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811.
Kyung-Man Moon Hwang-Rae Cho Myung-Hoon Lee Sung-Kyu Shin Sung-Cheol Koh 《Metals and Materials International》2007,13(3):211-216
The differences between the general corrosion and microbiologically influenced corrosion (MIC) of steels were investigated
in terms of its electrochemical behavior and surface phenomena. The corrosion potential of steels in the absence of SRB (sulfate-reducing
bacteria) shifted to a negative value with the immersion time. However, the potential of the presence of SRB shifted to a
positive value after 30 days' incubation, indicating the growth of SRB biofilms on the test metal specimens and the formation
of corrosion products. In addition, the color of a medium inoculated with SRB changed from gray to black. The change in color
appeared to be caused by the formation of pyrites (FeS) as a corrosion product, while no significant change in color was observed
in a medium without SRB inoculation. Moreover, corrosion rates of various steels tested for MIC were higher compared to those
of steels in the absence of SRB. In particular, the corrosion current density of TMCP steels in the presence of SRB was larger
than that of other steels. Pitting corrosion was also observed at the surface of all steels in the SRB-inoculated medium.
The pitting corrosion likely occurred due to SRB that was associated with the increasing corrosion rates through increasing
cathodic reactions, which caused a reduction of sulfate to sulfide as well as the formation of an oxygen concentration cell. 相似文献
812.
Joon-Ho Shin Jong-Hwa Kim Ki-Won Kim Hyo-Jun Ahn 《Metals and Materials International》2002,8(4):417-422
Lead acid batteries have had restricted applications because of relatively low energy density below 50Wh/kg. Many efforts have achieved lighter battery components such as separators, connections and containers etc. Thus, the most important problem of the lead acid battery is to improve the low capacity of the active material in the positive electrode. The purpose of this study is to improve the utilization of the active material in the lead dioxide electrode for the lead acid battery through the production of lead oxide with better physicochemical characteristics through cementation. A cementation reaction was performed in 1.0wt.%HCl solution using pure magnesium plate as the reductant. We investigated the utilization of the active material and discharge characteristics of the positive electrode with a current density ranging from 3.4 to 108.8mAcm−2. As a result, the active material utilization was about 72% at 3.48 mAcm−2 and increased with decreasing current density. The discharge characteristics according to current density are especially very good at high current density 相似文献
813.
Youtao Xie Xuebin Zheng Xuanyong Liu Chuanxian Ding 《Journal of Thermal Spray Technology》2007,16(4):588-592
Titanium/dicalcium silicate composite coatings with different ratios (weight ratios as Ca2SiO4: Ti = 3:7, 5:5, 7:3) were prepared by plasma spraying. Effects of titanium addition on coating properties, such as bonding
strength, flexural modulus, and dissolution in simulated physiological environment, were studied. Results showed that the
bonding strength between coating and Ti-6Al-4V substrate increased with increase of titanium content in the composite coatings.
It was explained by the narrowed dissimilarity of thermal expansion coefficients between the coatings and substrates. Degradation
of mechanical properties after immersion in simulated body fluid was also studied. The dissolution of dicalcium silicate in
the composite coatings resulted in the decrease of flexural strength and flexural modulus of the coatings in the simulated
physiological environment. The higher titanium content in the composite coatings, the stabler are the composite coatings in
the physiological environment. 相似文献
814.
Grain coarsening tests were carried out on Al-4.5 pct Cu and Al-4.5 pct Si alloys. The effects of three variables, melt composition, pour temperature, and mold temperature, were determined. It was found that the macrostructure generally coarsened with increased pour and mold temperatures. Coarsening was extreme in the unrefined alloys but was retarded by the active grain refiners like titanium and columbium. The effect of boron was spectacular in suppressing coarsening tendencies. The results of the investigation support the carbide theory of nucleation as opposed to the peritectic theory. 相似文献
815.
Satyam S. Sahay B. V. Harish Kumar Sangeetha J. Krishnan 《Journal of Materials Engineering and Performance》2003,12(6):701-707
Design of industrial annealing cycles requires recrystallization and grain growth studies, which are typically carried out
under isothermal laboratory condition. The kinetics coefficients of these phase transformations are obtained from such studies,
which are subsequently used in designing the industrial nonisothermal cycles using the additivity principles. However, the
strong heating rate effects on the grain growth kinetics necessitate such kinetics studies using industrial thermal profiles.
In the present work, the hot and cold spot cycles of an industrial batch annealing cycle for AIK grade steel have been simulated
in a programmable laboratory furnace. Subsequently, the effect of annealing temperature, soaking time, and heating rate on
the microstructural features, such as grain size distribution, grain shape anisotropy, and grain orientation, have been investigated
through extensive quantitative microscopy. The implications of these results on the design of industrial batch annealing cycles
have been discussed. 相似文献
816.
Hualong Li Emilie Hsu Jerzy Szpunar Ravi Verma Jon. T. Carter 《Journal of Materials Engineering and Performance》2007,16(3):321-326
In order to determine the deformation modes in AZ31 magnesium alloy at room temperature, computer simulations of deformation
texture development and calculation of formability have been carried out. The simulation results were compared with the measured
texture results. Based on agreement between the experiments and simulations the active deformation modes were determined.
A Visco Plastic Self Consistent model was employed for the simulation of plastic deformation. Simulations and experiments
were performed for different initial textures. The goal of the study was to develop the understanding of deformation texture
evolution and its effects on mechanical properties of magnesium, with an ultimate goal of improving room temperature formability
of magnesium alloys.
This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati,
OH, October 15-19, 2006. 相似文献
817.
Gordon D. Gemmell Nicholas J. Grant 《JOM Journal of the Minerals, Metals and Materials Society》1957,9(4):417-423
The effects of solid solution alloying on the creep-rupture properties, deformation characteristics, ductility, and fracture of pure aluminum were studied by means of creep-rupture tests on polished specimens of three alloys each of Al-Cu (0.24, 0.79, and 2.05 pct Cu), Al-Zn (4.93, 9.89, and 19.78 pct Zn), and Al-Mg (0.94, 1.92, and 5.10 pct Mg) at 500°, 700°, and 900°F. 相似文献
818.
Bob R. Powell Vadim Rezhets Michael P. Balogh Richard A. Waldo 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):34-38
The micro structural analysis of die-cast AE42 reveals a correlation between micro structure and creep strength. A lamellar-phase
Al11RE3, which dominates the interdendritic microstructure of the alloy, partly decomposes above 150‡C into Al2RE and Al (forming Mg17Al12). The increased solubility of aluminum in magnesium at higher temperatures may also promote the decomposition of Al11RE3. The creep strength decreases sharply with these phase changes. A mechanism for the decrease in creep strength of AE42 is
proposed whereby the reduced presence of lamellar Al111RE3 and/or the presence of Mg17Al12 contribute to the observed poor creep strength at higher temperatures. 相似文献
819.
Nicholas J. Grant Earl C. Roberts John Chipman 《JOM Journal of the Minerals, Metals and Materials Society》1954,6(2):145-149
An equilibrium study was made of the distribution of chromium and oxygen between liquid iron, containing less than 1 pct Cr, and simple slags of the CaO(MgO)-SiO2-FeO-Cr2O3 type in the temperature range 1526° to 1734°C The effects of slag oxidation, temperature, and basicity were observed. 相似文献
820.
In the conventional metallothermic reduction (MR) process used to obtain tantalum powder in batch-type operation, it is difficult
to control the morphology and location of the tantalum deposits. In contrast, an electronically mediated reaction (EMR) process
is capable of overcoming this difficulty. It has the advantage of being a continuous process, but has the disadvantage of
a poor reduction yield. A process known as the MR-EMR combination process is able to overcome the shortcomings of the MR and
EMR processes. In this study, an MR-EMR combination process is applied to the production of tantalum powder via sodium reduction
of K2TaF7. In the MR-EMR combination process, the total charge passed through an external circuit and the average particle size (FSSS)
increase as the reduction temperature increases. In addition, the proportion of fine particles (−325 mesh) decreases as the
reduction temperature increasess. The tantalum yield improved from 65 to 74% as the reduction temperature increased. Taking
into account the charge, impurities, morphology, particle size and yield, a reduction temperature of 1123 K was found to be
optimum for the MR-EMR combination process. 相似文献