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991.
热压缩2091 Al-Li合金的流变应力行为 总被引:14,自引:0,他引:14
采用Gleble1500高温等温压缩试验研究了一种2091铝锂合金高温塑性变形时的流变应力行为。结果表明,应变速率和变形温度的变化影响合金稳态流变应力的大小,稳态流变应力与真应力大小无关。应变速率和流变应力之间满足双曲正弦关系,温度和流变应力之间满足Arhenius关系。可用包含Arhenius项的ZenerHollomon参数描述2091合金高温塑性变形时的流变应力行为。 相似文献
992.
在分析各种切换模型的基础上,针对实际应用的高低速模型切换存在的问题,提出了一种采用速度差对时间积分的模型切换方法.实验结果表明:采用上述控制策略的调速系统具有良好的静、动态性能. 相似文献
993.
G Frank J Qiu M Somsouk Y Weng L Somsouk JP Nolan B Shen 《Canadian Metallurgical Quarterly》1998,273(49):33064-33072
To assess the roles of the active site residues Glu160 and Asp181 of human FEN-1 nuclease in binding and catalysis of the flap DNA substrate and in vivo biological processes of DNA damage and repair, five different amino acids were replaced at each site through site-directed mutagenesis of the FEN-1 gene. The mutants were then expressed in Escherichia coli and purified using a His-tag. Even though the mutants bind to the flap DNA to different degrees, most of the mutants lost flap nuclease activity with the exception of an E160D mutant. This mutant retained wild type-like binding ability, specificity, and partial catalytic activity. Detailed steady state and pre-steady state kinetic analysis revealed that the functional deficiency of this mutant was due to retardation of the endonucleolytic cleavage. When the mutant enzyme E160D was expressed in yeast, it partially complements the biological functions of the homologous yeast gene, RAD27, and reverses the hyper-temperature lethality and hypersensitivity to methyl methanesulfonate, in a manner corresponding to the in vitro activity. 相似文献
994.
995.
为了提高微机过程控制系统的可靠性,保证长期稳定运行,对系统中可能出现的电网干扰、信号线干扰和地线干扰等进行了讨论,并提出了相应的软硬抗干扰措施. 相似文献
996.
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999.
A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe Cr Mn Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 069% in 18Cr18Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 081%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 μm. After homogenization of the hot rolled plate at 1 150 ℃×1 h followed by water quenching, the microstructure consisted of homogeneous austenite. 相似文献
1000.
H. B. Fan W. Zheng G. Y. Wang P. K. Liaw J. Shen 《Metallurgical and Materials Transactions A》2011,42(6):1524-1533
An Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glass with a diameter of 5 mm was prepared with the copper-mold-casting method. The corrosion resistance of
this amorphous steel in sulfuric-acid solutions was determined by electrochemical measurements. The passive film formed on
the surface of the alloy after immersion in the 0.5-mol/l H2SO4 solution for 1 week was analyzed by X-ray photoelectron spectroscopy (XPS). Electrochemical measurements show that the corrosion
resistance of the amorphous steel in the 1 mol/l-H2SO4 solution is superior to a stainless steel (SUS 321), and is almost the same as Ti6Al4V, which shows that the amorphous steel
has an excellent corrosion resistance in sulfuric-acid solutions. As the concentration of the sulfuric-acid solutions increases
from 0.5 mol/l to 4 mol/l, the corrosion resistance of the amorphous steel decreases. The XPS result reveals that a bilayer
structure of protective film formed on the surface of the amorphous steel in a H2SO4 solution. The compositions of the inner part of the film are MoO2, Cr2O3, CoO, and FeO, and those of the outer film are MoO3, Cr(OH)3, Co(OH)2, and Fe(OH)3. 相似文献