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1.
Using an arc physical vapor deposition process, we have produced nanostructured Mo–Si–Al–Ti–Ni–N coatings with a multilayer architecture formed by Mo 2N, AlN–Si 3N 4, and TiN–Ni and a crystallite size on the order of 6–10 nm. We have studied the physicomechanical properties of the coatings and their functional characteristics: wear resistance, adhesion to their substrates, and heat resistance. According to high-temperature (550°C) wear testing and air oxidation (600°C) results, the coatings studied here are wearand heat-resistant under appropriate temperature conditions. Their properties are compared to those of Mo–Si–Al–N coatings. 相似文献
2.
The temperature dependence of surface tension and density for Fe–Cr–Mo (AISI 4142), Fe–Cr–Ni (AISI 304), and Fe–Cr–Mn–Ni TRIP/TWIP high-manganese (16 wt% Cr, 7 wt% Mn, and 3–9 wt% Ni) liquid alloys are investigated using the conventional maximum bubble pressure (MBP) and sessile drop (SD) methods. In addition, the surface tension of liquid steel is measured using the oscillating droplet method on electromagnetically levitated (EML) liquid droplets at the German Aerospace Centre (DLR, Cologne). The data of thermophysical properties for Fe–Cr–Mn–Ni is of major importance for modeling of infiltration and gas atomization processes in the prototyping of a “TRIP-Matrix-Composite.” The surface tension of TRIP/TWIP steel increased with an increase in temperature in MBP as well as in SD measurement. The manganese evaporation with the conventional measurement methods is not significantly high within the experiments (? Mn < 0.5 %). The temperature coefficient of surface tension (d σ/d T) is positive for liquid steel samples, which can be explained by the concentration of surface active elements. A slight influence of nickel on the surface tension of Fe–Cr–Mn–Ni steel was experimentally observed where σ is decreased with increasing nickel content. EML measurement of high-manganese steel, however, is limited to the undercooling state of the liquid steel. The manganese evaporation strongly increased in excess of the liquidus temperature in levitation measurements and a mass loss of droplet of 5 % was observed. 相似文献
3.
AbstractThe equilibrium phase diagrams of Al–Cr, Al–Zr, and Al–Cr-Zr, with particular reference to aluminium-rich alloys, have been critically reviewed. On the basis of these, and consistent with measured thermodynamic values, the binary systems have been thermodynamically characterized. Using these characterizations, phase equilibria have been extrapolated in the ternary, with the intention of augmenting the sparse experimental information concerning the equilibrium liquidus (0–10 at.%Cr, Zr) and solid solution range of aluminium in Al–Cr–Zr. Using the same parameters that define the equilibrium phase relationships, metastable phase relationships can also be extrapolated into the ternary.MST/418 相似文献
4.
Using an arc physical vapor deposition process, we have produced nanostructured Mo–Si–Al coatings with a uniform distribution of equiaxed grains 8–12 nm in size and Mo–Si–Al–N coatings with a multilayer structure and a modulation period from 22 to 25 nm. The former coatings consist of MoSi 2 and Mo and the latter consist of Mo2N and amorphous Si 3N 4 and AlN. The hardness of the Mo–Si–Al–N and Mo–Si–Al coatings is 41 and 18 GPa, respectively; they are similar in resistance to elastic deformation; and the Mo–Si–Al–N coating has a considerably higher resistance to plastic deformation. The coatings have roughly identical coefficients of friction (~0.67–0.69 at 20°C and ~0.52–0.56 at 550°C), but the wear resistance of the Mo–Si–Al–N coating is higher by three and two orders of magnitude at 20 and 550°C, respectively. The coatings of the two systems exhibit good adhesion to the substrate and cohesive fracture. Partial wear of the Mo–Si–Al and Mo–Si–Al–N coatings in the course of scratch testing occurs at indentation loads of 80 and 63 N, respectively. 相似文献
6.
Densities and their temperature coefficients of liquid Cr–Fe, Fe–Ni, and Cr–Ni binary alloys have been measured containerless using the technique of electromagnetic levitation. Data have been obtained in a wide temperature range including the supercooled region. The density measurements indicate that these binary systems have a small and positive excess volume, whereas the excess free energies are negative. The temperature coefficients of these alloys can be estimated from those of the pure components. Hence, possible contributions from the temperature dependence of the excess volume can be ignored to calculate the temperature coefficient of density. 相似文献
7.
AbstractHot rolled Al–6Li–1Cu–1Mg–0·2Mn (at.-%) (Al–1·6Li–2·2Cu–0·9Mg–0·4Mn, wt-%) and Al–6Li–1Cu–1Mg–0·03Zr (at.-%) (Al–1·6Li–2·3Cu–1Mg–0·1Zr, wt-%) alloys developed for age forming were studied by tensile testing, electron backscatter diffraction (EBSD), three-dimensional atom probe (3DAP), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). For both alloys, DSC analysis shows that ageing at 150°C leads initially to formation of zones/clusters, which are later gradually replaced by S phase. On ageing at 190°C, S phase formation is completed within 12 h. The precipitates identified by 3DAP and TEM can be classified into (a) Li rich clusters containing Cu and Mg, (b) a plate shaped metastable precipitate (similar to GPB2 zones/S″), (c) S phase and (d) δ′ spherical particles rich in Li. The Zr containing alloy also contains β′ (Al 3Zr) precipitates and composite β′/ δ′ particles. The β′ precipitates reduce recrystallisation and grain growth leading to fine grains and subgrains. 相似文献
8.
Titanium is used due its excellent properties in medical and dentistry areas. With the objective of exploiting better mechanical
properties, not altering its biocompatibility, it was intended to add niobium and zirconium to the titanium, being formulated
two alloys Ti–35%Nb–5%Zr (alloy 1) and Ti–35%Nb–10%Zr (alloy 2) wt% produced by an arc melting method. The chemical analysis
of the samples was accomplished by X-ray fluorescence, and the microstrutural evaluation by scanning electron microscopy and
X-ray diffraction. The mechanical tests were: Vickers hardness, tensile strength, mechanical cycling, and fracture analysis.
The results allowed characterizing the alloy 1 as α + β type and the alloy 2 as β type. It is found that the alloy 1 presented
larger hardness and smaller tensile strength than the alloy 2. The fractures, after the tensile test, were of the ductile
type and, after the mechanical cycling, they were of the mixed type for both alloys. 相似文献
9.
Metal–semiconductor Zn–ZnO core–shell microcactuses have been synthesized on Si substrate by simple thermal evaporation and condensation route using NH 3 as carrier gas at 600 °C under ambient pressure. Microcactuses with average size of 65–75 μm are composed of hollow microspheres with high density single crystalline ZnO rods. The structure, composition and morphology of the product were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapor–liquid–solid (VLS) based growth mechanism was proposed for the formation of Zn–ZnO core–shell microcactuses. Room temperature photoluminescence (PL) investigations revealed a strong and broad blue emission band at 441 nm associated with a weak ultraviolet (UV) peak at 374 nm. This blue emission (BE) is different from usually reported green/yellow-green emission from Zn–ZnO or ZnO structures. The field emission (FE) measurements exhibited moderate values of turn-on and threshold fields compared with reported large field emissions for other materials. These studies indicate the promise of Zn–ZnO core–shell microcactuses for the applications in UV-blue light display and field emission microelectronic devices. 相似文献
10.
Journal of Materials Science - Ti–26Nb–2Fe–(0, 2, 4, 6, 8)Sn alloys were prepared by arc melting and subjected to homogenization, cold rolling, and solution treatment. The β... 相似文献
11.
Three types of composite nanotube heterostructures (two double-layered and one triple-layered structure) are synthesized by
simple heat treatment, forming SiC–SiO 2, C–SiO 2, and C–SiC–SiO 2 composite coaxial nanotubes. These multilayered composite nanotubes consist of several components with different electrical
properties, for example, metal, semiconductor, and insulator components. In particular, C–SiC–SiO 2 triple-layered nanotubes with metallic, semiconducting, and insulating layers are synthesized for the first time. These multilayered
nanotubes can be expected to find applications in nanoscale heterostructure electronic and optical devices. 相似文献
12.
We have performed thermodynamic calculation of the phase equilibria in the ternary monotectic system Al–Bi–Si. The liquid–liquid
miscibility gap in the Al–Bi–Si system extends over almost the entire concentration triangle. The thermal analysis data for
(Al 0.345Bi 0.655) 100−x
Si
x
alloys ( x = 2.5, 5, 7.5, and 10 wt%) excellently agree with the calculated phase diagram. The experimental density difference of the
coexisting liquid phases shows a good agreement with the density difference calculated in the approximation of ideal solution
using the densities of pure elements and the compositions of L ′ and L ′′ from the thermodynamic calculation. The liquid–liquid interfacial tension in the (Al 0.345Bi 0.655) 100−x
Si
x
liquid alloys increases with Si content. The experimental temperature dependence of the interfacial tension is well described
by the power low in reduced temperature ( T
C– T) at approach of the critical temperature with the exponent μ = 1.3, which is close to the value predicted by the renormalization
group theory of critical behavior. 相似文献
14.
The first results of manufacturing and investigations of a new type of nanocomposite protective coatings are presented. They were manufactured using a combination of two technologies: plasma-detonation coating deposition with the help of plasma jets and thin coating vacuum-arc deposition. We investigated structure, morphology, physical and mechanical properties of the coatings of 80–90 μm thickness, as well as defined the hardness, elastic Young modulus and their corrosion resistance in different media. Grain dimensions of the nanocomposite coatings on Ti–N–Cr base varied from 2.8 to 4 nm. The following phases and compounds formed as a result of plasma interaction with the thick coating surface were found in the coatings: Ti–N–Cr (200), (220), γ-Ni 3–Fe, a hexagonal Cr 2–Ti, Fe 3–Ni, (Fe, Ni)N and the following Ti–Ni compounds: Ti 2Ni, Ni 3Ti, Ni 4Ti, etc. We also found that the nanocomposite coating microhardness increased to H = 31.6 ± 1.1 GPa. The Young elastic modulus was determined to be E = 319 ± 27 GPa – it was derived from the loading–unloading curves. The protective coating demonstrated the increased corrosion resistance in acidic and alkaline media in comparison with that of the stainless steel substrate. 相似文献
15.
Lead-free alloys have attracted great attentions recently due to the toxic nature of lead for the human body. In this study, low amounts of Mg and Sb were added to the Cu65–Zn35 brass and microstructure, mechanical properties and machinability of samples were compared to Cu65–Zn35 brass. Both Mg and Sb led to the promotion of β′ phase as well as the formation of new ternary copper rich intermetallic particles. It was found that these particles had a significant role in the reduction of the ultimate tensile strength, toughness, work hardening and elongation while increasing the hardness of samples. Results of machinability evaluation of samples showed that the cutting forces were decreased significantly and morphology of chips were improved compared to Cu65–Zn35 brass sample. 相似文献
16.
A study of the synthesized Ge22.5Bi7S70.5 glassy system has been carried out. Differential thermal analysis data indicate the retention in the as-quenched sample of two amorphous phases. Thermal conductivity, , measurements on bulk sample reveal that the main contribution to is due to phonon thermal conductivity. Thermal evaporation of the synthesized ingot gives films with Ge20.7Bi6.8S72.5 as composition. The values of the activation energy and the pre-exponential factor calculated from the direct current electrical conductivity above 53 °C suggest that carrier conduction occurred between extended states in these films. The I–V characteristics in the off-state and the switching phenomenon are investigated. A memory switch with a threshold voltage decreasing with temperature is detected for the studied films. Optical parameters such as absorption coefficient, optical gap and refractive index are also determined. Comparison with binary Ge–S glass reveals that the addition of Bi introduces additional absorbing states at band edges. © 1998 Kluwer Academic Publishers 相似文献
17.
The 1070-K phase relations in the M–Mn–P (M = Cr, Mo, W; 67 at. % P) and Re–Mn–P (50 at. % P) systems were studied by x-ray diffraction. The existence of the known phosphides Mo 4Mn 6P 5 and (Mn,W) 12P 7 was confirmed, and a new phase with the general formula (Mn,Mo) 12P 7 and stoichiometry range Mo 4.6–1.8Mn 7.4–10.2P 7 was identified. Its structure was determined by powder diffraction profile analysis ( R = 0.074): Cr 12P 7 structure type, sp. gr. P6, a = 0.94929(8) nm and c = 0.33565(3) nm for Mn 7.4Mo 4.6P 7. The Mo and Mn atoms in the structure of this phase were shown to occupy all positions at random. In addition to the known solid solutions (Cr,Mn) 3P (Ni 3P structure type), (Cr,Mn) 12P 7 (Cr 12P 7), (Cr,Mn)P, and (Mn,Mo)P (MnP), we revealed new solid-solution series: (Cr,Mn) 2P (Cr 2P), (Mn,Cr) 2P (Fe 2P), (Mn,Mo) 3P (Ti 3P), (Mo,Mn) 3P (-V 3S), (Mo,Mn)P (WC), (W,Mn)P (MnP), (Mo,Mn)P 2, and (W,Mn)P 2 (MoP 2). The Re–Mn–P system was found to contain neither ternary phosphides nor solid solutions. 相似文献
18.
Intermetallic Ti–45Al–8Nb–(W, B, Y) (at.%) alloys were directionally solidified at growth rates of 10–400 μm/s with a Bridgeman type apparatus. Microstructures and room temperature (RT) mechanical properties of the directionally solidified (DS) alloys were investigated. The microstructures with different segregation morphologies were observed at different growth rates. Fully lamellar (FL) microstructure evolves into a massive microstructure when the growth rate is up to 100 μm/s. Both the width of columnar grain and the interlamellar spacing decrease with increasing growth rate. Compressive properties were not proportional to the growth rates but closely related to the segregation morphologies. Only the DS alloy with columnar pattern of Al-segregation had tensile ductility. A better RT tensile plastic elongation level of 2% and yield strength 475 MPa were obtained at growth rate of 10 μm/s. Cracks propagated in transgranular mode predominantly. Larger elongated B2 particles produced in the interdendritic regions were detrimental to the tensile ductility of the DS alloy. 相似文献
19.
The microstructure evolution and mechanical properties of biodegradable Mg–3Sn–1Zn–0.5Mn alloys were investigated by the optical microscopy, X-ray diffractometer and a universal material testing machine.The corrosion and degradation behaviors were studied by potentiodynamic polarization method and immersion test in a simulated body fluid(SBF). It was found that the as-extruded Mg–3Sn–1Zn–0.5Mn alloy has the fine equiaxed grains which underwent complete dynamic recrystallization during the hot extrusion process, with the second phase particles of Mg_2Sn precipitated on the grain boundaries and inside the grains. The tensile strength and elongation of as-extruded Mg–3Sn–1Zn–0.5Mn alloys were 244 ± 3.7 MPa and 19.3% ± 1.7%, respectively. The potentiodynamic polarization curves in SBF solution indicated the better corrosion resistance of the as-extruded Mg–3Sn–1Zn–0.5Mn alloy in the SBF solution. Immersion test in the SBF solution for 720 h revealed that the corrosion rate of as-extruded Mg–3Sn–1Zn–0.5Mn alloy was nearly 4 ± 0.33 mm/year. The hemolysis rate of as-extruded Mg–3Sn–1Zn–0.5Mn alloy was lower than the safe value of 5% according to ISO 10993-4. As-extruded Mg–3Sn–1Zn–0.5Mn alloy showed good biocompatibility after being implanted into the dorsal muscle and the femoral shaft of the rabbit, and no abnormalities were found after short-term implantation. It was revealed that the as-extruded Mg–3Sn–1Zn–0.5Mn alloy is a promising material for biodegradable implants,which possesses an interesting combination of preferred mechanical properties, better corrosion resistance and biocompatibility. 相似文献
20.
It is established that the energy of deposited particles influences the structure, composition, and properties of multilayer nitride coatings consisting of alternating layers of nanocrystalline TiN and amorphous Si3N4 phases with inclusions of nanocrystalline hexagonal AlN formed at energies of titanium, aluminum, and silicon ions exceeding ~317 × 10–19, 267 × 10–19, and 230 × 10–19 J, respectively. As the energy of titanium ions bombarding the substrate increases above ~512 × 10–19 J, the phase transition from disordered TiN
x
to Ti3N2 and the appearance of 2- to 3-nm-thick sublayers in 15-nm-thick nanocrystalline TiN
x
layers take place in the coating. The maximum hardness of such coatings reaches a level of ~54 GPa. 相似文献
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