Microstructure and properties of TiB2–TiB reinforced titanium matrix composite coating by laser cladding

TiB₂ particle and TiB short fiber reinforced titanium matrix composite coatings were prepared utilizing in situ synthesized technique by laser cladding on the surface of Ti6Al4V alloy. Through the experiment, it was found that the surface of the single-track coatings appeared in the depression, but it can be improved by laser track overlapping. With the increase of laser power density, the amount of TiB short fiber was increased, and the distribution of TiB₂ and TiB became more uniform from the top to bottom. The micro-hardness of TiB₂/TiB coating showed a gradient decreasing trend, and the average micro-hardness of the coatings was two-fold higher than that of the substrate. Due to the strengthening effect of TiB₂ particle and TiB short fiber, the wear volume loss of the center of the coating was approximately 30% less than that of the Ti–6Al–4V substrate, and the wear mechanism of the coating was mild fatigue particle detachment.     

Formation of the structure and physicomechanical properties of a quasicrystalline Al–Cu–Fe alloy upon plasma spraying

Quasicrystalline coatings prepared under various thermal conditions of spraying have been studied. Initial quasicrystalline powders with dispersion of 10–50 μm were prepared in a low-pressure arc discharge plasma. The coatings have been sprayed on copper rings using a swinging plasmatron. It is found that the increase in the quenching rate of melt droplets increases the chemical homogeneity and leads to formation of nanostructured formations. The precipitation of nanostructured grains (d < 100 nm) in the sprayed alloy leads to an increase in the mechanical characteristics (hardness, deformation, and ductility) and can be considered as an additional factor of hardening of the material.     

Investigation on the undercooling and crystallization of Ni–Fe alloy coating melt by DSC

The undercooling of Ni–Fe alloy coating melt was in situ investigated by differential scanning calorimeter with flux processing technique. The highest undercooling of Ni–Fe alloy with 426 K was obtained as the thermal treatment temperature of the melt being 1904 K and the cooling rate being 50 K min^?1. When cooling rate is fixed, the undercooling depends on the melt processing temperature, and increases rapidly at the first stage. The effects of thermal treatment temperature and cooling rates on the undercooling were discussed.     

Laser glazing study of Co-based alloy and Ni-Nb-Cr alloy coating

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Microstructure and physical properties of bismuth–lead–tin ternary eutectic alloy

Using different experimental techniques, microstructure, electrical resistivity, attenuation coefficient, and mechanical and thermal properties of the quenched Bi–Pb–Sn ternary eutectic alloy have been investigated. From the X-ray analysis, Bi₃Pb₇ and Bi–Sn meta-stable phases are detected, in addition to rhombohedral bismuth and Sn body-centered tetragonal phases. This study also compared the physical properties of the Bi–Sn–Pb ternary eutectic alloys with the base binary Bi–Sn and Bi–Pb eutectic alloys.     

Effect of irradiation and pre-ageing temperature on the mechanical properties of Al–Si alloy

Al–1wt.%Si alloy samples in the solid solution state were irradiated with doses of gamma rays up to 1.75 MGy for 2 h in the temperature range from 423 to 553 K. Induced variations in structure, mechanical and electrical properties were traced by suitable techniques. Observed changes in the measured parameters, internal friction Q ^?1, thermal diffusivity D _th, dynamic elastic modulus Y and resistivity, ρ, were explained in terms of the role and mode of interaction of lattice defects in irradiated and thermally treated samples. Composition inhomogeneity and variations in mass distribution in the matrix were also considered. The structure identification of the samples was carried out by using conventional X-ray diffraction techniques and transmission electron microscopy micrographs.     

Influence of annealing on the structure of nanoporous oxide films on the surface of titanium‒aluminum powder alloy

Oxide films obtained during anodization of Ti?40% Al sintered powder samples in fluorine-containing electrolytes are investigated. With scanning electron microscopy and X-ray phase analysis, it is demonstrated that an X-ray amorphous nanoporous anodic oxide film is formed on the surface of the powder microparticles under optimal anodization conditions. After annealing at T = 1093 K in air and vacuum (10^?2 Pa), the oxide films are revealed to crystallize with its regular porous structure retained. The composition of the polycrystalline anodic-oxide films annealed in air is a mixture involving TiO₂ (anatase and rutile) and α- and γ-Al₂O₃ phases and Ti₂O₃ and Al₂TiO₅ traces. The vacuum annealing process makes it possible to identify TiO₂, in which anatase is the main phase, α- and γ-Al₂O₃, and Ti₂O₃ and TiO traces. However, rutile is not revealed. The presented results indicate that the application of the anodic nanostructuring of Ti?40% Al powders is promising for the obtainment of new photocatalytic active nanomaterials.     

Influence of γ radiation on the structure-sensitive properties of CuTi amorphous alloy

The influence of small doses of radiation on the structure-sensitive properties of CuTi amorphous metallic alloy (AMA) is investigated. The AMA exhibit brittle behavior. It is found that, in samples exposed to radiation, the nonlinear behavior of the load-elongation curve is more pronounced and begins sooner. A small change in the fracture morphology in these samples is observed by raster electron microscopy. The additional broadening of the first amorphous maximum and its shift on the x-ray diffraction patterns correlates with increase in the dose. The modification of the structural-relaxation processes on heating the initial and irradiated samples is traced by the acoustic-emission method. The activation energy of these processes is determined.Tomsk State Architectural and Building Academy. Translated from Izestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 55–59, August, 1994.     

Tribological and mechanical properties of composites based on ethylene-tetrafluoroethylene and quasicrystalline Al−Cu−Fe filler

Samples of composites, in which ethylene-tetrafluoroethylene copolymer is used as a matrix and quasicrystalline Al?Cu?Fe powder as a filler with 0, 1, 2, 4 and 8 vol % concentrations, are prepared. Electron microscopy studies of the sample structure are carried out. The influence of the filler on the crystallinity and temperatures of sample melting and destruction is investigated. The mechanical and tribological properties of the samples are tested. It is found that an increase in the filler content changes neither the mechanical nor thermodynamic characteristics of the material but significantly improves the tribological characteristics. The friction coefficient decreases twice at 1 vol % of the filler and the wear resistance increases by 40 times at 8 vol %. Experimental data indicate the probability of good adhesion of the filler particles to the fluoropolymer matrix. The composites under investigation may be of interest as promising materials for polymer friction bearings.     

Dependence of the specific energy of the β/α interface in the VT6 titanium alloy on the heating temperature in the interval 600–975°C

The specific energy of interphase boundaries is an important characteristic of multiphase alloys, because it determines in many respects their microstructural stability and properties during processing and exploitation. We analyze variation of the specific energy of the β/α interface in the VT6 titanium alloy at temperatures from 600 to 975°C. Analysis is based on the model of a ledge interphase boundary and the method for computation of its energy developed by van der Merwe and Shiflet [33, 34]. Calculations use the available results of measurements of the lattice parameters of phases in the indicated temperature interval and their chemical composition. In addition, we take into account the experimental data and the results of simulation of the effect of temperature and phase composition on the elastic moduli of the α and β phases in titanium alloys. It is shown that when the temperature decreases from 975 to 600°C, the specific energy of the β/α interface increases from 0.15 to 0.24 J/m². The main contribution to the interfacial energy (about 85%) comes from edge dislocations accommodating the misfit in direction [0001]_α || [110]_β. The energy associated with the accommodation of the misfit in directions \({\left[ {\bar 2110} \right]_\alpha }\left\| {{{\left[ {1\bar 11} \right]}_\beta }} \right.\) and \({\left[ {0\bar 110} \right]_\alpha }\left\| {{{\left[ {\bar 112} \right]}_\beta }} \right.\) due to the formation of “ledges” and tilt misfit dislocations is low and increases slightly upon cooling.     

Microstructure and magnetic properties of atmospheric plasma sprayed Fe–40Al coating obtained from nanostructured powders

Amorphous and nanocrystalline materials have attracted much interest in the field of new materials design because of their excellent mechanical and physical properties as well as their magnetic properties. In this work, Fe–40Al coatings were prepared from nanostructured feedstock with a very low degree of order using atmospheric plasma spraying. Scanning electron microscopy, X-ray diffraction, and magnetic measurements were used to investigate microstructure, phase structure, and magnetic properties of the coatings. The results showed that Fe–40Al coating presented a ferromagnetic character due to partial structure with a low degree of order and unmelted nanostructured particles retained from the feedstock. Moreover, the heterogeneous magnetic properties were found in the parallel and vertical direction of the coating.     

Microstructure and mechanical properties of V–4Ti–4Cr alloy as a function of the chemical heat treatment regimes

The regularities of the formation of a heterophase structure and mechanical properties of V–4Ti–4Cr alloy as a function of thermomechanical and chemical heat treatments are studied. The regimes of thermomechanical treatment which provide the formation of a heterophase structure with a homogeneous volume distribution of oxycarbonitride nanoparticles with a size of about 10 nm and an increase in the volume content and thermal stability of this phase and which provide an increase in the temperature of alloy recrystallization are developed. The formation of the heterophase structure results in a substantial (up to 70%) increase in the short-term high-temperature strength of the alloy at T = 800°C. The increase in the strength is achieved while keeping a rather high level of plasticity.     

Sonocatalytic injury of cancer cells attached on the surface of a nickel–titanium dioxide alloy plate

The present study demonstrates ultrasound-induced cell injury using a nickel–titanium dioxide (Ni–TiO₂) alloy plate as a sonocatalyst and a cell culture surface. Ultrasound irradiation of cell-free Ni–TiO₂ alloy plates with 1 MHz ultrasound at 0.5 W/cm² for 30 s led to an increased generation of hydroxyl (OH) radicals compared to nickel–titanium (Ni–Ti) control alloy plates with and without ultrasound irradiation. When human breast cancer cells (MCF-7 cells) cultured on the Ni–TiO₂ alloy plates were irradiated with 1 MHz ultrasound at 0.5 W/cm² for 30 s and then incubated for 48 h, cell density on the alloy plate was reduced to approximately 50% of the controls on the Ni–Ti alloy plates with and without ultrasound irradiation. These results indicate the injury of MCF-7 cells following sonocatalytic OH radical generation by Ni–TiO₂. Further experiments demonstrated cell shrinkage and chromatin condensation after ultrasound irradiation of MCF-7 cells attached on the Ni–TiO₂ alloy plates, indicating induction of apoptosis.     

Laser irradiation effects on the surface,structural and mechanical properties of Al–Cu alloy 2024

Laser irradiation effects on surface, structural and mechanical properties of Al–Cu–Mg alloy (Al–Cu alloy 2024) have been investigated. The specimens were irradiated for various fluences ranging from 3.8 to 5.5 J/cm² using an Excimer (KrF) laser (248 nm, 18 ns, 30 Hz) under vacuum environment. The surface and structural modifications of the irradiated targets have been investigated by scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. SEM analysis reveals the formation of micro-sized craters along the growth of periodic surface structures (ripples) at their peripheries. The size of the craters initially increases and then decreases by increasing the laser fluence. XRD analysis shows an anomalous trend in the peak intensity and crystallite size of the specimen irradiated for various fluences. A universal tensile testing machine and Vickers microhardness tester were employed in order to investigate the mechanical properties of the irradiated targets. The changes in yield strength, ultimate tensile strength and microhardness were found to be anomalous with increasing laser fluences. The changes in the surface and structural properties of Al–Cu alloy 2024 after laser irradiation have been associated with the changes in mechanical properties.     

Microstructure and magnetic properties of a two-phase alloy of α-Fe and metastable Fe3B

Applying the hypercooling technique, the metastable-phase Fe₃B, instead of the stable-phase Fe₂B, is formed directly in the bulk Fe-B eutectic alloy melt and can be further preserved at room temperature. Measurement of magnetic properties shows that, for the bulk Fe-B eutectic alloy with Fe₃B phase, the intrinsic coercivity and retentivity become smaller, and the saturation magnetization is larger, than the stable eutectic alloy (α-Fe/Fe₂B) and some Fe-B amorphous alloys.     

Antireflection properties of germanium–carbon coating on zinc supplied substrate

In this research, germanium–carbon coatings were deposited on ZnS and glass substrates by a RF plasma enhanced chemical vapor deposition method using GeH₄ and CH₄ as precursors. ZnS/Ge_1?xC_x double-layer antireflection coating with optical thickness of one quarter wavelength was designed. The samples were characterized by fourier transform infrared spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy and nanoindentation. The coatings exhibited a structure free of pores with a very good adhesion to substrate. Based on the XRD patterns, no diffraction peak was found, so all the coatings mainly had an amorphous structure. The infrared (IR) transmittance spectrum show that the maximum IR transmittance in the band of 1030–1330 cm^?1 was about 84.6%, which is higher than ZnS substrate by 10%. In addition, the reflection of ZnS substrate is about 25%. This system has reduced the reflection from the substrate by 15%.     

PVdF-HFP membranes for fuel cell applications: effects of doping agents and coating on the membrane’s properties

Poly(vinylidene fluoride-co-hexafluoropropene)–hexafluoropropylene (PVdF-HFP; M _n, 130,000)-based membranes were prepared by means of phase inversion technique by coagulating with water and MeOH and then doping with H₃PO₄ and H₂SO₄. In order to improve the electrochemical properties of the PVdF-HFP membranes, coagulated membranes were also coated with polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PSEBS) and sulfonated with chlorosulfonic acid in the second stage. The effects of the type of coagulant, coagulation time, doping agents, coating, and sulfonation on the membrane properties were investigated. Membranes were thermally stable up to 400 °C. The conductivity values were measured to be between 1.10E???01 and 6.00E???03 mS/cm for uncoated samples. The proton conductivity value of the PSEBS-coated and sulfonated membrane was increased from 6.00E???03 to 92.1 mS/cm. Water uptake values varied from 0 to 38 % for uncoated samples and from 11.5 to 65.2 % for coated samples. Chemical degradation of PVdF-HFP membranes was investigated via Fenton test. All membranes were found to be chemically stable. Morphology of the membranes was examined by scanning electron microscopy. Different membrane morphologies were observed, depending on different membrane preparation procedures.     

Preparation and high-temperature properties of Au nano-particles doped α-Al2O3 composite coating on TiAl-based alloy

Au nano-particles doped α-Al₂O₃ composite coatings were successfully prepared on TiAl-based alloy by electrodeposition, using the Al₂O₃ sols with minor addition of HAuCl₄ solution. The even distribution of Au nano-particles (<2.0 wt.%) in the α-Al₂O₃ matrix has been observed. Isothermal oxidation tests of the samples coated with the as-prepared novel coatings at 900 °C in static air for 200 h shown that the oxygen inward diffusion can be effectively suppressed to a low level. The results of high-temperature cyclic oxidation test at 900 °C in air revealed that the oxidation and spallation resistance of TiAl-based alloy were improved significantly under thermal cycling. In the as-prepared coatings, cracks were shielded by means of crack bridging and the fracture resistance of the formed scales can be improved by toughening effects of the composite structure. Surface scratching tests after the cyclic oxidation exhibited that the adhesion of the formed composite scale on TiAl-based alloy was remarkably improved by the Au nano-particles doped α-Al₂O₃ composite coating.     

Influence of alloying elements on structure and some physical properties of quenched Sn–Sb alloy

We study the influence of ternary and quaternary alloying elements (Pb, Cd, Cu or Cu–Pb and Cu–Cd) on structural, electrical, hardness and other mechanical properties of Sn–Sb alloys (using an X-ray diffractometer and optical microscope, the double bridge method, Vickers hardness tester and the dynamic resonance method) to produce the best alloy for bearing applications. Adding Cu or Pb to Sn–Sb alloys improves their bearing properties, such as the mechanical properties (elastic modulus, internal friction, hardness and fracture strain) and thermal conductivity. Also, adding Cu, Pb or Cu–Pb to Sn–Sb alloys makes them excellent in their bearing applications and environmental hazards when compared with the Pb ₈₈Sn ₁₀Cu ₂ alloy for automotive applications (FIAT Normalizzazione) and the lead-based Babbitt bearing alloy.