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991.
C. Cagran B. Wilthan G. Pottlacher B. Roebuck M. Wickins R. A. Harding 《Intermetallics》2003,11(11-12):1327
The families of titanium aluminide intermetallic alloys have attractive high temperature mechanical properties which make them potential candidate materials for a wide range of applications, particularly in the aeronautic and automobile sectors. The development of appropriate manufacturing techniques is an essential stage in the engineering exploitation of these materials, e.g., Induction Skull Melting is one of the techniques which needs to be optimised for the casting of titanium aluminides. Research is underway to develop a computer model of this process but data are required for the key thermophysical properties. Pulse-heating techniques have been used to measure properties for the Ti–44Al–8Nb–1B system. Rectangular samples have been prepared and are resistively heated as part of a fast capacitor discharge circuit. Time-resolved measurements with sub-μs resolution of currents through the specimen were made with a Pearson probe current monitor using the induction principle. Voltages across the specimen were determined with knife-edge contacts and voltage dividers, and radiance temperatures of the sample were measured with a pyrometer. These measurements allow the calculation of specific heat and dependencies between enthalpy, electrical resistivity and temperature of the alloy up into the liquid phase. Data for thermal diffusivity have been obtained by using the Wiedeman–Franz relation. The results are compared with those obtained using DSC and the four-probe method to measure the temperature dependence of the resistivity. 相似文献
992.
2005年上半年,我国共生产海绵钛3801.6t,同比增长68%;生产钛粉342.5t,同比减少了76.5t;生产钛加工材5033.9t,同比增加了17%。2005年上半年,我国海绵钛进口量大幅减少,仅642t,钛加工材却大幅增加,达3024t。尽管从2004年开始,海绵钛及钛加工材价格大幅t涨,但我国对海绵钛和加工材的需求乃明显上升,预计2005年我国海绵钛的需求在万吨左右,而实际产量估计达到9000t左右,与实际需求稍有差距。世界海绵钛的生产能力不断扩大,预计2005年全球海绵钛的供应能力将增加23%,下半年海绵钛价格将趋于平稳。 相似文献
993.
介绍了一种将分型线隐藏在非可视面的汽车外饰塑件注射模的基本结构。这一结构已广泛应用在国外中高档轿车的保险杠、防擦条等零件的成型模具上,从内分型线模具的定义、设计概念——同步推出、基本结构——变角度导轨、动作要点等方面对新型模具结构进行了阐述。 相似文献
994.
采用共混法制备聚乙烯/镁铝水滑石纳米复合材料。XRD、SEM、TEM和性能测试表明:镁铝水滑石纳米晶体分散在聚乙烯基体中,且有少部分发生插层;阴离子表面活性剂对水滑石的处理效果要优于偶联剂;pH值对处理效果有一定影响;镁铝水滑石阻燃剂填充聚乙烯体系阻燃效果,要优于填充A1(OH)3阻燃剂。 相似文献
995.
录音机零件级进模设计 总被引:1,自引:1,他引:1
通过对录音杌零件的冲压工艺性分析,介绍了确定生产该零件采用的级进模模具结构和零件排样图的过程,而且解决了同一零件上向上和向下两个不同方向弯曲。 相似文献
996.
Solid-solution hardening and softening by Fe additions to NiAl 总被引:3,自引:0,他引:3
Solid-solution hardening in the case of a ternary alloy addition to a B2 compound with the triple defect structure has been investigated. The fact that the ternary element may occupy either of two sublattices or may affect the concentration of other types of point defects present in the material makes this a very interesting problem to consider. Ni-rich (40 at% Al), stoichiometric (50 at% Al), and Al-rich (52 at% Al) alloys were doped with up to 12 at% Fe. Lattice parameter, bulk density and hardness measurements were performed on samples quenched from 1000 °C. It was found that solid-solution softening actually occurs in the Ni-rich alloys, while hardening was observed in the stoichiometric and Al-rich alloys. The vacancy concentration was determined from the experimental data, and the site occupancies of the Fe atoms were estimated from a thermodynamic model. Through careful consideration of all point defect concentrations the solid-solution hardening and softening behaviors could be effectively rationalized. 相似文献
997.
998.
Sodium sulfate: Deposition and dissolution of silica 总被引:1,自引:0,他引:1
Nathan S. Jacobson 《Oxidation of Metals》1989,31(1-2):91-103
The hot-corrosion process for SiO2-protected materials involves deposition of Na2SO4 and dissolution of the protective SiO2
scale. Dew points for Na
2SO4 deposition are calculated as a function of pressure, sodium content, and sulfur content. Expected dissolution regimes for SiO2 are calculated as a function of Na2SO4 basicity, hence
generated by fuels with 0.5% and 0.05% S. Controlled-condition burner-rig tests on quartz verify some of these predicted dissolution regimes. However, the basicity of Na2SO4 is not always a simple function of
(Na2O) show that carbon creates basic conditions in Na2SO4, which explains the extensive corrosion of SiO2-protected materials containing carbon, such as SiC. 相似文献
999.
1000.
Key experiments were carried out on the three Al–R–Mg (R=Gd,Dy,Ho) systems and the results obtained used for the thermodynamic optimisation reported in a separate paper in this issue [Caccasmani G, De Negri S, Saccone A, Ferro R. Intermetallics this issue.]. The samples were characterized by differential thermal analysis (DTA), X-ray powder diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM) and quantitative electron probe microanalysis (EPMA). The isothermal sections at 400 °C are all characterized by extended homogeneity regions at a constant rare earth content. The extension of the (Mg,Al)R solid solution, cP2-CsCl type, varies with the R atomic number. Ternary compounds (τ) of Al2(R,Mg) stoichiometry (hexagonal Laves phases with MgNi2-type structure) have been found to exist at 400 °C in all the systems. Their temperatures of formation were detected by DTA measurements. 相似文献