Materials Science Forum Vols. 704-705

Abstract: The isothermal section of the phase diagram of the ternary system Y–Fe–V at 773 K was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) techniques. It consists of 9 single-phase regions, 16 two-phase regions and 8 three-phase regions. The ternary compound YFe_12-xV_x (1.5≤x≤2.7, space group I4/mmm) with Mn₁₂Th-type structure was confirmed in this system. At 773 K, the maximum solid solubility of V in Fe, and YFe₂, is about 23 at.%, and 3 at.%, respectively, Fe in V is about 22 at.%. And that of Y in Fe, FeV and V don′t exceed 1 at.%.

Abstract: This research aims to provide theoretical proof for the further study on the factors of stress relaxation under different conditions. In this study, use Pinus sylvestris and dynamic stress-strain test system, though change temperature and moisture to research the stress relaxation of wood. The results showed that the temperature and moisture content on the stress relaxation have a significant impact. With temperature enhancing or moisture content rising, stress dramatically relaxation and residual stress rapidly decreased. In other words, the initial stress decreased gradually and the relaxation rate was rise. It was also found that, under same conditions, compared with the tangential section of the Pinus sylvestris, the radial section has larger initial stress and smaller stress relaxation rate. Besides, the initial stress of late wood is larger than early wood but the stress relaxation rate is smaller. Key words: Pinus sylvestris, tensile stress relaxation

Abstract: Xanthoceras Sorbifolia Bunge hull activated carbon (XSBHAC) developed by phosphoric acid activation for removing basic fuchsin (BF) has been investigated. Experiments were carried out as function of contact time, pH (4-10) and temperature (303,313 and 323K). Adsorption isotherms were modeled with the Langmuir and Freundlich isotherms. The data fitted well with the Langmuir isotherm. The Langmuir monolayer saturation capacities of BF adsorbed onto activated carbon were 351.35, 354.96 and 355.94 mg/g at 303,313, and 323 K, respectively.The kinetic models were also studied .The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation.Using the equilibrium concentration contents obtained at different temperatures, various thermodynamic parameters,such as △G,△H and △S, have been calculated. The thermodynamics parameters of system indicated spontaneous and endothermic process. Key words: Xanthoceras sorbifolia bunge hull;biosorption; basic fuchsin

Abstract: The electronic structure and elastic constants of arsenic doped β-SiC have been studied by first principles density functional theory (DFT) calculations. The band structure, bulk modulus, and density of states were calculated. We have demonstrated that both the top of the valence and the bottom of the conduction band shift to lower energy levels. However, arsenic doped β-SiC exhibits a non-monotonic variation of the band gap and bulk modulus with the concentration of As. Keywords: arsenic doped β-SiC, electronic structure, elastic constant, first principles

Abstract: Spark plasma sintering (SPS) technology was used in-situ to fabricate the Ti₂AlC/TiAl (Nb, B) composites. And the composites were treated by rapid heat treatment. which had many advantages, such as heating-up quickly, short holding time and relatively slow cooling. The hidden relationship between images could be reflected by Multi-fractal spectrum, which also could show irregularity apparently. In this paper, the SEM images which fabricated after rapid heat treatment were researched by multifractals. And the parameter was calculated by MATLAB through anglicizing the multi-fractal spectrum theory. There was only small fluctuate between lnχq (r) and lnr when r=0.00625, and lnχ_{q (r)} and lnr had well linear relationship in spite of the value of q. After the rapid heat treatment at T=1403 K, the correlation coefficient between τ (q) and q reached 99.99% . The trend of D (q) and q turned to be gently, and the fracture appeared uniformity, and these SEM images were single fractures. τ (q) and q show nonlinear relationship in q∈[-3,-1], and there was one observe steep.The clock shape relationship between the α and f (α) revealed good symmetry of spectrum, wider spectral width, uneven distribution of the fracture, multi-fractal feature clearly, and obvious characteristic of multi-fractal. Key words: multi-fractal spectrum, rapid heating heat treatment, fractal dimension

Abstract: The continuous rolling and sizing processes for producing non-quenching and non-tempering 36Mn2V steel pipes used in oil well were studied by the thermomechanical simulation test in this paper. The results showed clearly that the final microstructure was influenced by deformation temperature and stain applied. When continuous rolling temperature was controlled at 1050°C and strain at about 0.5 or above, dynamic recrystallization was completed and fine austenitic grain was obtained. When sizing temperature was controlled at 850°C or below and strain at about 0.2 or above, fine acicular ferrite was obtained with properties satisfying the requirement of the high quality pipe. The results of the study provided reliable data for the controlled rolling and sizing processes for the production of the 36Mn2V steel pipes.

Abstract: Developing a reliable engineering product requires huge amount of resources and knowledge. Often a huge amount of resources were wasted in trying to test products and understanding its reliability performances. Consequently, it takes obvious advantages of resources to develop a reliable engineering product using convenient and fast process in the fierce industrial competition. This paper optimized the structure of high voltage disconnector self-elastic contacts based on ANSYS Workbench. The parts are made of Cu-Cr alloy, the physical property is decided by the content of alloys, and the mechanical property is mainly decided by physical dimensions of self-elastic contacts which include section thickness, corner radius and middle groove width. The traditional design method for self-elastic contacts is tryout design which wastes huge amount of resources and knowledge and it is comparatively uneconomical. Using ANSYS workbench, the finite element model of the self-elastic contact was established, and the finite element analysis was carried out. Design spaces and sensitivity of the response variables, which were related to strength, stiffness and mass, were synthetically analyzed based on design of experiment and physical dimensions of self-elastic contact were optimized by the Optimizer DesignXplorer. After optimization, the self-elastic contact meets service conditions accurately, and the service life is evidently prolonged. Optimization results show that this structure optimization method based on ANSYS workbench is effective in the contact structure design and the capabilities to optimize multi-objective conflicting goals are highlighted. Keywords: Self-elastic contact; FEA; Optimization; ANSYS Workbench

Abstract: Activated carbons were prepared through chemical activation of lignin from straw pulping precursor using potassium carbonate as the chemical agent. Effects of activated temperature, K₂CO₃ /lignin ratio and the activated time on the yield, Iodine number of activated carbon were investigated. Experimental results indicated that the optimum conditions were as follow: activated temperature 800°C, K₃CO₃ (40% concentration) /lignin ratio 5: l, activated time 50min. These conditions allowed us to obtain a BET surface area of 1104 m2/g, including the external or non-microporous surface of 417 m²/g，Amount of methylene blue adsorption, Iodine number and the yield of activated carbon prepared under optimum conditions were 10.6mL/0.lg,1310 mg/g and 19.75%, respectively.

Abstract: This study proposes a numerical model of heat and moisture transfer based on volume averaging theory according to the internal heat and moisture transfer phenomena and different transfer mechanisms above the fiber saturation point (FSP). The model takes into account the process of phase change and assumes that the driving forces of free water and water vapor are the different pressure gradients. Keywords: Wood; Microwave drying; Heat and moisture transfer; Volume averaging theory

Abstract: Nickel-based filler metals are widely used in the nuclear power industry for overlay welding of austenitic stainless steel components. However, solidification cracking in the weld metal has been observed in a number of cases after the initial deposit of Alloy 52 filler metal on the 316L substrate. In this study, Alloy 52 and its 52M modification were employed to perform overlay welding on 316L specimens. With proper welding heat input, no solidification cracks were observed in the transition zone of both weld overlays. As the heat input increased, solidification cracks could be found in the welds but was found to a lesser extent in Alloy 52M overlays. Nevertheless, such cracks could be eliminated by applying 309L filler metal as a buffer. This could be related to lower S and P contents in the buffer layer to reduce solidification cracking susceptibility of the subsequent weld passes. Additionally, the results of spot Varestraint tests also indicated that Alloy 52M had better solidification and ductility-dip cracking resistances than Alloy 52.