•Zr56.25Al18.75Co18.75Cu6.25 BMG exhibits large GFA, high strength and plasticity.•Split d-band affects the thermal and mechanical stabilities of ZrAlCoCu BMGs.•Zr56.25Al18.75Co18.75Cu6.25 BMG is a promising surgical devices material.Toxic element-free Zr-based bulk metallic glasses (BMGs) with a property combination of high glass-forming ability, ultrahigh strength and large room-temperature plasticity are useful as surgical devices materials. In the present work, the critical glass formation size (dmax), thermal glass stability and room-temperature mechanical properties of a series of Zr56.25Al18.75(Co1-xCux)25 (x = 0, 0.125, 0.25, 0.375, 0.5, at.%) alloys have been investigated. The Zr56.25Al18.75Co18.75Cu6.25 (x = 0.25) BMG alloy is found to combine a centimeter scale dmax with ultrahigh strength (σy = 2.05 GPa), high Young's modulus (E = 92.4 GPa) and large room-temperature plasticity (ɛP = 3.5%). Comparison of the property combination of various biomedical Zr-based BMGs suggests that the Zr56.25Al18.75Co18.75Cu6.25 BMG can be a promising surgical devices material. The thermal and mechanical stabilities of these BMG alloys are qualitatively understood with the electron concentration and split d-band electronic structure stabilization mechanisms.

A series of ternary rare-earth metal aluminum germanides with the general formula REAl1−xGe3 (RE = Nd, Sm, Gd, Tb, Dy, and Ho; 0.6 < x < 0.9) have been synthesized by direct fusion of the corresponding elements. Their structures have been characterized by single-crystal X-ray diffraction and selected area electron diffraction methods. The average structure for all members is a representative of the orthorhombic SmNiGe3-type structure (Pearson symbol oS20, space group Cmmm), where the Al atoms occupy the Ni site, and the deep off-stoichiometry is due to statistical vacancies at this position. Considering long-range ordering of the vacancies, a monoclinic and a different orthorhombic structure, which represent idealized ordered variants, are possible, and the structural evolution depending on the nature of the rare-earth metals and the amount of vacancies at the aluminum site are discussed. Commensurate and incommensurate structural modulations based on these parent structures are also observed by electron diffraction, attesting to the great structural complexity in these systems. Magnetic susceptibility measurements are presented and discussed, along with the results from electronic band-structure calculations.

The alloying effects of the like-atom substitution of Ni and Co for Fe on the various properties of Fe70B16.7Si8.3Ta5 metallic glass are investigated in this present work. New Fe-based bulk glassy alloys, namely Fe60–xCoxNi10B16.7Si8.3Ta5 (at.%; x = 10, 20 and 30) with critical diameters up to 1.5 mm, were made by means of copper mold casting. A new glass-forming ability indicator, viz., the enthalpy of supercooled liquid, has been introduced for assessment of the glass-forming abilities (GFAs) of these Fe-based multi-component alloys. Nano-indentation results indicate that the calculated elastic modulus and hardness of the bulk glassy alloys are lower than those of the Fe70B16.7Si8.3Ta5 alloy. Among these bulk glassy alloys, Fe70B16.7Si8.3Ta5 exhibits the large elastic modulus and hardness with values of 178 ± 1 GPa and 12.9 ± 0.1 GPa, respectively. All the bulk glassy alloys exhibit good soft magnetic properties with high saturation magnetization Bs ~ 0.75–1.04 T but low coercive force Hc ~ 0.2–5.2 A/m.

•The role of minor Sn alloying in improving glass formation in U-based system is revealed.•New U-based U-Fe-Sn metallic glasses are achieved.•The new glasses have high thermo-stability and glass-forming ability.•The glass composition tendency in U-Fe system is clarified.The effect of minor Sn alloying on the glass formation of U-based alloys is investigated. A string of U-Fe alloys designed with the eutectic rule are all formed in a partially glassy state under melt-spinning. Minor addition of Sn gives rise to the full amorphisation of the alloys, and the achievement of the reduced glass transition temperature for new U-Fe-Sn alloys comparable to some ordinary bulk metallic glasses. This role of Sn microalloying may be ascribed to improved packing efficiency of icosahedral atomic clusters underlying in the alloy liquids. It is suggested that local atomic packing is a necessary consideration for exploiting desirable U-based multicomponent alloys with high glass forming ability.

•A new metallic glass system based on uranium is achieved.•The glass-forming ability is the highest among U-based metallic glass systems.•The U-based glasses have good anti-corrosive and mechanical properties.•The deviation of elastic modulus from rule-of-mixture is revealed.A series of U-based U-Co-Al metallic glasses with greatly improved glass-forming ability and thermal stability were obtained by the alloying addition of Al into U-Co alloys. The fragility of these glasses approached 28, indicating strong liquid behavior. The corrosion resistance and mechanical hardness of the glasses were substantially enhanced in comparison with crystalline uranium materials. The roles of delocalization of 5f electrons and their bonding states are stressed in the discussion of the glass formation, thermal stability and the deviation of elastic modulus from the rule of mixtures. The finding not only adds a new member to the family of metallic glasses, but also provides a category of potentially useful uranium materials.

The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3, where NiFe12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni) with surplus Ni was then determined to ensure the second phase (Ni3M) precipitation, based on which new multi-component alloys [(Ni,Cu)16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V)16) were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu4Ni12)Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1)) alloy (Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78 wt%) has higher tensile strengths with YS=1456 MPa and UTS=1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.

In the present work we have studied the formation of bulk metallic glass in the Zr–Co–Al system. Using the atomic-cluster-plus-glue-atom model, a cluster formula composition, [Co2Al2Zr7](Co2Zr) = Zr57.1Co28.6Al14.3), was derived to explore bulk metallic glass formation. Glass rod of 10 mm diameter can be made at this composition by copper mold casting. The glass alloy exhibited an undercooled liquid span of 43 K at a constant differential calorimetric heating rate of 40 K/min. Under uniaxial compression at room temperature, the alloy exhibited a yield strength of 2,100 MPa and a plastic strain of 10 %.

The crystallization of (Zr65Al10Ni10Cu15)98Nb2 metallic glasses has been studied using transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The ribbon glass and bulk metallic glass (BMG) of this alloy exhibit different crystallization behaviors. For ribbon glass in the first stage crystallization, icosahedral quasicrystal (I-phase) precipitated together with the η-Zr2Ni (a = 1.226 nm) phase. The BMG alloy transforms into the I-phase and two coherently coexisted phases, namely, the Al2Zr3 phase and an unknown primitive cubic phase (a = 0.76 nm) in this stage. The experimental evidence indicates that the liquid cooling rate for sample preparation has a significant effect on its crystallization behavior of this alloy glass.

•A Ti-Fe-Sn thin film assembly was designed for brazing W and reduced activation ferritic/martensitic steels.•W/steel joints free of pores and cracks were obtained by vacuum brazing at 1090 °C.•The W/steel joints demonstrated high strength and high thermocycling stability.•The presence of Sn in the brazed joints depressed the formation of defects and resulted in microstructure refinement.The effective joining of tungsten and reduced activation ferritic-martensitic (RAFM) steels is crucial to fabrication of the divertor components of fusion reactors. In the present work, a low neutron-activation filler metal system of Ti-Fe-Sn was designed to realize the so-called exothermic-reaction-assisted brazing. A series of three-layered Ti-Fe-Sn thin film assemblies were made by electroplating, which allowed the brazing of tungsten with a CLF-1 RAFM steel to be carried out at a temperature as low as 1090 °C. The joint structures made from the Sn-bearing filler metals demonstrated high strength and high resistance against thermocycling. The Sn-film layer in the filler assembly has delivered favorable alloying effects on depressing separation of Ti element in the W grain boundaries and the formation of pores, and on microstructure refinement in the brazed joints as well.Download high-res image (197KB)Download full-size image

A series of ternary rare-earth metal aluminum germanides with the general formula REAl1−xGe3 (RE = Nd, Sm, Gd, Tb, Dy, and Ho; 0.6 < x < 0.9) have been synthesized by direct fusion of the corresponding elements. Their structures have been characterized by single-crystal X-ray diffraction and selected area electron diffraction methods. The average structure for all members is a representative of the orthorhombic SmNiGe3-type structure (Pearson symbol oS20, space group Cmmm), where the Al atoms occupy the Ni site, and the deep off-stoichiometry is due to statistical vacancies at this position. Considering long-range ordering of the vacancies, a monoclinic and a different orthorhombic structure, which represent idealized ordered variants, are possible, and the structural evolution depending on the nature of the rare-earth metals and the amount of vacancies at the aluminum site are discussed. Commensurate and incommensurate structural modulations based on these parent structures are also observed by electron diffraction, attesting to the great structural complexity in these systems. Magnetic susceptibility measurements are presented and discussed, along with the results from electronic band-structure calculations.