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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.
因瓦合金异质材料焊接工艺的研究 总被引:1,自引:0,他引:1
研究了因瓦合金异质材料焊接工艺,通过试验选择了理想的异质焊接材料EZNiFe-1,并且对其焊缝进行了力学性能试验,并制定了合理的焊接方案,最终成功地保证了焊缝的低膨胀特性. 相似文献
993.
994.
用机械合金化方法制备Ni-Al系金属间化合物 总被引:6,自引:0,他引:6
用球磨机分别对Ni-50at.-%Al和Ni-25at.-%Al混合粉末进行机械合金化,并对Ni_3Al预合金粉末进行高能球磨,观察了粉末的金相组织,测定了粉末的硬度、平均直径和晶粒尺寸,并作了XRD物相分析结果表明,经3h研磨,Ni-50at.-%Al混合粉末变成NiAl金属间化合物,其晶粒直径约5nm;经5h机械球磨,Ni-25at.-%Al混合粉末成为无序的亚稳定Ni固溶体,而Ni_3Al预合金粉末由Ll_2型长程有序金属间化合物转变为fcc无序固溶体;球磨更长时间,则形成纳米晶. 相似文献
995.
Ni-base solid solution (γ) toughened Mo2Ni3Si metal silicide “in situ” composites were fabricated with different volume fraction of Mo2Ni3Si primary dendrite uniformly distributed in irregular Mo2Ni3Si/γ eutectic matrix. Results of room-temperature dry sliding wear tests indicated that the composite with a medium volume fraction of primary Mo2Ni3Si phase possessed the best wear resistance by optimum combination of the unique mechanical property of Laves phase Mo2Ni3Si and toughening effect of ductile γ phase. The primary wear mechanism is microplowing and soft-abrasion of the interdendritic Mo2Ni3Si/γ and subsequent brittle fracture of the hard Mo2Ni3Si primary dendrites. Ductile γ phase provided good toughening effect to Mo2Ni3Si Laves phase during dry sliding wear process. 相似文献
996.
FANXin-min HuiJing Yinsheng 《材料热处理学报》2004,25(5):635-637
The low carbon microalloy steel samples were heated to different temperatures by high voltage electropulse discharge heating method. The temperature of sample increases with the discharge current density. Microstructures were observed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that coexist microstructure of ultrafine ferrite grain and martensite can be obtained by proper high voltage electropulse discharge heating process parameter. The tensile testing indicate that better mechanical properties were obtained, including 758MPa yield strength, 796MPa ultimate strength and 12% total elongation. 相似文献
997.
998.
L. Bartosiewicz I. Singh F. A. Alberts A. R. Krause S. K. Putatunda 《Journal of Materials Engineering and Performance》1995,4(1):90-101
An investigation was carried out to examine the influence of microstructure and chromium on the tensile properties and plane
strain fracture toughness of austempered ductile cast iron (ADI). The investigation also examined the growth kinetics of ferrite
in these alloys. Compact tension and round cylindrical tensile specimens were prepared from ductile cast iron with Cr as well
as without Cr. These specimens were then given four different heat treatments to produce four different microstructures. Tensile
tests and fracture toughness tests were carried out as per ASTM standards E-8 and E-399. The crack growth mechanism during
fracture toughness tests was also determined.
The test results indicate that yield strength, tensile strength, and fracture toughness of ADI increases with an increase
in the volume fractions of ferrite, and the fracture toughness reaches a peak when the volume fractions of the ferrite are
approximately 60% in these alloys. The Cr addition was found to reduce the fracture toughness of ADI at lower hardness levels
(<40 HRC); at higher hardness levels (≥40 HRC), the effect of chromium on the fracture toughness was negligible. The crack
growth mechanism was found to be a combination of quasi-cleavage and microvoid coalescences, and the crack trajectories connect
the graphite nodules along the way. 相似文献
999.
1000.
Spoke-like ZnO nanoneedles have been successfully synthesized at the ambient pressure through thermally oxidizing Zn powders containing Au nanoparticles. X-ray diffraction analysis indicates that the ZnO nanoneedles have a hexagonal wurtzite structure of the crystalline ZnO. The morphology of the products was examined by FESEM. The photoluminescenee(PL) spectrum under 325 nm exhibits both an UV emission and a green emission. It is interesting to note that the heating rate plays a key role in the synthesis of ZnO nanoneedles. Based on this discovery we propose to explain the special growth behavior as novel mechanism that a large temperature gradient and Au nanoparticles simultaneously result in the spoke-like ZnO nanoneedles growth. 相似文献