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研究了SiCP / Ni 纳米复合材料的超塑性。SiCP / Ni 采用脉冲电沉积方法获得。拉伸实验温度为410 ℃和450 ℃, 应变速率范围为8.3 ×10 -4~ 5 ×10 -2 s -1 。温度为450 ℃、应变速率为1.67 ×10 -2 s-1时, 获得的最大延伸率为836 %。采用SEM、TEM 分析了沉积态材料的表面形貌、断口形貌及变形后的组织, 并对变形机理进行了探讨。通过SiC 颗粒稳定基体组织有利于实现材料的超塑性, 低空洞体积分数有助于获得大延伸率。晶粒长大到微米尺度时, 变形机制主要是位错协调的晶界滑移和位错滑移塑性。 相似文献
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研究了用电沉积方法制备的纳米Ni和Ni/SiCp纳米复合材料的超塑特性,在试验温度410℃和450℃,应变速率为8.3×10-4s-1~5×10-2s-1的条件下,纳米Ni和Ni/SiCp纳米复合材料均表现出超塑性.当温度为450℃、应变速率为1.67×10-2s-1时,在Ni/SiCp中获得最大延伸率为836%;在同样的温度下应变速率为1.67×10-3s-1时纳米Ni获得最大延伸率为550%.对超塑性变形后组织的分析表明,晶界滑移是主要变形机制,晶粒长大至亚微米/微米量级后,变形机制是位错协调晶界滑移和位错滑移塑性. 相似文献
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原位生成(TiBw+TiCp)/Ti复合材料的高应变速率超塑性 总被引:1,自引:1,他引:1
将纯钛粉和B4C粉按一定比例混合均匀后,通过反应热压方法原位合成制备了TiB晶须和TiC颗粒增强体积分数为3%的钛基复合材料,并在950℃以16∶1的挤压比对复合材料进行了高温热挤压变形.采用X射线衍射仪和扫描电镜分别研究了原位生成复合材料的相结构和微观组织,并在700℃以不同应变速率对钛基复合材料进行了高温拉伸变形.研究表明:纯钛和B4C在1200℃真空热压原位合成产生两种不同形状的增强体,即短纤维状TiB晶须和等轴状的TiC颗粒;应变速率为5.95×10-4、1.19×10-3s-1和0.89×10-2s-1时,(TiBw TiCp)/Ti复合材料都表现出超塑性,延伸率分别为205.43%、148.3%和112.85%;700℃变形时(TiBw TiCp)/Ti复合材料的应变速率敏感指数为0.45. 相似文献
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Ti-15-3钛合金超塑行为研究 总被引:2,自引:0,他引:2
为系统了解Ti-15-3合金的超塑性,研究了固溶态和两种不同变形量冷轧态的Ti-15-3合金板材在700~800 ℃和1×10-4 ~3×10-3s-1应变速率范围内的超塑性行为.结果表明:Ti-15-3合金具有较好的超塑性能,冷轧态合金的延伸率均优于固溶态,且随着板材冷轧变形量的增大而增大;各应变速率下,该合金都在780 ℃时获得最大延伸率和应变速率敏感性指数.在780 ℃和1×10-4s-1条件下拉伸时,冷轧变形量为52%的Ti-15-3合金板材获得了370%的延伸率,m值为O.56;变形温度和速率对合金的超塑性能影响很大,合金的延伸率在730~780 ℃范围内随温度的升高和应变速率的降低而升高,合金的流变应力则随之下降. 相似文献
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利用扫描电镜(SEM)和超塑性拉伸实验对一次热挤压加工成型的AZ61镁合金薄板(晶粒尺寸~12μm)超塑性变形特征进行了研究.结果显示,在最佳的变形温度(623K)和应变速率(1×10-4s-1)条件下,可获得的最大的超塑性形变量为920%.在523~673 K实验温度和1×10-2~1×10-5s-1应变速率范围内,材料的应变速率敏感指数(m值)随实验温度升高和应变速率的降低而增加.较高的m值(0.42~0.46)对应于晶界滑动机制(GBS),而较低的m值(0.22~0.25)则对应于位错滑移机制.变形温度和应变速率是影响超塑性变形量和变量机制的主要因素. 相似文献
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Nanocomposites of Al2O3/Ni–Co prepared using Al2O3 of various particle sizes were fabricated by pulse current electrodeposition. Their superplastic tensile deformation was investigated at strain rates of 8.33 × 10−4 s−1 and 1.67 × 10−3 s−1 and temperatures of 723–823 K. The Al2O3 particle sizes and the deformation temperature had significant influence on the elongation of the deposited materials. The optimal superplastic condition and the maximum elongation were determined. A low temperature superplasticity with elongation of 632% was achieved at a strain rate of 1.67 × 10−3 s−1 and 823 K. Scanning electron microscopy and transmission electron microscopy were used to examine the microstructures of the deposited and deformed samples. The grains grew to a micrometer dimensions and were elongated along the tensile direction after superplastic deformation. Superplasticity in electrodeposited nanocomposites is related to the presence of S at grain boundaries and to deformation twinning. 相似文献
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Z. C. Shao J. Guo Z. Zhao J. Xia M. Ma Y. Zhang 《Materials and Manufacturing Processes》2016,31(8):1004-1008
LiNi1/3Co1/3-xMn1/3O2 doped with Al2O3 (x = 0%, 2.5%, 5%, 10%) was synthesized by co-precipitation of Ni, Co, and Mn acetates. The influence of Al2O3 doping on structure and electrochemical performances of LiNi1/3Co1/3Mn1/3O2 was studied using X-ray diffraction (XRD) analysis, scanning electron microscopy, charge/discharge tester, and electrochemical workstation. It was found that the materials achieved the best electrochemical properties when x was 5%. The first discharge capacity was 156.3 mAh · g?1(0.1 C, 2.0–4.8 V), which was close to the un-doped sample (156.8 mAh · g?1). After 20 cycles, the capacity retention ratios at the C-ratios of 0.1C, 0.2C, and 0.5 C were 96.1%, 94.9%, and 89.4%, respectively, while the capacity retention ratios of the un-doped samples were only 92.6% (0.1 C), 91.8% (0.2 C), and 88.7% (0.5C). The alternating current impedance shows that the charge transfer in the electrode interface was the easiest when x was 5%. 相似文献
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ZhiJie Li JiDe Wang Zheng Xu YaHong Xie BenHui Wang 《Science and Technology of Advanced Materials》2013,14(7-8):566-570
Perovskite-type oxides BaCe0.90Sm0.10O3–δ (BCS) and BaCe0.80Gd0.10Sm0.10O3–δ (BCGS) were synthesized by the sol–gel method and characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Using the sintered samples as solid electrolytes and silver–palladium alloy as electrodes, ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in a solid-state proton-conducting cell reactor. The maximum rate of production of ammonia was 5.82 × 10–9 mols–1 cm–2. 相似文献
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Al2O3-TiC composite ceramic and W18Cr4V high speed steel were joined by diffusion bonding with a Ti-Cu-Ti multi-interlayer in a vacuum of 10−4-10−5 Pa. The interfacial microstructures of the Al2O3-TiC/W18Cr4V joint were investigated with optical microscope and scanning electron microscopy. The elemental concentration near the diffusion interface was evaluated by electron probe microanalysis. The results indicate that an obvious transition zone was formed between Al2O3-TiC and W18Cr4V during the vacuum diffusion bonding. The elements in the transition zone are mainly Ti and Cu with a small amount of Fe. Element Ti concentrates near the two interfaces of the Al2O3-TiC/transition zone/W18Cr4V. The microhardness of the transition zone is lower than that of Al2O3-TiC and higher than that of W18Cr4V. The formation process of the transition zone consists of five stages: (i) Formation of Cu-Ti liquid phase; (ii) Full melt of Cu; (iii) Full melt of Ti; (iv) Formation of reaction layer; (v) Formation of Cu-Ti solid solution and increment of reaction layer. 相似文献
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Bualan KhumpaitoolJinda Khemprasit 《Materials Letters》2011,65(6):1053-1056
Li0.30Cr0.02Ni0.68O giant dielectric ceramics doped with Al2O3 were prepared by solid-state reaction via sol-gel process. The sintered samples were characterized using X-ray powder diffraction and scanning electron microscopy, and dielectric properties were also investigated. All doped samples showed the single phase of cubic rock-salt structure NiO. With increasing Al2O3 content, the crystallite size and grain size decreased, possibly due to an occurrence of the secondary phases at grain boundaries which inhibit the grain growth. The sample with 0.2 wt.% Al2O3 showed nearly 7 times lower tanδ (2.37) and higher εr (7.25 × 106) measured at 1 kHz and room temperature when compared to the pure sample. 相似文献
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《Materials Science & Technology》2013,29(3):378-382
AbstractIn the present work, alumina and diopside were introduced in hydroxyapatite matrix, and hydroxyapatite/Al2O3/diopside ceramic composites with good mechanical properties were fabricated by uniaxial hot pressing. The behaviours of hydroxyapatite/Al2O3/diopside ceramic composites in simulated body fluid were studied by SEM, Fourier transform infrared spectroscopy and electron probe microanalyser. Scanning electron microscopy images showed an obvious mineral layer formed on the soaked composite surface, which indicated that the introduction of Al2O3 and diopside in hydroxyapatite matrix could not only improve the strength and toughness of the composites but also maintain its ability to precipitate an apatite layer. 相似文献
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S N Vaidya 《Bulletin of Materials Science》1999,22(3):287-293
We report first observation of new polymorphs of Al2O3 and Fe2O3 in specimens of xerogelγ Al2O3 andγ Fe2O3 quenched from high pressures and temperatures. At about 5 GPa and 1400°C, xerogel gamma alumina (XGA) transformed into a
polymorphic mixture of phasesα Al2O3, B Al2O3 and C Al2O3, while XGA containing 1 wt% Cr2O3 transformed into a mixture of phasesαAl2O3, H Al2O3 and k′ Al2O3. The phases B Al2O3, C Al2O3 and H Al2O3 have the monoclinic-, cubic- and hexagonal-rare earth sequioxide (Ln2O3) type structure, respectively. At 5·2 GPa and 1450°C, XGA yielded a mixture ofα Al2O3 and hexagonalμ Al2O3. At STP, the phaseμ Al2O3 was found to transform to another hexagonal phaseλAl2O3 over a 10 week period.
At 5·2 GPa and 900°C,γ Fe2O3 showed transition to a new phase H Fe2O3 which probably has an 8 layer close packed structure. In nanocrystalline TiO2, only the anatase to rutile transition was found. The results are discussed using the free energy vs temperature diagram
for xerogel and nanocrystalline materials. 相似文献
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利用扫描电镜、原子力显微镜、恒电位脉冲等研究了2205双相不锈钢在中性含Cl-环境下氧化物引起点蚀萌生的机理。实验发现MgO-Al_2O_3系夹杂物中MgO偏聚处以及MgO-Al_2O_3-CaO系夹杂物中CaO富集处会引起夹杂物处基体同周围基体接触电势差增加。此外,CaO富集处易使夹杂物表面出现显微缝隙并使基体裸露,产生亚稳态蚀坑。经Ce处理后发现夹杂物成分变为含Ce_2O_3·11Al_2O_3或Ce_2O_3·Al_2O_3为主的复合夹杂,夹杂物与基体接触电势差减小并且在含Ce_2O_3复合夹杂物处未发现点蚀萌生现象,最后阐述了非金属氧化物引起点蚀的机理以及Ce与氧化物反应的机制。 相似文献
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This study investigated the photocatalytic behavior of the coupling of TiO2 with phosphorescent materials. A TiO2 thin film was deposited on CaAl2O4:Eu2+,Nd3+ phosphor particles by using atomic layer deposition (ALD), and its photocatalytic reaction was investigated by the photobleaching of an aqueous solution of methylene-blue (MB) under visible light irradiation. To clarify the mechanism of the TiO2-phosphorescent materials, two different samples of TiO2-coated phosphor and TiO2–Al2O3-coated phosphor particles were prepared. The photocatalytic mechanisms of the ALD TiO2-coated phosphor powders were different from those of the pure TiO2 and TiO2–Al2O3-coated phosphor. The absorbance in a solution of the ALD TiO2-coated phosphor decreased much faster than that of pure TiO2 under visible irradiation. In addition, the ALD TiO2-coated phosphor showed moderately higher photocatalytic degradation of MB solution than the TiO2–Al2O3-coated phosphor did. The TiO2-coated phosphorescent materials were characterized by transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photon spectroscopy (XPS). 相似文献
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D. B. Lee S. H. Kim K. Niinobe C. W. Yang M. Nakamura 《Materials Science and Engineering: A》2000,290(1-2)
Three kinds of L12-type Al3Ti–Cr alloys, Al67Ti25Cr8, Al66Ti24Cr10 and Al59Ti26Cr15, were prepared by induction melting followed by thermomechanical treatment. The oxidation behavior was investigated at 1273, 1373 and 1473 K in air. The oxidation resistance of the prepared alloys was excellent, however, there were some differences for each alloy. The isothermal oxidation resistance increased in the order of Al59Ti26Cr15, Al66Ti24Cr10 and Al67Ti25Cr8, while the order became reversed in terms of the cyclic oxidation resistance. As more Al2O3 formed owing to the increased Al content in the alloy, the isothermal oxidation resistance increased, whereas the cyclic oxidation resistance decreased. The oxide scale was primarily composed of Al2O3, contaminated with Cr2O3 and TiO2 that were present mainly at the lower part the oxide scale. 相似文献