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211.
《材料科学技术学报》2019,35(11):2600-2607
The MoNbTaTiV refractory high-entropy alloy(RHEA) with ultra-fine grains and homogeneous microstructure was successfully fabricated by mechanical alloying(MA) and spark plasma sintering(SPS).The microstructural evolutions,mechanical properties and strengthening mechanisms of the alloys were systematically investigated.The nanocrystalline mechanically alloyed powders with simple bodycentered cubic(BCC) phase were obtained after 40 h MA process.Afterward,the powders were sintered using SPS in the temperature range from 1500 ℃ to 1700 ℃.The bulk alloys were consisted of submicron scale BCC matrix and face-centered cubic(FCC) precipitation phases.The bulk alloy sintered at 1600℃ had an average grain size of 0.58 μm and an FCC precipitation phase of 0.18 μm,exhibiting outstanding micro-hardness of 542 HV,compressive yield strength of 2208 MPa,fracture strength of 3238 MPa and acceptable plastic strain of 24.9% at room temperature.The enhanced mechanical properties of the MoNbTaTiV RHEA fabricated by MA and SPS were mainly attributed to the grain boundary strengthening and the interstitial solid solution strengthening.It is expectable that the MA and SPS processes are the promising methods to synthesize ultra-fine grains and homogenous microstructural RHEA with excellent mechanical properties. 相似文献
212.
The thermodynamic assessment of the Al–Ir binary system was performed using the CALPHAD technique. The B2-AlIr phase was described, using the two sublattice model with the formula (Al,Ir,V a)1/2(Al,Ir,V a)1/2, while Al9Ir2, Al3Ir, Al13Ir4, Al45Ir13, Al28Ir9, and Al2.7Ir compounds were treated as stoichiometric compounds. The fcc-based phases (L10-AlIr, L12-Al3Ir, L12-AlIr3 and A1) were described using the four sublattice model with the formula, (Al,Ir)1/4(Al,Ir)1/4(Al,Ir)1/4(Al,Ir)1/4. From ab initio calculations (VASP) the formation enthalpies of the stable/metastable intermetallic phases involved in the Al–Ir system were estimated. The thermodynamic quantities, such as the phase equilibria, invariant reactions, and formation enthalpies of the intermetallic phases, were calculated using the obtained parameter set, and agree well with experimental data. 相似文献
213.
制壳耐火材料新秀--熔融石英--国外精铸技术进展述评(5) 总被引:3,自引:0,他引:3
陈冰 《特种铸造及有色合金》2005,25(5):294-297
介绍熔融石英作为制壳耐火材料在美国已大量采用,熔融石英具有密度小、热膨胀率低、透气性好、抗蠕变能力强、容易充型和脱壳等特点.对比了熔融石英和锆石的优缺点.由于熔融石英在价格和性能方面的优势,在我国精铸行业的推广应用具有迫切性和现实性. 相似文献
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215.
《Journal of the European Ceramic Society》2020,40(8):3314-3326
The feasibility to prepare alkali-activated materials starting from refractory wastes and their properties after exposure to high temperatures (800, 1000, 1200 and 1400 °C) were investigated. Two different aluminosilicate wastes were used: chamotte (CH, mainly composed of corundum, mullite and andalusite) and alumina-zirconia-silica (AZS, composed by baddeleyite, corundum and amorphous silica). Very high mechanical properties were achieved in both cases (28-days compressive strength of approx. 70 and 60 MPa for CH- and AZS-based pastes, respectively). Then, alkali-activated pastes were exposed to high temperatures. For both kinds of samples, a sharp increase of mechanical properties was obtained after exposure to 800 and 1000 °C thanks to the matrix densification. Above 1000 °C viscous sintering occurs leading to a further increase of mechanical properties. AZS-based materials were able to withstand high temperatures up to 1400 °C while CH-based pastes mechanical properties decrease at 1400 °C due to andalusite decomposition. 相似文献
216.
《Ceramics International》2020,46(9):13556-13568
This investigation deals with refractory monolithic materials that are broadly used in thermal treatment facilities as they are necessary e.g. for iron and steel, glass and cement production, thereby withstanding temperatures between 600 and 2000 °C. In the special case of hydraulic bond refractory castables, the components must be mixed with water for two reasons: firstly, to obtain a mouldable suspension; and secondly, to achieve a green strength via the hydraulic reaction of calcium aluminate cement that is high enough to enable a secure refractoriness of the concrete formwork. Prior to their first use in production, castables must have their pore water and hydraulic bond water carefully removed in order to avoid explosive spalling that can cause severe damages inside the furnaces.In this study, we investigate the one-dimensional drying behavior of two specific refractory castable compositions, a microsilica-containing low- and a no-cement castable (LCC/NCC) during first heat-up in the temperature regime between 20 and 300 °C. First results were already presented in a prior publication that demonstrate a specialized high-temperature Nuclear Magnetic Resonance (NMR) setup capable of continuously measuring moisture and temperature profiles on 74 mm-long cylindrical samples, without touching or moving the sample [1].In this paper we explore how the use of permeability-enhancing agents (fibers and MIPORE 20) beneficially affects the drying behavior and consequently allows higher heating rates. We also demonstrate that the NMR technique as applied here is sensitive enough to resolve differences in the dry-out behavior if said additives are used in the castable formulations.Our results demonstrate that incorporation of fiber and MIPORE 20 significantly alters the dry-out behavior. In particular, it can be resolved that as the fibers begin to melt, there is a noticeable increase in permeability that results in faster drying, as well as a decrease of the drying front temperature and therefore the generated maximum pressure. 相似文献
217.
《Journal of the European Ceramic Society》2023,43(6):2675-2689
The beneficial effects of adding nanostructured expandable graphite (EG) hybridized yttrium aluminium garnet (EG\YAG) powder as a composite reinforcement in improving the oxidation resistance, hot-strength, and microstructure development in Al2O3–MgO–C refractories were studied. The refractory components reinforced with EG\YAG exhibited more than 60% of oxidation resistance enhancement and as high as 200% increase in hot-strength performance over the standard refractories, formulated without EG\YAG. Correlating the damage parameter (DE) calculations based on ultrasonic measurements with residual strength data (Rc, Rb) showed that there was a progressive increase in Rc and Rb values with consistent reduction in the oxidative damage of EG\YAG reinforced refractories. Analysis indicated that these beneficial features were majorly ascribed to the in-situ development of bimodal microstructure with EG\YAG sintered framework throughout the refractory interior in these new class of reinforced systems. Additionally, the mechanism of toughening and implications of these results to materials design are discussed. 相似文献
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