共查询到20条相似文献,搜索用时 15 毫秒
1.
《Materials Science & Technology》2013,29(6):470-474
AbstractFour aluminium alloys of different zinc/magnesium ratio have been studied under various extrusion conditions. The alloys were cast in steel book moulds and subjected to initial thermomechanical treatments. Studies were made of hot extrusions and cold hydrostatic extrusions and in each case the changes in the extrusion parameters were analysed. An attempt has been made to explain some of the extrusion defects which appeared in various extruded sections. The extrusion speed was found to be crucial, since sections developed surface cracks at higher speeds. The extrusion speed was also found to vary inversely with the extrusion ratio, with higher speeds at low ratios. A well defined solute–depleted weld zone was observed on each of the four faces of a square tube extruded using a porthole die. Thermal treatment was not found to improve this weak weld zone. Tubes extruded using a floating-mandrel die withstood pressure testing up to 550 MPa.MST/43 相似文献
2.
The phase relations in the Bi–(Pb)–Sr–Ca–Cu–Sc–O system were studied near Bi2Sr2CaCu2O8 + (Bi-2212) and (Bi,Pb)2Sr2Ca2Cu3O10 + (Bi-2223) between 850 and 930°C. The introduction of Sc led to the formation of a new compound Sr2ScBiO6, which coexisted with Bi-2212 and Bi-2223. Using crystallization from a peritectic melt at different cooling rates, we obtained Bi-2212 matrix composites containing finely dispersed Sr1.9Ca0.1ScBiO6inclusions, with T
cattaining 89 K. The T
cof the Bi-2223–Sr1.9Ca0.1ScBiO6superconducting ceramic prepared by solid-state sintering of a Bi–(Pb)–Sr–Ca–Cu–Sc–O precursor was 108.5 K. 相似文献
3.
L. V. Makhnach S. P. Tolochko V. V. Vashuk O. V. Strukova O. P. Ol'shevskaya Yu. G. Zonov 《Inorganic Materials》2002,38(12):1258-1263
La2 – x
Ce
x
NiO
y
and Sr2 – x
Ce
x
NiO
y
materials were prepared, and their properties were studied. Nearly single-phase Sr2 – x
Ce
x
NiO
y
samples (tetragonal K2NiF4 structure) could be obtained at x= 0.25 and 0.3. The lattice parameters, weight change, relative length change, and electrical resistivity of Sr1.7Ce0.3NiO
y
were measured from 20 to 1000°C. The oxygen content of this material, determined by hydrogen reduction and iodometric titration, was found to vary widely, depending on heat-treatment conditions. The room-temperature resistivity of Sr1.7Ce0.3NiO
y
is (2–5) × 10–2 cm. In the range 20–450°C, this material exhibits n-type conductivity. Its thermoelectric power varies from –12 V/K at 20°C to –34 V/K at 450°C. The temperature variation of resistivity for Sr1.7Ce0.3NiO4 in the first heating–cooling cycle below 450°C is shown to depend on the thermal history of the sample. The resistivity reaches a maximum between 500 and 800°C. The structural and transport properties of the mixed oxide are shown to be correlated with its oxygen content. 相似文献
4.
《Materials Science & Technology》2013,29(12):1106-1114
AbstractThe short transverse fracture toughness of an Al–Li–Cu–Mg–Zr extrudate was determined as a function of aging condition and testing temperature. To elucidate the underlying micromechanisms, the short transverse fracture surfaces of the extrudate were characterised via scanning electron microscopy, grain boundary precipitates and precipitation free zones were identified via transmission electron microscopy, and segregation of elements to grain boundaries was analysed using secondary ion mass spectrometry. Three principal observations were made as follows. First, with increasing aging time, the short transverse toughness of the extrudate increased when tested at room temperature, but decreased at liquid N2 temperature, whereas with decreasing testing temperature, it remained essentially constant for the underaged condition, and decreased sharply for the peak aged and overaged tempers. Second, in addition to regions exhibiting shallow dimples, smooth ‘featureless’ zones were revealed on the short transverse fracture surfaces, which are intergranular in nature for all the specimens tested. The area fraction of the featureless regions decreased noticeably with increasing aging time when tested at room temperature, and increased markedly with decreasing testing temperature for the peak aged and overaged conditions. Third, segregation of Li, Si, Na, and H was detected for both the underaged and overaged specimens, and also of K for the underaged specimens only. In general, the enhancement of the room temperature short transverse toughness with aging and the negative effect of cryogenic temperature on fracture toughness are in obvious contrast to the in plane toughness behaviour reported in the literature, the featureless character of the short transverse fracture and its connection with poor toughness seldom having been emphasised. Based upon the present study, segregation induced brittleness is proposed as the critical micromechanism responsible for grain boundary weakness, and thus for the poor short transverse fracture toughness.MST/1829 相似文献
5.
Tobias Dubberstein Hans-Peter Heller Jens Klostermann Rüdiger Schwarze Jürgen Brillo 《Journal of Materials Science》2015,50(22):7227-7237
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 (dσ/dT) 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
6.
Roland E. Allen 《Journal of Modern Optics》2014,61(1):1-6
The particle recently discovered by the CMS and ATLAS collaborations at CERN is almost certainly a Higgs boson, fulfilling a quest that can be traced back to three seminal high-energy papers of 1964, but which is intimately connected to ideas in other areas of physics that go back much further. One might oversimplify the history of the features which (i) give mass to the W and Z particles that mediate the weak nuclear interaction, (ii) effectively break gauge invariance, (iii) eliminate physically unacceptable Nambu–Goldstone bosons, and (iv) give mass to fermions (like the electron) by collectively calling them the London–Anderson–Englert–Brout–Higgs–Guralnik–Hagen–Kibble–Weinberg mechanism. More important are the implications for the future: a Higgs boson appears to point toward supersymmetry, since new physics is required to protect its mass from enormous quantum corrections, while the discovery of neutrino masses seems to point toward grand unification of the non-gravitational forces. 相似文献
7.
《Composites Part B》2004,35(3):235-243
Magnetic investigations on a nanocomposite material obtained by spinning solutions of styrene–butadiene–styrene block copolymer containing barium ferrite nanoparticles onto Si wafers are reported. The effect of the spinning frequency on the magnetic features is discussed. It is observed that the magnetization at saturation is decreased as the spinning frequency is increased as the centrifuge force removes the magnetic nanoparticles from the solution. This is supported by the derivative of the hysteresis loops, which show two components, one with a high coercive field and another with a small coercive field. Increasing the spinning frequency increases the weight of the low coercive field component. The anisotropy in the distribution of magnetic nanoparticles, triggered eventually by the self-assembly capabilities of the matrix, is revealed by the difference between the coercive field in parallel and perpendicular configuration. It is noticed that increasing the spinning frequency enhances this difference. The effect of annealing the nanocomposite films is discussed. 相似文献
8.
《Materials Science & Technology》2013,29(6):757-761
AbstractThe casting properties of high strength Al-7Zn-7Mg-1Cu-3Ni-3Si(wt-%) alloy are described. Compared with common Al-Zn-Mg-Cu alloys, an improvement of casting properties has been achieved by adding elements (Ni, Mg, Si) that form eutectic phases, thus reducing the solidification interval of the alloy. A comparison of thermal cooling curves, castability and hot tearing tendency has been carried out for three alloys: Al-7Zn-2Mg-1Cu (structure consists mainly of solid solution), quasi-ternary eutectic alloy Al-7Zn-7Mg-1Cu-3Ni-3Si and the common casting alloy Al-10Si. In addition, the effect of melt protection against oxidation on castability has been evaluated. It is shown that the casting properties of the protected quasi-ternary eutectic alloy are significantly better than those of the common Al-7Zn-2Mg-1Cu alloy and that they achieve a level close to that of Al-10Si alloy. 相似文献
9.
《Materials Science & Technology》2013,29(7):587-591
AbstractResults are reported of an investigation of solid state transformations in a series of α2 based alloys having an aluminium content of 26 at.-% with carbon up to 3 at.-%; two α2 basedquaternary Ti–Al–Nb–C alloys with 5 and 12 at.-%Nb and 3 at.-%C were also studied. Ordering occurs in the ternary Ti–Al–C alloys and also in the 23Al–5Nb–3C alloy on quenchingfrom 1250°C. Additional carbide precipitation was not observed in the ternary Ti–Al–C alloys on reheating to 750°C. Additions of niobium resulted in the presence of the β phase at 1050°C in the 5%Nb alloy and at 1050 and 750°C in the 12%Nb alloy. In the quaternary Ti–Al–Nb–C alloys, (Ti, Nb)3AlC was found to be the primary phase and was present in the microstructure over the temperature range studied. In the 21Al–12Nb–3C alloy, the ordered β phase transformed to α″2 martensite on quenching from 1250;amp;#x00B0;C.MST/1306 相似文献
10.
Inorganic Materials - Isobaric–isothermal composition polyhedra of solid solutions existing in the Li–Ni–Mn–Co–O system at a temperature of 800°C and oxygen... 相似文献
11.
To further improve the wear resistance of Fe–Mn–Si–Cr–Ni based shape memory alloys, the effects of ageing at 1123 K with and without pre-deformation at room temperature on the precipitation of second-phase particles and their effects on wear resistance were investigated in an Fe–Mn–Si–Cr–Ni–Ti–C alloy. Results showed that the solution treated Fe–Mn–Si–Cr–Ni–Ti–C alloy exhibited much better wear resistance than the solution treated AISI 321 stainless steel; ageing with pre-deformation improved the wear resistance of Fe–Mn–Si–Cr–Ni–Ti–C alloy more effectively than ageing without pre-deformation, especially under the heavy load condition. 相似文献
12.
The p–T–x–y phase equilibria in the Cd–Zn–Te system are analyzed. The p–T and T–x–yprojections of the p–T–x–y phase diagram and a T–x–y isobar (for pressures at which Cd1–x
Zn
x
Te1 ± solid solutions sublime congruently in terms of Te) are mapped out. The key features of the sublimation behavior of the solid solution are examined. The p–T projection is studied by static vapor pressure measurements at temperatures from 700 to 1300 K and pressures of up to 101.3 kPa. The p–T sections of the phase diagram are constructed for x = 0.05, 0.10, 0.15, 0.25, 0.50, 0.75, 0.90, and 1. The solid solution containing 35 mol % ZnTe is found to phase-separate at 473 K. 相似文献
13.
Annealing Fe–P–Mn and Fe–P–Mn–V soft-magnetic amorphous alloys prepared from ferrophosphorus waste leads to the formation of fine-particle crystalline phases. The associated structural hardening is more pronounced in alloys with stronger interatomic interactions. The dissolution of Mn and V inhibits the growth of Fe3P particles, which become smaller than the -Fe particles. 相似文献
14.
The liquid–liquid interfacial tension in the ternary monotectic alloys Al34.5-x
Bi65.5Cu
x
and (Al0.345Bi0.655)100-x
Si
x
(mass%) has been determined as a function of its Cu (Si) content by a tensiometric technique. It is established that the
interfacial tension gradually increases when either Cu or Si is added to Al–Bi alloys. The increase of can be related to the increase of the miscibility gap (both width and height) when Cu (Si) is added to the Al–Bi binary.
The temperature dependences of the interfacial tension in binary Al34.5Bi65.5 and ternary Al23.25Bi65.5Cu11.25 and (Al0.345Bi0.655)95Si5 monotectic alloys are well described by the power function with the critical-point exponent . 相似文献
15.
目的 改善AZ91镁合金在温度超过120℃时的力学性能。方法 在AZ91合金中添加Ca、Si和La/Ce混合稀土元素。在360℃下等温挤压,平均挤压速度为1.2 mm/s,挤压比为30︰1,以探究Ca、Si和La/Ce混合稀土元素对AZ91合金力学性能、物相组成和显微组织等的影响。结果 在AZ91挤压态合金中,与添加Si元素相比,Ca元素对挤压态合金的力学性能影响更大。在室温时,Mg–9Al–Zn–0.5RE–Si挤压态合金的屈服强度、极限抗拉强度和伸长率分别是254 MPa、306MPa、7.0%,而Mg–9Al–Zn–0.5RE–0.5Ca挤压态合金的屈服强度、极限抗拉强度和伸长率分别是308 MPa、330 Ma、7.1%。Mg–9Al–Zn–0.5RE–0.5Ca–0.5Si挤压态合金室温力学性能最佳,其屈服强度、极限抗拉强度和伸长率分别是351 MPa、383 MPa、7.4%,说明Ca、Si这2种元素的协同作用可同时提高室温下AZ91合金的强度和塑性。在150℃和200℃下,Mg–9Al–Zn–0.5RE–0.5Ca–0.5Si合金仍然具有最佳的力学性能。在150℃下,其屈... 相似文献
16.
Gorshkov V. A. Kovalev D. Yu. Boyarchenko O. D. Sychev A. E. 《Inorganic Materials》2021,57(12):1300-1306
Inorganic Materials - We report high-temperature synthesis of cast composite materials in the Cr–Mo–Al–C system. (Cr1 – xMox)2AlC -based materials have been prepared for the... 相似文献
17.
We present experimental results on crosstalk of non-electrical origin between high frequency quartz tuning forks immersed in the same volume of helium gas, liquid or superfluid. We compare these results with various observations of other groups and propose an explanation of this puzzling phenomenon. To the best of our knowledge, notable crosstalk has only been observed in superfluid helium both in the two-fluid regime and at very low temperatures, but was rarely seen to behave in a systematic way. We demonstrate some of its most significant properties—amplitude dependence within a short time span, long-term temporal instability, effects of the geometry of the setup and of obstacles placed between the tuning forks. Although the results are not fully understood, as the most likely explanation, we ascribe the observations to the coupling of tuning forks to standing acoustic modes inside the experimental volume, emphasizing the importance of second sound for understanding the observations at temperatures within the two-fluid regime (1 K<T<2.17 K). Finally, we suggest simple precautions leading to suppression of excessive acoustic crosstalk between oscillating objects in He II. 相似文献
18.
《Materials Science & Technology》2013,29(9):816-823
AbstractThe hot deformation behaviour of an Al–Li–Mg–Zr alloy was characterised in hot torsion and extrusion. The alloy was found to have similar hot ductility to existing high strength aluminium alloys, but this could be maintained at higher temperatures. Billets were extruded over a range of process conditions and a limit diagram was constructed for surface cracking. All the extrusions were found to be partially recrystallised after deformation, but the volume fraction of recrystallisation was a strong function of billet temperature and extrusion ratio. In addition, the unrecrystallised areas contained a recovered substructure where the subgrain size was inversely proportional to the temperature compensated strain rate. The as extruded structure was retained during solution treatment and as a result final mechanical properties were strongly dependent on the extrusion conditions. The use of high billet temperatures and low extrusion ratios gave the best combination of strength and toughness.MST/839 相似文献
19.
20.
Dao-ming Lu 《Journal of Modern Optics》2019,66(4):424-429
In this paper, we consider the situation that three identical two-level atoms are separately trapped in the three single-mode cavities. Each atom resonantly interacts with cavity via a one-photon hopping. The dynamics of nonlocality in the system is investigated via Mermin–Ardehali–Belinksii–Klyshko inequality. The results show that when three atoms are initially in W state and three-cavity fields are in vacuum states both the quantum state of three atoms and that of three cavities all display nonlocality On the other hand, when three atoms are initially in Greenberger–Horne–Zeilinger state and three-cavity fields are in vacuum states, the quantum state of three atoms and that of three cavities all do not display nonlocality. 相似文献