共查询到20条相似文献,搜索用时 15 毫秒
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AlON复相陶瓷的SHS-HIP工艺与显微结构 总被引:1,自引:0,他引:1
采用一种新的技术途径,合成A lON致密陶瓷.在100 MPa高压氮气气氛下,以铝粉、氧化铝为原料,采用燃烧合成热等静压工艺(SHS-H IP),制备出致密的A lON复相陶瓷.采用扫描电子显微镜和X射线衍射研究了产物的相组成、显微组织.研究表明,原料中A l2O3含量对产物形态、相组成及显微组织有着重要影响.当A l2O3含量为10%或20%时,产物具有振荡燃烧明显分层的特征;含量为30%或40%时,产物均匀致密.随着A l2O3含量的提高,产物中自由A l含量降低,A lON和A lN含量提高,产物变得更致密. 相似文献
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A closed cellular material containing polymers for intelligent materials has been developed. Polystyrene powder particles coated with a nickel–phosphorus alloy layer by electroless plating were sintered at high temperature. A metallic closed cellular material containing polystyrene was then fabricated. Scanning electron microscope indicated that polystyrene remains in the cells after heat treatment. The compressive tests of this material show a low Young’s modulus and high-energy absorption. These results indicate that this metallic closed cellular material can be used for the energy absorbing systems. 相似文献
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空心玻璃微珠表面化学镀Ni-P合金磁性涂层的研究 总被引:2,自引:0,他引:2
采用化学镀工艺在空心玻璃微珠表面包覆了一层磁性的Ni-P合金涂层,对其进行了表面金属化改性.分别用X射线衍射仪(XRD)、傅立叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)以及振动样品磁强计(VSM)对化学镀前后空心玻璃微珠的形貌、组成、结构以及磁性能进行了表征.结果表明:通过化学镀工艺制备的Ni-P合金涂层由原子团簇组成;涂层为非晶结构并具有较好的磁性能;化学镀后空心玻璃微珠的X射线衍射强度和红外透射强度均降低. 相似文献
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Equal channel angular pressing (ECAP) has been conducted on as-cast Mg-4.3 wt.%Zn-0.7 wt.%Y Mg alloy containing quasicrystal phase at a temperature of 623 K. After 8 ECAP passes, the grain size of the as-cast alloy is decreased from ∼ 120 to ∼ 3.5 μm, and the coarse eutectic quasicrystal phases are broken and dispersed in the alloy. Tensile testing has been performed on the ECAPed Mg-Zn-Y alloy at temperatures of 523 K and 623 K with initial strain rates from 1.5 × 10− 3 to 1.5 × 10− 4 s− 1. The ECAPed alloy exhibits a maximum elongation of about 600% when testing at 623 K using an initial strain rate of 1.5 × 10− 4 s− 1. Grain boundary sliding is considered to be the dominant deformation mechanism of the Mg-Zn-Y alloy in the temperature and strain-rate range investigated. 相似文献
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Diamond/Al composites were prepared by vacuum hot pressing (VHP) to get high thermal properties. The sintering temperature, pressure and time in the VHP process were optimized. Microstructures, thermal properties, interface reaction product and its effect on the properties of the composites were investigated. The result shows that the sintering temperature and time are key parameters to get high thermal property of the composites. The composites with 20–55 vol% diamond sintered at 650 °C for 90 min under a pressure of 67 MPa exhibit thermal conductivities of 320–567 W/mK, over 90% of the theoretical predictions by the differential effective medium (DEM) scheme. The high thermal conductivity is attributed to the favorable interface conductance, while the formation of aluminum carbide at diamond–Al interface is found to be negative. 相似文献
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R. Kaiser K. Williamson C. O’Brien S. Ramirez-Garcia 《Materials Science & Technology》2015,31(11):1298-1304
Investment cast biomedical alloys are often heat treated to refine the microstructure and improve mechanical properties. Test specimens of American Society for Testing and Materials F75 alloy (Co–28 wt-%Cr–6 wt-%Mo) were cast and solidified at two cooling rates, which influenced the size and area fraction of secondary phases (carbides) precipitated at grain boundaries and in interdendritic zones. The specimens were then subjected to hot isostatic pressing and age hardening. This produced smaller globular carbides of reduced area fraction, and reduced the size of micropores, independent of as cast characteristics. Strength and hardness were not significantly altered. The most significant effect of the post-casting treatment was to increase the ductility of the alloy, most likely due to the dissolution of brittle intergranular carbides and reduction in pore size. 相似文献
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Mamoru Nakamura Katsushi Kubo Shuzo Kanzaki Hideyo Tabata 《Journal of Materials Science》1987,22(4):1259-1264
The joining of hot-pressed silicon nitride ceramics, containing Al2O3 and Y2O3 as sintering aids, has been carried out in a nitrogen atmosphere. Uniaxial pressure was applied at high temperature during the joining process. Polyethylene was used as a joining agent. Joining strength was measured by four-point bending tests. The effects of joining conditions such as temperature (from 1400 to 1600°C), joining pressure (from 0.1 to 40 MPa), holding time (from 0.5 to 8 h) and surface roughness (R
max) of the joining couple (about 0.12, 0.22 and 1.2m) on the joining strength were examined. The joining strength was increased with increases in joining temperature, joining pressure and holding time. Larger surface roughness caused lower joining strength. The higher joining strength was attributed to a larger true contact area. The area was increased through plastic deformation of the joined couple at elevated temperatures. The highest joining strength attained was 567 MPa at room temperature, which was about half the value of the average flexural strength of the original body. The high temperature strength measured at 1200° C did not differ very much from the room-temperature value. 相似文献
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在单体与液晶相分离的过程以及单体固化的过程中施加交流电,得到液晶微滴尺寸和排列规则的PDLC膜。采用偏振红外光谱法对电场作用下液晶分子的重新取向进行了研究。结果表明:非工作状态下,液晶微滴的分子光轴处于无序态;工作状态下,分子光轴能够达到较高的有向度。 相似文献
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The pure NiAl intermetallic compound was fabricated by the combustion synthesis and hot pressing technique. Microstructure examination showed that the NiAl intermetallic compound contained fine grains. Analysis of the X-ray diffraction and the HRTEM studies showed that the phase in the intermetallics was the only NiAl phase. The NiAl showed prominent compression properties. The true ultimate compression strength and the fracture strain of the NiAl are 1002? 94+ 72 MPa and 21.6? 1.8+ 1.8%, respectively. The work-hardening capacity (Hc) is 1.40? 0.07+ 0.09 and the Vickers micro-hardness is 360? 19+ 15 HV. The finer grains, the high density dislocation and the seriously distorted lattices in the matrix, and the intense interactions between dislocations contribute to the prominent compression properties. 相似文献
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原位热压TiC/Ti/Al合成Ti2AlC的研究 总被引:1,自引:0,他引:1
以TiC/Ti/Al为原料,采用热压工艺在1400℃原位合成和烧结了含少量第二相Ti3AlC2的Ti2AlC材料.通过不同温度和不同热压时间下合成试样的XRD分析探讨了Ti2AlC的合成过程.结果表明,高温下Ti与Al反应生成中间相TiAl金属间化合物,然后TiC与TiAl金属间化合物反应生成Ti2AlC.初期反应非常迅速,大部分Ti2AlC在此阶段生成.反应后期反应物减少,速度变慢,同时生成少量第二相Ti3AlC2.不同温度下合成的Ti2AlC颗粒具有不同的形貌特征. 相似文献
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采用热压工艺制备了硅酸铝纤维/TCP生物功能梯度材料(FGM)。采用X射线衍射分析、扫描电镜、EDAX线扫描能谱分析、密度分析及洛氏硬度分析对FGM进行了研究,结果表明:纤维含量分布呈轴向对称梯度变化。FGM整体完好,无破损或裂纹出现。FGM在宏观上呈现较模糊的梯度分布,微观上则表现出成分的连续变化。TCP基体与纤维结合紧密。FGM中TCP与硅酸铝纤维及热压模之间均未发生化学反应生成杂质化合物,HA至TCP的相变是因为羟基磷灰石的分解产生。随纤维含量增加,FGM各梯度层的断裂形式由脆性断裂逐渐转变为韧性断裂,且韧性程度随纤维含量增加而增强。各梯度层硬度和相对密度随纤维含量的增加而提高,且在纤维含量为60 vol%时达到最高,分别为92.7 MPa和86.5%。 相似文献
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M. N. Rahaman R. E. Dutton S. L. Semiatin 《Materials Science and Engineering: A》2003,360(1-2):169-175
A method is described for the fabrication of dense thin sheets of γ titanium aluminide (γ-TiAl) by a powder metallurgy route involving hot isostatic pressing (HIP) of tape-cast monotapes. Gamma-TiAl powder (particle size <90 μm) was incorporated into a concentrated slurry by mixing with an organic binder in a solvent and the system was tape-cast to form sheets with a thickness of 400–600 μm. After insertion of the tape-cast sheet into a HIP can and binder removal in situ by thermal decomposition, HIP at 1100 °C under a pressure of 130 MPa produced dense sheets with a thickness of 250–400 μm. The free, dense sheets with a fine-grain microstructure were obtained by dissolution and oxidation of the HIP can. The carbon content of the fabricated sheets was 0.035 wt.%. Facile adaptation of the process to the production of γ-TiAl thin sheets with complex shapes is expected. 相似文献
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《Advanced Powder Technology》2021,32(10):3610-3623
Achieving the near-net shaping of brittle and difficult-to-machine materials is still challenging. Thus, we explore a method to prepare Ti-22Al-25Nb alloy by solid-powder hot isostatic pressing (HIP) diffusion bonding. The grain size, microstructure, interface features and mechanical properties of the fabricated alloy were systematically investigated. The results show that the solid-powder interface realizes a complete metallurgical bonding, and the grain size, composition and microstructure in transition zone is formed on the side of preform through recrystallization. There is a huge difference for the grain size between the powder forming zone and the preforming zone. As a result, the fabricated sample for solid-powder transition zone exhibits an excellent mechanical properties, with a tensile strength of 940 MPa, elongation of 2.9% and torsional strength of 815 MPa, respectively. In response to the torsional force, the crack starts from the preforming zone, and the crack deflection and branching occurs in the transition zone, thereby preventing the crack from propagating to the powder forming zone. The torsional strength of the solid powder HIP diffusion bonding zone is basically the same as that of the preformed zone. This study proposes a new solution for fabricating brittle and difficult-to-process materials and is of great significance in the development of the overall near-net shaping technology for complex components of such material. 相似文献
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Xiaolin Hong Bingchu Mei Jiaoqun Zhu Weibing Zhou 《Journal of Materials Science》2004,39(5):1589-1592
Polycrystalline Ti2AlC samples were synthesized by hot pressing of Ti, Al, TiC and active carbon powder mixtures. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used for phase identification and microstructure evaluation. No other phase except Ti2AlC was detected in samples synthesized by hot pressing of the 0.5TiC/1.5Ti/1.0Al/0.5C powder mixtures at 1400°C for 1 and 3 h under a pressure of 30 MPa. The densities of these two samples were 96.1 and 98% of the theoretical value of pure Ti2AlC, respectively. The reason that the densities of these two samples were lower than the theoretical density of pure Ti2AlC is that pore existed in these two samples. At lower temperature of 1300°C, the speed of the reaction forming Ti2AlC was slow. While at higher temperature of 1500°C, Ti2AlC transformed to Ti3AlC2. So these two temperatures are not suitable for the fabrication of Ti2AlC. 相似文献