Advanced Materials Research Vols. 146-147

Abstract: The experiment studied the influence of slag system on nitrogen content in high nitrogen steels which refined by the method of high-pressure and bottom-blowing nitrogen under the conditions of 1.0Mpa. The results shows that nitrogen content are up to 1.0% without the over of slag, and after adding slag, nitrogen content are up to 1.39%; Alkalinity of protecting slag has little effect on the nitrogen content, however, there are very effective to increase nitrogen after using CaF2 instead of SiO2 ,and its nitrogen content are as high as 1.48%; the effect of increasing nitrogen are clear by adding no more than 0.5% pure aluminum, but when aluminum content are more than 0.5%, the nitrogen content in steel are not change significantly, meanwhile, if adding CaF2 slag system, it will be more effective increase nitrogen than only adding pure aluminum.

Abstract: The composite coatings were prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) plus cathodic electrophoretic deposition (E-coat) to improve corrosion protection. SEM observation revealed that the organic layer was integrated with PEO film by physically interlocking; Potentiodynamic polarization(E-i) measurements in 3.5% NaCl solution, copper accelerated acetate salt spray(CASS) test and immersion test were employed to evaluate corrosion principle and corrosion rate of composite coatings. It is indicated that the corrosion resistance of composite coatings was improved obviously compared to the PEO film. There is no noticeable pitting corrosion on the composite coatings after 320h CASS test. The adhesion of composite coatings was evaluated by cross-cut and pull-off test. The results show that adhesion of composite coatings can reach to level 0 and 11.3 N/mm2 as a result of the blocking effect between organic layer and PEO film.

Abstract: The hydraulic steel structure is an important device in water resources and hydropower engineering, affected by operating environment, corrosion is becoming an important factor in affecting the structure on safe operation .In this paper, fuzzy assessment method for disaster degree identification is introduced, using the Monte-Carle numerical simulation for distance measurement to achieve the distance measurement calculated of corrosion morphology, making corrosion assessment of hydraulic steel gate quantitative. Combining with the study for attenuation of mechanical properties of corrosion components, this paper propose the method of quantitative correction of corrosion components based on five levels, clearing the impact properties of corrosion components caused by corrosion morphology .

Abstract: Friction and wear properties of SiC and immerse copper graphite(C/Cu) against stainless steel (1Cr18Ni9Ti) friction couples were studied under room temperature and unlubrication by pin-disc tribometer. The test shows that at sliding speed of 0.56ms-1 and normal load of 5N, 20N, the SiC/1Cr18Ni9Ti friction coefficient decreases. The immerse copper graphite shows good friction and wear behavior at load 50N, at which the copper of graphite matrix is transported to the surface from the pore of graphite matrix to form a couple of copper and copper. It is difficulties to measure volume loss. When load increased, the copper was transported to generate the film and was grinded away continuously, which the immerse copper graphite(C/Cu) volume loss increases at load 120N. The results of comparing two couples show volume loss of the couple SiC/1Cr18Ni9Ti is severe, so it is not suitable to combine a couple. The couple of immerse copper graphite (C/Cu)/1Cr18Ni9Ti is better applied at low load.

Abstract: DSC measurements have been carried out for the as-quenched xNa2O- (15-x)Li2O-4B2O3-11Al2O3-5BaO-65P2O5 (x=0,3.75,7.5,11.25 and 15 mol%) glasses with different particle size. Two crystallization peaks appear on the DSC curves for sample sized 90-110μm. The presence of two crystallization peaks is due to different crystallization mechanisms, surface and bulk (internal) crystallization. The X-ray diffraction measurements are also employed to investigate the crystallization of glasses. The results show that bulk crystallization is difficult to occur in the studied phosphate glasses. The effect of mixed alkali on glass thermal stability is also studied in this paper. The surface and bulk crystallization active energies are calculated according to Kissinger equation.

Abstract: A series of room temperature ionic liquids bearing hydroxyl groups, namely 1-(3’-hydroxyl-n-propyl)-3-alkylimidazolium tetrafluoroborate or hexafluorophosphate, were prepared and characterized. Their typical physical properties were also determined. The tribological test results show that these ionic liquids possess better friction-reducing and anti-wear ability for aluminum-on-steel system than lubricant X-1P. The friction coefficients of them are little higher than that of the nonfunctionlized ionic liquid LP308, while they possess better anti-wear abilities than the latter, which may ascribe to the chemical activity of hydroxyl group. Both the anions and the side substituted alkyl chains attached to the imidazolium cations affect the tribological performance of the lubricants. The SEM, EDS and XPS analysis of the worn surfaces show that complicated tribo-chemical reactions were involved in the sliding process. The boundary films composed of fluorides, nitrogen oxide, BN, and FePO4 were generated on the rubbing aluminum surfaces, which contribute to effectively decreasing the friction and wear of the contacts.

Abstract: It is well known that structural behaviors of composite solids are determined by topology of microstructures of different sizes. In this paper a concurrent topology optimization method for integrated design of materials and structures with periodical microstructure was presented. The microstructures were assumed to be uniform in macro scale and heterogeneous in micro scale and the optimization object was to maximize the material fundamental frequency. Design variables for structure and material microstructures were defined, independently. RAMP (Rational Approximation ofMaterial Properties) was adopted to ensure clear topologies in both macro and micro scales. Design variables for structure and material microstructures were integrated into one system by using the super-element method. Influences of Representative Volume Element sizes, the microstructure configuration and macro arrangement are investigated. Numerical experiments validate the proposed method which can be used as an innovative design concept for the lightweight structures.

Abstract: CH3SiCl3-H2-Ar system was adopted to prepare SiC Filament of high tensile strength by high-frequency induction during Chemical Vapor Deposition (CVD) method. Room-temperature tensile strength of SiC filament prepared under different temperature was test. Crystal structure, surface morphology and fracture character of SiC filament was analyzed with “X-ray diffractometer and scanning electron microscope. Influence of temperature to final tensile behavior of SiC filament was discussed synthetically. The result shows that tensile strength is very sensitive to temperature. From 1000°C to 1400°C, tensile strength increases and then decreases as temperature increases. At 1200°C, tensile strength reaches its max value, the reason ofwhich is composed of three parts. The first one is that the deposited product is β-SiC. The second one is that surface of SiC filament is smooth. The third one is that fracture surface shows ductile dimples fracture, brittle fracture and cleavage fracture patterns. 1200°Cis considered as one reasonable temperature in our laboratory to prepare SiC filament.

Abstract: The microstructure especially the size, shape, number and distribution of precipitate, together with the strain hardening exponent n value at different strain range during plastic deformation of the Al-0.9Mg-1.0Si-0.7Cu-0.6Mn alloy sheet, subjected to different heat treatment were investigated. The results showed that the strain hardening exponent n values of Al-0.9Mg-1.0Si-0.7Cu-0.6Mn alloy sheet at any different strain range are different from each other, which is in agreement with the result that the relationship between true strain and true stress of polycrystalline alloy sheet during tensile test does not fully meet the Hollomon formula. The continuous strain hardening exponent nc defined in this paper essentially represents the approximate liner strain hardening effect during the total calculating strain range, while the stage strain hardening exponent ns defined in the paper can objectively indicate the counteraction of the micro strain hardening with the micro strain softening of alloy sheet during plastic deforming. When the precipitate in the matrix of alloy sheet can be cut by dislocation, the alloy sheet has the weakest strain hardening effect at the beginning of yielding process. Otherwise, the alloy sheet has the most prominent strain hardening effect at the beginning of yielding process when the precipitate in the matrix can be bowed bypass operation of dislocation. Gridded precipites is of no advantage to the glide and multiplication of dislocation of alloy sheet.

Abstract: Magnesium alloys are potential in biomedical materials, but their corrosion rates are high in human body fluid so that they can not be used enough time. Therefore, to improve the anti-corrosion property of the alloys is important for their application in biomedical materials. In the work, a new coating was prepared from poly (3-hydroxybutyrate) (PHB), a biopolymer used as a sustained release carrier of drugs. The effect of the PHB coating was studied by electrochemical tests, scanning electron microscope (SEM) and weight loss corresponding with the corrosion time. The result showed the sample coating PHB have a higher corrosion potential than one before coating PHB, that is, PHB coating is effective for improvement of corrosion resistant of the alloy. Moreover, the corrosion state on the surface is even by SEM, implied the corrosion rate of the PHB coating is divinable and controllable. Whereby, PHB should be suitable for anti-corrosion of magnesium alloys applying in biomedical materials.