Work Functions of Pd_(83.5)Si_(16.5)and Cu_(70)Ti_(30)Glassy Alloys

The work functions before and aftercrystallization of two glassy alloys,Pd_(83.5)Si_(16.5) andCu_(70)Ti_(30) have been measured by means of the con-tact potential difference method in the secondaryelectron field at room temperature under 10~(-5) Pavacuum.The results show that the work functionsof both glassy alloys are higher than those of thecorresponding crystalline alloys.     

Structure and thermal stability of vapour-deposited Fe-Cu alloys

The structure of vapour-deposited Fe-Cu alloys was analysed and compared with that obtained by quenching from the liquid and solid state. Transmission electron microscopy was used to observe grain size at room temperature and precipitation at elevated temperatures. A discussion of thermal stability of metastable phases is based on nucleation mechanisms and diffusion coefficients in the highly defect or glassy state and the crystalline state.     

Synthesis and electrical conductivity of crystalline and glassy alloys in the Ag3GeS3Br-GeS2 system

We have studied the formation of crystalline and glassy alloys in the Ag₃GeS₃Br-GeS₂ system (0–52 mol % GeS₂; Ag₃GeS₃Br is a glass-forming phase of variable composition) and determined the crystallographic parameters of the Ag_3.179(9)Ge_1.474(5)S₄Br alloy as the saturated solid solution of GeS₂ in Ag₃GeS₃Br: sp. gr. P2₁3, a = 10.16572(3) Å, Z = 4. The electrical conductivity of the crystalline and glassy alloys was measured in the temperature range 250–410 K by a dc probe technique. The current carriers in the alloys are silver cations and halogen anions. We obtained materials with superionic conductivity and proposed a model for conduction in the alloys.     

An Overview of Hydrogen Interaction with Amorphous Alloys

Theories, experimental results and applications associated with hydrogen behavior in amorphous metals and alloys are reviewed. An emphasis is made on the potential use of these advanced materials for hydrogen storage technology. Therefore, several properties that are especially relevant for such applications are assessed. These include structural models for hydrogen occupancy, sorption characteristics, solubility, diffusion behavior and thermal stabilities. Hydrogen effects on the mechanical properties and fracture modes of glassy metals are also presented, and possible mechanisms of hydrogen embrittlement are discussed. Similarities and differences between hydrogen behavior in amorphous and crystalline metals and alloys are discussed in detail.     

Nanostructured Composite Materials with Improved Deformation Behavior

The recent progress in the development of nanostructured composites is described for Zr‐base multicomponent alloys as a typical example for such materials. These advanced composite materials are attractive candidates for structural as well as functional applications. The combination of high strength with high elastic strain of fully nanocrystalline and glassy alloys renders them quite unique in comparison to conventional (micro‐)crystalline materials. However, one major drawback for their use in engineering applications is the often limited macroscopic plastic deformability, despite the fact that some of these alloys show perfectly elastic‐plastic deformation behavior. To improve the room temperature ductility of either fully nanocrystalline or amorphous alloys, the concept of developing a heterogeneous microstructure combining a glassy or nanostructured matrix with second‐phase particles with a different length‐scale, has recently been employed. This review describes the composition dependent metastable phase formation in the Zr‐(Ti/Nb)‐Cu‐Ni‐Al alloy system, which in turn alters the mechanical properties of the alloys. We emphasize the possibilities to manipulate such composite microstructures in favor of either strength or ductility, or a combination of both, and also discuss the acquired ability to synthesize such in‐situ high‐strength composite microstructures in bulk form through inexpensive processing routes.     

Phase formation in thin solid films subjected to fast charged particle bombardment

Crystalline or amorphous phase formation in ion bombarded binary alloys is explained in the framework of an atomistic approach based on the evolution of collision cascades in the target. The non-equilibrium compositional profile which results at the cascade-lattice interface, as a consequence of preferential segregation of one alloy component, relaxes to (meta)stable equilibrium via local interatomic interactions, simulated by charge transfer events. The products of such reactions are small clusters of an effective alloy, with atomic dimensions. Comparing surface and thermochemical properties of initial and effective alloys, it is possible to define a set of conditions to achieve glassy or crystalline products upon ion bombardment.     

Cobalt-based bulk glassy alloy with ultrahigh strength and soft magnetic properties

Bulk metallic glasses--formed by supercooling the liquid state of certain metallic alloys--have potentially superior mechanical properties to crystalline materials. Here, we report a Co(43)Fe(20)Ta(5.5)B(31.5) glassy alloy exhibiting ultrahigh fracture strength of 5,185 MPa, high Young's modulus of 268 GPa, high specific strength of 6.0 x 10(5) Nm kg(-1) and high specific Young's modulus of 31 x 10(6) Nm kg(-1). The strength, specific strength and specific Young's modulus are higher than previous values reported for any bulk crystalline or glassy alloys. Excellent formability is manifested by large tensile elongation of 1,400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultrahigh-strength alloy also exhibited soft magnetic properties with extremely high permeability of 550,000. This alloy is promising as a new ultrahigh-strength material with good deformability and soft magnetic properties.     

Bulk Glassy Alloys: Historical Development and Current Research

This paper reviews the development of current research in bulk glassy alloys by focusing on the trigger point for the synthesis of the first bulk glassy alloys by the conventional mold casting method. This review covers the background, discovery, characteristics, and applications of bulk glassy alloys, as well as recent topics regarding them. Applications of bulk glassy alloys have been expanding, particularly for Fe-based bulk glassy alloys, due to their unique properties, high glass-forming ability, and low cost. In the near future, the engineering importance of bulk glassy alloys is expected to increase steadily, and continuous interest in these novel metallic materials for basic science research is anticipated.     

Effect of Nb addition on the subsurface deformation behavior in Cu47Ti34Zr11Ni8 bulk metallic glasses through Vickers indentation

In this paper, 3 mm diameter (Cu₄₇Ti₃₄Zr₁₁Ni₈)_100−xNb_x (x = 0,1,2) glass forming alloys were fabricated by water-cooled copper mould cast. Microstructural characterization reveals that the monolithic Cu₄₇Ti₃₄Zr₁₁Ni₈ bulk metallic glass exhibits homogenous amorphous structure. While the alloys with Nb addition exhibit a composite structure. For alloys with x = 1, micro-scaled crystalline particles were found to distribute in the glassy matrix. For alloys with x = 2, the microstructure is dominated by a high density of dendritic phase embedded in the glassy matrix. Bonded interface technique was adopted to study the deformation behavior of the alloys underneath the Vickers indentation. It reveals that the subsurface shear patterns are significantly affected by the precipitated phases. The different deformation mechanism of the alloys resulted from the minor Nb addition was put forward and discussed.     

Devitrification of Zr-Ni-Al-Cu-Ti(Nb,Ta) glassy alloys

The devitrification behavior and phase formation in Zr_65-55Ni₁₀Al_7.5Cu_7.5Ti_5-10(Nb,Ta)_5-10 metallic glass have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. It has been found that mutual addition of Ti and Ta/Nb benefits the formation of nanoscale icosahedral phase in the glassy phase on heating and the oxygen content in the alloy makes significant influence on the devitrification behavior of these alloys. At the same time in Nb-bearing alloys and alloys containing 5 at.% Ta icosahedral phase was found to coexist with crystalline one.     

Investigation of mechanical properties and devitrification of Cu-based bulk glass formers alloyed with noble metals

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu₅₅Zr₃₀Ti₁₀Pd₅ and Cu₅₅Zr₃₀Ti₁₀Ag₅ alloys while Cu₅₅Zr₃₀Ti₁₀Au₅ bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu₅₅Zr₃₀Ti₁₀Pt₅ bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu₆₀Zr₃₀Ti₁₀ glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young's modulus. A nanoicosahedral phase is primarily formed in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu₅₅Zr₃₀Ti₁₀(Ag,Pt)₅ alloys.     

Studies of ceramic-liquid metal reaction interfaces

An investigation has been made of the nature and extent of chemical reactions between various liquid metals and a range of engineering-grade ceramics typically used as cutting tool inserts. Such possible reactions are relevant to chemical wear effects during metal cutting but also relate to liquid metal containment by ceramics and ceramic-metal joining. The experimental procedure has involved immersing pre-polished ceramic sections in liquid metals for controlled times with subsequent sectioning and examination of the reaction interface. The ceramics studied were two alumina-based materials and five silicon nitrides and sialons. The metals were pure iron, pure nickel and four iron-nickel alloys (a mild steel, a stainless steel and two nickel-based superalloys) and span a range of Fe-Ni compositions. The reaction rates of the alumina materials were found to be much lower than those of the silicon nitride-based materials and reflect the chemical stability of the Al-O bond array. Zirconia-toughened alumina showed little evidence of reaction with clean iron alloys but substantial attack by oxygen-containing iron-based materials was found resulting in the formation of iron-aluminium spinel reaction products. Al₂O₃-TiC/N exhibited preferential metal attack of the carbonitride phase with dissolution and/or replacement of the TiC/N dispersion. Within the silicon nitride-based group, ferrous alloys were found to be more damaging than mainly nickel alloys and silicon nitrides were more readily attacked than sialons. The difference in behaviour between the sialons and silicon nitrides is attributed to alumina additions in the former group of materials increasing resistance to attack by molten metals. A detailed mechanism of attack for these mixed-phase ceramics is proposed whereby a silicon concentration gradient is established from the crystalline ceramic phases, through the glassy binding phase, to the metal. The result is dissolution of the crystalline phase and an increase in volume fraction of the glassy binder at the metal-ceramic interface with concomitant progressive disruption of the ceramic microstructure.     

Investigation of mechanical properties and devitrification of Cu-based bulk glass formers alloyed with noble metals

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu₅₅Zr₃₀Ti₁₀Pd₅ and Cu₅₅Zr₃₀Ti₁₀Ag₅ alloys while Cu₅₅Zr₃₀Ti₁₀Au₅ bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu₅₅Zr₃₀Ti₁₀Pt₅ bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu₆₀Zr₃₀Ti₁₀ glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young’s modulus. A nanoicosahedral phase is primarily formed in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu₅₅Zr₃₀Ti₁₀(Ag,Pt)₅ alloys.     

金属间化合物与大块玻璃合金的形成

综述了大块玻璃合金液态结构,结晶动力学行为,玻璃态形成机制以及其与金属间化合的关系,应用二元合金液态结构的理论模型,分析与推测,分析与推测大块玻璃合金的液相结构,解释了大块玻璃合金的特殊热力学性质和大块玻璃态形成机制,介绍了Ｚｒ基大块玻璃合金的一些研究结果。     

Synthesis of amorphous niobium-nickel alloys by vapor quenching

Thin film samples (10–15 μm thick) of niobium-nickel alloys in the composition range Nb-5 to 95 at. % Ni were vapor quenched bu r.f. sputtering onto fused quartz substrates held at a temperature of 180°C. It was found that fully glassy alloys were synthesized in the composition range Nb-30 to 85 at. % Ni, which is 2.5 times larger than that reported for splat-quenched alloys. Crystallization temperatures exhibited a maximum near the deepest eutectic in this alloys system and are comparable with those of splat-quenched materials. Nearest neighbor distances are in agreement with results for splat-quenched materials while “effective particle sizes” are consistently smaller. These results are discussed relative to the mechanism by which glassy alloys are synthesized during vapor quenching and the structure of the glassy state.     

大块非晶形成合金液体的热物理性能与玻璃形成能力

大块非晶合金由于其优异的性能而成的具有很大潜力的新材料，而合金的玻璃形成能力（GFA）的大小是能否获得大块非晶合金的根本所在。因此研究合金的玻璃形成能力成为材料科学领域重要的研究课题。本文从液体热物理性能出发，结合在这些方面所做的研究工作对大块非晶形成合金液体的玻璃形成能力做了一些探讨，希望对大块非晶合的研究有所裨益。     

Influence of Small Cr Addition on Thermal Stability and Magnetic Properties of Fe-Co-Zr-Nb-B Glassy Alloys

Fe62Cos-xCrxZr6Nb4B20 （x=0-4 at. pct） metallic glasses show high thermal stability with a maximum supercooled liquid region of about 84.8 K. The addition of 2 at. pct Cr causes the extension of the supercooled liquid region remarkably, leading to the enhancement of thermal stability and glass-forming ability. The crystallization of the Fe-based glassy alloys takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The long-range atomic rearrangements required for the precipitation of the multiple crystalline phases seem to play an important role in the appearance of the large supercooled liquid region through the retardation of the crystallization reactions. The Fe-based alloys exhibit soft ferromagnetic properties. The saturation magnetization decreases with increasing Cr content while the saturated magnetostriction increases as a function of Cr content. There is no distinct change in the saturation magnetization and coercive force with annealing temperature below the crystallization temperature. The devitrification gives rise to a considerable enhancement in both as and He.     

Crystallization and Corrosion Resistance of (Fe0.78Si0.09B0.13)100-xNix （x=0,2 and 5） Glassy Alloys

The crystallization of the (Fe0.78Si_0.09B0.13)100-xNix glassy alloys （x=0, 2 and 5） has been investigated by X-ray diffraction （XRD） and differential scanning calorimeter （DSC）. Corrosion resistance analyses have been carried out using electrochemical measurements and corrosion products have been analyzed by scanning electron microscopy （SEM）. The experimental results show that the addition of Ni can promote the nucleation of α-Fe, retard the decomposition of the metastable borides, and alter the crystallization mode of the present Fe-based glassy alloys. The lattice constant （a0Fe） of α-Fe in the annealed samples shows a decreasing trend with increasing annealing time. The Ni addition can improve the corrosion resistance of the as-quenched Fe-based glassy alloys in H2SO4, NaCl and NaOH solutions. The results indicate that Ni can promote the diffusion of Si atoms during quenching and annealing processes.     

Cu基块体非晶合金的研究进展

综述了国内外最近几年来Cu基大块非晶合金的研究现状,介绍了Cu基大块非晶合金在玻璃形成能力、机械性能、耐腐蚀性能、非晶-纳米晶合金方面的研究成果,最后探讨了Cu基大块非晶合金未来的研究重点.     

Surface nucleated crystallization in Ge15Te80As5 semiconducting glasses

The crystalline morphology of electrically conductive surface layers in thermally annealed bulk samples of Ge₁₅Te₈₀As₅ glass has been studied using a scanning electron microscope. Results confirm previous suggestions that crystallization is surface nucleated. Two regions of different crystalline morphology are observed and result from a two-stage crystallization process. Selected-area electron diffraction on extracted particles was used to identify the crystalline phases. The crystallites near the inner glassy material are Te, the first phase to segregate upon annealing. The crystalline material near the sample surface is more dense and contains two phases: GeTe (second-stage crystallization product) and crystalline Te. Energy Dispersive X-Ray Analysis with spacial resolution of 2–3 μm and accuracy of ±10% has shown that the “average” composition is the same for these crystalline regions and for the glassy material.