MICROSTRUCTURE AND MECHANICAL PROPERTIES OF TI-BASED METALLIC GLASS MATRIX COMPOSITES

Ti40Cu40Ni10Zr10-xScx (x = 0.5 and 1, at%) alloys were prepared by copper mould casting method. Microstructures of the phi 3 mm rod alloys were investigated by XRD and SEM. The results showed that the phi 3 mm rods were glassy matrix with TiCu crystalline phase. Mechanical properties were studied by compressive test. Ti40Cu40Ni10Zr9Sc1 alloy exhibited good compressive strength over 2200 MPa and superior compressive deformation is about 7.9%.

Crystallographic and electrochemical characteristics of melt-spun Ti-Zr-Ni-Cu alloys

Ti44Zr32Ni22Cu2 and Ti41Zr29Ni28Cu2 alloys were prepared by the melt-spinning method. The phase structure was analyzed by X-ray diffraction, and the electrochemical performances of the melt-spun alloys were investigated. The results indicated that the Ti44Zr32Ni22Cu2 alloy was composed of the icosahedral quasicrystals and amorphous phases, and the Ti41Zr29Ni28Cu2 alloy comprised icosahedral quasicrystals, amorphous, and Laves phases. The maximum discharge capacity was 141 mAh/g for the Ti44Zr32Ni22Cu2 alloy and 181 mAh/g for the Ti41Zr29Ni28Cu2 alloy, respectively. The Ti41Zr29Ni28Cu2 alloy also showed a better high-rate dischargeabifity and cycling stability. The better electrochemical properties should be ascribed to the high content of Ni, which was beneficial to the electrochemical kinetic properties and made the alloy more resistant to oxidation, as well as to the Laves phase in the Ti41Zr29Ni28Cu2 alloy, which could work as the electro-catalyst and the micro-current collector.

Highly efficient green phosphorescent organic light-emitting diodes based on Cu-I complexes

Mononuclear Cu-I complexes with mixed ligands are used to fabricate green phosphorescent organic light-emitting diodes. The electroluminescence (EL) maximum at 524 nm coincides well with its photoluminescent (PL) spectrum in poly(methyl methacrylate) film (see Figure). A maximum current efficiency of 10.5 cd A(-1) at 105 cd m(-2) and a maximum brightness up to 1663 cd m(-2) are

Highly efficient electroluminescence from green-light-emitting electrochemical cells based on Cu-I complexes

The complexes [Cu(dnpb)(DPEphos)](+)(X-) (dnpb and DPEphos are 2,9-di-n-butyl-1,10-phenanthroline and bis[2-(diphenyl-phosphino)phenyl]ether, respectively, and X- is BF4-, ClO4-, or PF6-) can form high quality films with photoluminescence quantum yields of up to 71 +/- 7%. Their electroluminescent properties are studied using the device-structure indium tin oxide (ITO)/complex/metal cathiode. The devices emit green light efficiently, with an emission maximum of 523 nm, and work in the mode of light-emitting electrochemical cells. The response time of the devices greatly depends on the driving voltage, the counterions, and the thickness of the complex film. After pre-biasing at 25 V for 40 s, the devices turn on instantly, with a turn-on voltage of ca. 2.9 V. A current efficiency of 56 cd A(-1) and an external quantum efficiency of 16% are realised with Al as the cathode. Using a low-work-function metal as the cathode can significantly enhance the brightness of the device almost without affecting the turn-on voltage and current efficiency. With a Ca cathode, a brightness of 150 cd m(-2) at 6 V and 4100 cd m(-2) at 25 V is demonstrated. The electroluminescent performance of these types of complexes is among the best so far for transition metal complexes with counterions.

Electrochemical characteristic of LaNi-based hydrogen storage alloys

Effect of purity of alloy components on the electrode performance of LaNi2 alloys was investigated. The results showed the purity of components had less effect on discharge capacity and self-discharge of LaNi2 alloys. Partial substitution of Al or Mn for Ni greatly improved discharge properties of LaNi2-xAlx, or LaNi2-yMny alloys as negative electrodes in MFl-Ni battery, 0.15less than or equal toxless than or equal to0.25; 0.15less than or equal toyless than or equal to0.25. In addition, surface treatment of LaNi1.8Al0.2 alloy electrode was performed by polymerizing cis-butenedioate with Co-60- gamma -ray radiation, which. had better affect on self-discharge and cycle life of the alloy electrodes at low temperature(-28 C-degrees).

Formation of Fivefold Deformation Twins in Nanocrystalline Face-Centered-Cubic Copper Based on Molecular Dynamics Simulations

Fivefold deformation twins were reported recently to be observed in the experiment of the nanocrystalline face-centered-cubic metals and alloys. However, they were not predicted previously based on the molecular dynamics (MD) simulations and the reason was thought to be a uniaxial tension considered in the simulations. In the present investigation, through introducing pretwins in grain regions, using the MD simulations, the authors predict out the fivefold deformation twins in the grain regions of the nanocrystal grain cell, which undergoes a uniaxial tension. It is shown in their simulation results that series of Shockley partial dislocations emitted from grain boundaries provide sequential twining mechanism, which results in fivefold deformation twins. (c) 2006 American Institute of Physics.

Microstructural features of an iron-based laser coating

A high toughness wear resistant coating is produced by laser clad Fe-Cr-W-Ni-C alloys. The microstructural and compositional features of the laser-solidified microstructures and phase evolutions occurring during high temperature tempering at 963 K were investigated by using analytical electron microscopy with energy dispersive X-ray analysis. The clad coating possesses the hypereutectic microstructure consisted of M7C3 + (Y + M7C3) Du ring high temperature aging, the precipitation of M23C6 and M2C in austenite and in situ transformation of dendritic M7C3 to M23C6 and eutectic M7C3 to M6C occurred. The laser clad coating reveals an evident secondary hardening and superior impact wear resistance.

Cu原子簇触发形核下的深过冷Ag-Ge合金组织演变研究

采用玻璃包覆的方法获得具有较大过冷度的亚共晶、共晶以及过共晶Ag-Ge合金熔体,并通过高能离子束轰击Cu箔产生Cu原子团簇溅射到过冷合金熔体中来触发非均质形核过程.凝固后合金显微组织的分析结果表明:在深过冷合金熔体中引入Cu原子团簇,它对亚共晶、共晶以及过共晶Ag-Ge合金的显微组织演变有着不同的影响效果,分析了显微组织的演变规律与形成机制. The Ag-Ge alloy melts with deeply undercooled hypoeutectic, eutectic and hypereutectic were obtained via glass fluxing technique. The nucleation of the deeply undercooled alloy melts were triggered by atoms cluster sputtering on the surface of the melts. The atoms clusters were generated by an ion beam bombarding on the Cu foil fixed above the alloy melts. The resultant microstructure reveals that the induced atom clusters exert great influence on the microstructural evolution of the highly undercooled eutectic and hypereutectic Ag-Ge alloys, but no obvious influence on the highly undercooled hypoeutectic alloy. The microstructural evolution and formation mechanism were analyzed and discussed.

Ductile Metallic Glasses in Supercooled Martensitic Alloys

We report ductile bulk metallic glasses based on martensitic alloys. The slowly cooled specimens contain a mixture of parent 'austenite' and martensite phase. The slightly faster cooled bulk metallic glasses with 2-5 nm sized 'austenite'-like crystalline cluster reveal high strength and large ductility (16%). Shear bands propagate in a slither mode in this spatially inhomogeneous glassy structure and undergo considerable 'thickening' from 5-25 nm. A 'stress induced displacive transformation' is proposed to be responsible for both plasticity and work-hardening-like behavior of these 'M-Glasses'.

Cu原子簇触发形核下的深过冷Ag-Ge合金组织演变研究

采用玻璃包覆的方法获得具有较大过冷度的亚共晶、共晶以及过共晶Ag-Ge合金熔体，并通过高能离子束轰击Cu箔产生Cu原子团簇溅射到过冷合金熔体中来触发非均质形核过程。凝固后合金显微组织的分析结果表明：在深过冷合金熔体中引入Cu原子团簇，它对亚共晶、共晶以及过共晶Ag-Ge合金的显微组织演变有着不同的影响效果，分析了显微组织的演变规律与形成机制。

A Thermodynamic Constitutive Model for Stress Induced Phase Transformation in Shape Memory Alloys

In this paper a thermodynamic constitutive model is developed for stress induced phase transformation in single crystalline and polycrystalline shape memory alloys (SMAs). Volume fractions of different martensite variants are chosen as internal variables to describe the evolution of microstructure state in the material. This model is then used in prediction the transformation behavior of a SMA (Cu-Al-Zn-Mn) under complex thermomechanical load (including complete and incomplete transformation in mechanical cycling, and proportional/non-proportional loading). (C) 2002 Elsevier Science Ltd. All rights reserved.

The mechanical properties of an aluminum alloy by plasma-based ion implantation and solution-aging treatment

The age-strengthening 2024 aluminum alloy was modified by a combination of plasma-based ion implantation (PBII) and solution-aging treatments. The depth profiles of the implanted layer were investigated by X-ray photoelectron spectroscopy (XPS). The structure was studied by glancing angle X-ray diffraction (GXRD). The variation of microhardness with the indenting depth was measured by a nanoindenter. The wear test was carried on with a pin-on-disk wear tester. The results revealed that when the aluminum alloys were implanted with nitrogen at the solution temperature, then quenched in the vacuum chamber followed by an artificial aging treatment for an appropriate time, the amount of AIN precipitates by the combined treatment were more than that of the specimen implanted at ambient temperature. Optimum surface mechanical properties were obtained. The surface hardness was increased and the weight loss in a wear test decreased too.

Transmission Electron Microscopy Characterization of Laser Welding Cast Ni-Based Superalloy K418 Turbo Disk And Alloy Steel 42Crmo Shaft

Microstructure characterization is important for controlling the quality of laser welding. In the present work, a detailed microstructure characterization by transmission electron microscopy was carried out on the laser welding cast Ni-based superalloy K418 turbo disk and alloy steel 42CrMo shaft and an unambiguous identification of phases in the weldment was accomplished. It was found that there are gamma-FeCrNiC austenite solid solution dendrites as the matrix, (Nb, Ti) C type MC carbides, fine and dispersed Ni-3 Al gamma' phase as well as Laves particles in the interdendritic region of the seam zone. A brief discussion was given for their existence based on both kinetic and thermodynamic principles. (c) 2007 Elsevier B.V. All rights reserved.

Deformation Behavior Of Fe-Based Bulk Metallic Glass During Nanoindentation

Fe-based bulk metallic glasses (BMGs) normally exhibit super high strength but significant brittleness at ambient temperature. Therefore, it is difficult to investigate the plastic deformation behavior and mechanism in these alloys through conventional tensile and compressive tests due to lack of distinct macroscopic plastic strain. In this work, the deformation behavior of Fe52Cr15Mo9Er3C15B6 BMG was investigated through instrumented nanoindentation and uniaxial compressive tests. The results show that serrated flow, the typical plastic deformation feature of BMGs, could not be found in as-cast and partially crystallized samples during nanoindentation. In addition, the deformation behavior and mechanical properties of the alloy are insensitive to the applied loading rate. The mechanism for the appearance of the peculiar deformation behavior in the Fe-based BMG is discussed in terms of the temporal and spatial characteristics of shear banding during nanoindentation.