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| 1 | Effects of Alumina on Cristobalite Crystallization and Properties of Silica-Based Ceramic Cores显示文摘In this work, the influences of alumina addition on cristobalite crystallization and properties of injection molded silica-based ceramic cores were investigated. X-ray diffraction(XRD) was used to characterize phase transformations in the samples, and the XRD result indicated that the addition of alumina promoted crystallization of fused silica during sintering at 1180–1220 °C and thus increases the amount of cristobalite. The increased amount of cristobalite as well as alumina addition led to much more thermal dilation due to their higher coefficients of thermal expansion than that of fused silica. The flexural strengths at room temperature and 1500 °C were tested, and it was shown that alumina addition could not affect room temperature strength, but decreased the flexural strength at 1500 °C. In addition, deflection resistance during heating to high temperatures was investigated, and the result indicated that alumina addition speeded up high temperature softening of the samples. XRD and scanning electron microscopy equipped with energy dispersive spectrometry(SEM/EDS) analysis suggested that this softening behavior was related with viscous flow sintering which could be accelerated by the reaction of alumina and silica with a product of mullite. | J.J.Liang Q.H.Lin X.Zhang T.Jin Y.Z.Zhou X.F.Sun B.G.Choi I.S.Kim J.H.Do C.Y.Jo | 2017 | Journal of Materials Science & Technology2017，33，2： | 14 |
| 2 | Effects of rejuvenation heat treatment on microstructure and creep property of a Ni-based single crystal superalloy显示文摘Both surface and internal microstructures of a second-generation Ni-based single crystal(SX) superalloy were studied after creep and rejuvenation heat treatment(RHT).It is indicated that the microstructures,such as the dislocation network,the γ phase and the γ' phase,can be recovered to those after the standard heat treatment(SHT).It is found that RHT affected zone(RAZ) formed at the surface is composed of theγ'-free layer,the transition layer and the recrystallization(RX),which are less than 20 μm in depth totally.Such depth of the RAZ doesn't affect the properties of the superalloy.The morphology of γ' phase at the RAZ is related to the composition of the elements.The average creep life after RHT is close to the average life after SHT.It is concluded that RHT could effectively repair SX parts and increase the total life of the sample after a damage by creep. | K.J.Tan X.G.Wang J.J.Liang J.Meng Y.Z.Zhou X.F.Sun | 2021 | Journal of Materials Science & Technology2021，，1： | 0 |
| 3 | Stress-rupture behavior of a Re-containing Ni-base single crystal superalloy at high temperatures显示文摘A Re-containing Ni-base single crystal superalloy was used to investigate the elementary processes associated with stress-rupture behavior at different temperatures where theγʹrafting occurs.At 900°C,the rupture behavior is mainly determined by the multiplication of dislocations within the wideningγchannels,which is closely linked with the propagation of microcracks along the inherentγ/γʹinterfaces.The rapid formation of lamellaγ/γʹraft structure,along with the developed-well interfacial dislocation networks,and its elastic instability are primarily responsible for the rupture behavior at 1100°C.There is a clear curvature tendency in the Larson-Miller plot of stress-rupture lifetime in relation to stress at high temperatures.It indicates that the influence extent ofγʹrafting on stress-rupture behavior is sensitive to the acting conditions of temperature and stress. | G.L.Wang D.Q.Qi J.L.Liu J.D.Liu J.G.Li Y.Z.Zhou X.F.Sun | 2023 | Journal of Materials Science & Technology2023，，32： | 0 |
| 4 | Sample selection for models to represent ceramic cores fabricated by stereolithography three-dimensional printing显示文摘Ceramic cores with good chemical stability and moderate mechanical properties near casting temperatures of 1550℃ for example are used for the manufacturing of internal structures of hollow blades,requiring complex structures and high precision[1–3].However,traditional preparation method based on investment casting is tedious,requiring not only long production cycles but also high cost[4]. | X.L.An J.J.Liang J.G.Li J.W.Chen Y.Z.Zhou X.F.Sun | 2022 | Journal of Materials Science & Technology2022，，26： | 0 |
| 5 | High-temperature fatigue strength of grain boundaries with different misorientations in nickel-based superalloy bicrystals显示文摘Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys. | D.F.Shi Z.J.Zhang Y.H.Yang Y.Z.Zhou R.Liu P.Zhang Z.F.Zhang | 2023 | Journal of Materials Science & Technology2023，，23： | 0 |
| 6 | Oxidation Performance and Interdiffusion Behaviour of two MCrAlY Coatings on a Fourth-Generation Single-Crystal Superalloy显示文摘The oxidation behaviour of a fourth-generation single-crystal superalloy without coating and with two types of MCrAlY coatings at 1140℃was studied.The results showed that both coatings greatly improved the oxidation resistance of the superalloy,and the addition of Hf further improved the oxidation resistance by pinning the oxide layer into the coating.Before and after oxidation,obvious Cr and Al interdiffusion was detected.Inward Cr diffusion induces the precipitation of a topologically close-packed phase,while the diffusion of Al affects the structure of theγ/γ’phase,the solubility of refractory elements,and the formation of an interdiffusion zone. | K.J.Tan J.J.Liang X.G.Wang X.P.Tao J.Gong C.Sun Y.Z.Zhou X.F.Sun | 2022 | Acta Metallurgica Sinica(English Letters)2022，35，4： | 0 |
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