排序方式: 共有148条查询结果,搜索用时 15 毫秒
1.
《Materials Science & Technology》2013,29(5):530-538
AbstractIn this study, an etching technique to detect the localised plastic deformation behaviour in a low carbon steel was developed. With this technique, etching with Fry solution under ultrasonic vibration was carried out on samples plastically deformed and then heated at 550°C for a certain period of time. The plastic zone was revealed by different degrees of etching in the plastically deformed and non-deformed regions; the plastic zone was found to be only slightly etched, whereas the other region was deeply etched. From the surface offset after etching, the deformation zone was found to be observable even at low magnification, such as 10 times. As the heating duration increased, the plastic zone became clearer. The mechanism for such an etching reaction is discussed on the basis of electrochemical analysis. 相似文献
2.
《Materials Science & Technology》2013,29(4):482-486
AbstractIn this paper, fundamental concepts of ultrasonics and characteristics of distinctive microstructures have been used to simply explain the effect of microstructure on the attenuation mechanism of ultrasonic waves in carbon steels. In addition, it has been shown that application of the second medium hardness instead of the bulk hardness is more appropriate to correlate the sound velocity and the microstructure. 相似文献
3.
《粉末冶金学》2013,56(1):99-104
AbstractThis paper reviews the mechanical and microstructural characteristics of hypoeutectoid steels obtained by powder technology, in which various carbonaceous petroleum products provide the carbon constituent. These steels are compared with others of similar composition obtained from graphite. 相似文献
4.
《Science & Technology of Welding & Joining》2013,18(2):236-243
AbstractThe high solidification cracking susceptibility of low C steel weld metals was investigated using pure Fe model alloys containing 0–0·23%C, 0–5%Ni and 0–0·0144%B. In addition, a few Fe–C–Ni ternary alloys were also tested. Solidification cracking susceptibility was tested using longitudinal varestraint and transvarestraint tests. Cracking was evaluated using crack length and brittleness temperature range criteria. The Fe–C alloys showed high cracking tendency in two regimes, the first in the ultralow carbon range of 0·03–0·05%C and the second in a narrow band close to 0·1%C. The cracking was much more than that attributable to solute segregation. In Fe–Ni and Fe–B alloys, cracking was a function of alloy content. Solidification cracking due to C and Ni was higher in the ferritic mode of solidification compared to the austenitic, unlike in stainless steels, where the ferritic mode provides high resistance to cracking. In Fe-C-Ni ternary alloys, cracking could be better related to composition in terms of a variable coefficient for C in the Ni equivalent. In the vicinity of 0·1%C, cracking was attributable to shrinkage due to solid state transformation from δ to γ in the brittle temperature range, and is similar to that occurring during continuous casting of steel. However, this factor did not appear to play a role in cracking in the ultralow C range of 0·03–0·05%C. 相似文献
5.
《International Heat Treatment & Surface Engineering》2013,7(3):121-124
AbstractThe poor tribological properties of zirconium limit its application, particularly its use in valves in the nuclear industry. Following up on a successful program to case harden titanium, the authors applied the same techniques to zirconium. Although the two metals are closely related, the diffusing species used for titanium were not found to be suitable for zirconium because of cracking in the sub-ceramic diffusion zone. A modified approach using hydrogen to improve the ductility of the layer successfully reduced its hardness, but not its propensity to cracking. 相似文献
6.
Jeff Olson Jeff Pan Jill Hochlowski Philip Searle Dave Blanchard 《Journal of The Association for Laboratory Automation》2002,7(4):69
Preparative Scale Supercritical Fluid Chromatography is emerging as a powerful alternative to HPLC for the purification and separation of complex chemical reaction mixtures. Advantages include greatly reduced solvent usage (and thus lower cost and environmental impact), higher throughput, and in some cases higher resolution. While there are commercially available prep SFC instruments, none currently offer all the features desired by many medicinal chemists engaged in the drug discovery process. These include: the ability to collect an unlimited number of fractions per sample with high recovery and negligible carryover, fully automated capacity to collect several hundred fractions, and the ability to collect fractions into the same disposable test tubes and racks which are already employed in HPLC. This article describes the customization of a preparatory scale SFC system purchased from Berger Instruments, Inc., Newark, DE. (a subsidiary Mettler-Toledo International, Inc., of Greifensee, Switzerland) in order to provide these capabilities. 相似文献
7.
《Journal of Adhesion Science and Technology》2013,27(10):1283-1306
The effect of surface chemistry and rugosity on the interfacial adhesion between Bisphenol-A Polycarbonate and a carbon fiber surface subjected to surface treatment to add surface oxygen groups was investigated. The surface oxygen content of PAN based intermediate modulus IM7 carbon fibers was varied by an oxidative surface treatment. The oxygen content of the carbon fiber surface increased from 4 to 22% by changing the degree of surface treatment from 0 to 400% of nominal commercial surface treatment levels. The oxidative surface treatment also causes an increase in surface roughness by creating pores and fissures in the surface by removing carbon from the regions between the graphite crystallites. To decouple the effects of surface roughness and the surface oxides on the interfacial adhesion, the oxidized fiber surface was passivated via hydrogenation at elevated temperature. Thermal hydrogenation removes the oxides on the surface without significantly altering the surface topography. The results of interfacial adhesion tests indicate that an increase in the oxygen content of the fiber does not increase the fiber-matrix interfacial adhesion significantly. Comparing adhesion results between oxidized and hydrogen passivated fibers shows that the effect of the surface roughness on the interfacial adhesion is also insignificant. Overall, dispersive interactions alone appear to be the primary factor in adhesion of carbon fibers to thermoplastic matrices in composites. 相似文献
8.
《Journal of Adhesion Science and Technology》2013,27(10):817-855
We have derived the equations which explicitly express the peak force, F max, and the apparent interfacial shear strength, τ app, measured in the pull-out and microbond tests, as functions of the embedded length. Three types of test geometries were considered: (1) a fiber embedded in a cylindrical block of the matrix material; (2) microbond test with spherical matrix droplets; and (3) pull-out test in which the matrix droplet had the shape of a hemisphere. Our equations include the local interfacial shear strength (IFSS), τ d, and the frictional interfacial stress, τ f, as parameters; the effect of specimen geometry appeared in the form of dependency of the effective fiber volume fraction on the embedded length. The values of τ d and τ f were determined by fitting our theoretical curves to experimental F max (l e) plots by using the least squares method. Our analysis showed how the local IFSS and the frictional interfacial stress affected the measured F max and τ app values. In particular, it was revealed that intervals of embedded lengths could exist in which frictional interfacial stress had no effect on F max and τ app, even if the τ f value was high. We also derived an equation relating the scatter in the interfacial strength parameters (τ d and τ f) to the scatter in τ app, which is experimentally measurable, and proposed a procedure to determine the standard deviations of τ d and τ f from experimental pull-out and/or microbond test data. 相似文献
9.
《Journal of Adhesion Science and Technology》2013,27(6):805-816
Amorphous silicon-containing diamond-like carbon (Si-DLC) coatings were deposited by Ar+ ion beam-assisted physical vapor deposition of tetraphenyl-tetramethyl-trisiloxane (704 Dow Corning diffusion pump oil) on AISI 4340 low alloy and 440° C high alloy steel specimens, as well as on thin wafers of the same compositions, in order to evaluate residual stresses within the coatings. During annealing in an argon atmosphere at 200°C for up to 30 min, the residual compressive stress, attributed to hydrogen entrapment during deposition, gradually changed to tensile due to loss of hydrogen, and the rate of stress increase decreased with increasing annealing time. The cohesion and adhesion failure loads of the coatings decreased with annealing time, as did the friction coefficient between the coating and a diamond stylus. The specific wear rate, measured by pin-on-disk tribometry, increased with annealing time. These properties are affected not only by the change in residual stress state during annealing, but most likely also by devitrification and the accompanying grain growth. If these effects are neglected, then the properties may be correlated directly with residual stresses in the coating. 相似文献
10.
《Journal of Adhesion Science and Technology》2013,27(10):999-1007
For bulk processing of carbon nanotubes, an important first step in adhesion to the nanotubes is often liquid-phase functionalization through chemical oxidation with acids (e.g., nitric and sulfuric), peroxides and/or potassium permanganate. In comparison, gas-phase photo-oxidation can be an alternative to introduce oxygenated functional groups on the surfaces of carbon nanotubes without the generation of liquid waste. In the present study, vacuum UV photo-oxidation of multi-walled carbon nanotube (MWNT) paper was investigated downstream from an Ar microwave plasma. X-ray Photoelectron Spectroscopy (XPS) was used to detect the carbon- and oxygen-containing functional groups in the top 2–5 nm of the sample's surface. The current results are compared to previous investigations using MWNT powder and single-walled carbon nanotube (SWNT) paper showing decreased levels of oxidation in MWNT samples. 相似文献