-composite was built. • It reveals that the metallic glass at high temperature may be as a soft binder. [ABSTRACT FROM AUTHOR]