Advanced Materials Research Vols. 146-147

Abstract: The analysis on ingredient and petrographic examination of 5mm thickness ANF-6 electroslag fluxes (70% CaF2 + 30% Al2O3) skin formed during 0.45C steel 260 kg ingot remelting by electroslag remelting furnace with 160 kW, Φ100 mm × 350 mm mould indicates that the lamination phenomenon of fluxes is observed, and the Al2O3 content in fluxes skin near mould side and near electroslag ingot side is higher 69.24%-75.62%, and the CaF2 content is 21.46%-28.36%, where at skin center 3 mm location, the Al2O3 content in fluxes skin is only 15.84% and the CaF2 content is 81.06%. The solidification mechanism of “ring shaped miniature fluxes pool” formed at upper edge of remelted ingot is advanced in this paper, and the surface quality of ingot by using large over-cooling and low melting-point fluxes is higher than that by using low over-cooling and high melting-point fluxes.

Abstract: Tribological behaviors and wear mechanism of bismaleimide resin and its composites modified by potassium titanate whiskers were investigated. The composites with outstanding tribological properties were prepared through several coupling agents and whisker contents under different friction loads. The incorporation of whiskers treated with silane into the matrix effectively improved wear properties and friction stability of the matrix, especially at severe friction condition as 30 kg. The wear volume of the neat resin at 15 kg and 30 kg friction load are 1.14 and 6.87 mm3, respectively. However, the wear volume of the composites containing 3 wt% potassium titanate whiskers at 15 kg and 30 kg friction load are 0.75 and 1.14 mm3, respectively. Furthermore, the addition of whiskers increased the ability to resist plastic deformation and crack of the matrix in a higher friction load.

Abstract: equal channel angular extrusion/Pressing (ECAE, ECAP) has the capability of producing ultra-fined grain (UFG) materials bellow the dimension of 1 μm. At present, it is one of the most important methods to get bulk UFG materials. In this paper, a systematic investigation of ECAP process on the pure Aluminum and die design is performed by using numerical simulation. The stress distributions on the die were obtained, and general consideration of the die during the whole pressing process was given. it was found that the closer the die corner is, the higher stress value results can be acquired. And the effective stress concentration in ECAP die cavity corner. The extruding load fell rapidly when the angular angle increasing. The proposed method can serve as preconditions to analyze the abrasion and fatigue of ECA Pressing die.

Abstract: Corrosion behavior in Zn and Zn-55Al baths were investigated on a Fe-based alloy, which was design to apply to hot-dip production lines as the anti-corrosion alloy. The results reveal that the Fe-based alloy shows excellent corrosion resistance both in pure zinc bath and Zn-55Al bath. And the reaction rate and intermetallic phase formation vary in different bath. In pure zinc bath, the intermetallic phases form on the Fe-base alloy is chiefly Fe-Zn phases contains Γ, δ and ζ phases. In Zn-55Al bath, the Fe-based alloy is comprised of Fe2Al5 and FeAl3 phases, and the outer layer is from bath itself. The more thickness the layer of Fe2Al5 phase, the more corrosion resistance of the alloy.

Abstract: This paper investigates the effect of minimum quantity lubricant (MQL) on the surface roughness of titanium alloy Ti-6Al-4V ELI when turning using uncoated tungsten carbide tool. The response surface method (RSM) design of experiment using Box-behnken was used to accomodate the turning experiment factors and levels. Turning parameters studied were cutting speed (100, 135, 170 m/min), feed rate (0.15, 0.2, 0.25 mm/rev) and depth of cut (0.6, 0.8, 1.0 mm). The results show that the feed rate was the most influence factor controlling the surface roughness produced. The feed rate (F) was found directly proportional with the surface roughness value (Ra) but inversely proportional to the cutting speed (Vc). MINITAB software was used to develop a surface roughness model, and the optimum condition was at 160 m/min of cutting speed, 0.18 mm/rev of feed rate and 1 mm of depth of cut. At the optimum condition low value of 1.54 μm surface roughness was obtained.

Abstract: TiO2–coated carbon felt (TCF) was prepared via a supercritical treatment with titanium tetraisopropoxide (TTIP) and different carbon felt as a precursor and support, respectively. The TCF samples with different carbon felts were characterized by X-ray diffraction, scanning electron microscopy, UV-VIS spectroscopy, particle size analyzer and BET surface area. The photocatalytic activities of samples were evaluated by congo red (CR) degradation. The result reveals that all the three samples show much higher photoactivity than the commercial P25. The activity order of the three samples is TCF1< TCF2 < TCF3. The photoactivity is strongly dependent on the surface area and the crystallite size: the larger the surface area and the smaller the crystallites, the higher the efficacy of photocatalytic degradation. The optimal photocatalytic condition is a CR concentration of 45 mg/l at pH 7.

Abstract: The Dynamic Mechanical Analysis (DMA) was applied to investigate the low frequency mechanical spectroscopy response of as-cast high damping Mg-3wt.%Ni hypoeutectic alloys. There are two peaks appearing on the temperature dependent damping spectrum (-100 - 420 °C). The broad peak P1 is overlapped by some small peaks due to the thermally activated dislocation movement, while the P2 peak is a solute grain boundary relaxation peak.

Abstract: Unlike the growth of crystal, the growth of icosahedral quasicrystal seems to have its own characteristics. Petal-like icosahedral quasicrystal grains (i-phase grains) morphology usually has been observed in as-solidified quasicrystalline alloys. The distinguished morphology is belonged to a given i-phase grains growth evolution mechanism. We first introduced a novel model named “coherent” model to illustrate i-phase grains growth evolution.

Abstract: The stress-strain curve in the large plastic deformation process is always not available due to the strain gauge deficiencies in large deformation measurement. Considering this problem, digital marker identification technique is used to measure large deformation of Steel Q235 with images taken by with charge-coupled device. Then together with the deformation measured by traditional stain gauge at small deformation stage, the total stress and strain curve is obtained at macroscale. The mesoscopic deformation is measured by a material testing system assembled with scanning electronic microscope. The images from the initial stage to the rupture stage are captured synchronously. What’s more, using the grid method, the strain and rotation in rational mechanics is analyzed.

Abstract: The thermodynamic analysis in Mg-SiO2 system was conducted for the determination of the priority reaction at experimental temperature. Then, Mg2Si reinforced Mg alloy was synthesized through reaction in Mg-SiO2 system at 730°C, whose Si mass fraction is up to approximately 10%. The thermodynamic analysis and microstructure investigation results show, that generation of reinforcing phase of Mg2Si in Mg alloy from the reaction in Mg-SiO2 system is feasible with lower free energy than that in Mg-Si at the same temperature; and under the experimental temperature and solidification condition, the microstructure of Mg-10Si alloy is composed of coarse primary Mg2Si dendrite crystal, Chinese script type eutectic Mg2Si, and α–Mg phase, the formation of α–Mg holes is resulted from the relatively high cooling rate leading to a deviation from the equilibrium diagram during solidification.