Advanced Materials Research Vols. 641-642

Abstract: In this paper, B-Ni-Al shield materials were fabricated by vacuum metal infiltration. The B-Ni-Al Composite were fabricated by preheating BN+Ni at 1550°C for one hour before infiltrating Al alloys into the preforms in a vacuum at 1100°C for two hours. Microstructural characterization of the materials obtained was performed using X-ray diffraction, scanning electron microscopy(SEM). Mechanical properties were evaluated by fracture toughness and bending strength. AlN was produced with interfacial reactions between Al and BN.

Abstract: In this study, porous architectures with controllable morphologies on Aluminum foils were fabricated by a simple solution method using zinc nitrate hexahydrate and hexamethylenetetramine as reactants. Unlike works reported previously, we show that the porous architectures on the surface of Aluminum foils can be adjusted by controlling the molar ratio and total concentration of reactants, which is proved to be of importance in tailoring the wettability of the surface. It is found that by adjusting the space of pores and the thickness of nanoslices, the water contact angle of the obtained surface can change from hydrophobic to superhydrophobic.

Abstract: Low cycle fatigue failure tests of the powder metallurgical nickel based superalloy FGH96 at 550°C and 720°C were carried out under total strain-controlled mode (R=-1). The fatigue failure behaviors were investigated by analyzing cyclic stress response and observing microstructure after fatigue through scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show that FGH96 superalloy exhibits cyclic stability at 550°C, and cyclic softening afterwards at 720°C with Δε/2=0.4% , and of cyclic softening at 720°C with Δε/2=0.7%. After high temperature low cycle fatigue, the γ′ precipitates are cuboidal for all samples. No coarsening of γ′ precipitates was detected at 550°C and at 720°C with Δε/2=0.4%, but small γ′ precipitates get together to be larger precipitates at 720°C with Δε/2=0.7%. EBSD shows that the continuous small angle grain boundaries are produced during the fatigue. The small angle grain boundaries have a significant increase at 720°C, especially that case at Δε/2=0.7%.

Abstract: The aim of this study was to investigate the fatigue properties of Portland cement/multi-walled carbon nanotube (MWCNTs) composites. Multi-walled carbon nanotubes of varied functionality (unfunctionalised and carboxyl functionalised), synthesized by infusion chemical vapor deposition, and ordinary Portland cement (OPC) were used to produce pastes with a water to cement ratio of 0.45. The mixing amount of MWCNTs ranged from 0.1 wt.% to 0.6wt.%. The fatigue properties of the MWCNTs–OPC was characterised with the type and wt.% loading of MWCNTs used having a significant influence on the number of cycles to failure. The condition and degree of dispersion of the MWCNTs in the matrix at different length scales were studied using field emission scanning electron microscopy. Improvements of the fatigue properties were attributed to the MWCNTs arresting or retarding crack propagation through the cement by a bridging effect and hindering crack propagation. MWCNTs agglomerates were evident in the cement microstructure and the degree of agglomeration depended on the level of the mixing amount and the ability of the MWCNTs.

Abstract: In this study, a FE simulation model of the continuous extrusion process with double feedstocks is established. It is aimed to investigate the weld quality of AA6063 aluminium alloy profiles. The results show that with the height of preformed die increasing, the pressure-to-effective stress ratio (K) increases greatly and the welds can be improved. The maximum value of K reaches to 5.5. By observation the microstructure of the welding zone, the extrusion welding line does not extend to the product surface. No defects appeared on the surface of the extruded product. It is proved that the AA6063 product with good welding quality can be obtained by continuous extrusion with double feedstocks. These also provide the theoretical basis for expanding the application of the continuous extrusion process with double feedstocks.

Abstract: Flexural-torsional buckling of steel beams in high temperature is studied by adopting the method of theoretical analysis. The flexural-torsional buckling critical moment equations of steel beams under concentrated transverse loads are driven in high temperature ranging from 20°C to 300°C. In order to verify the validity of the theoretical analysis equations, a steel beam model under concentrated transverse load is designed. The flexural-torsional buckling critical moments and critical stresses are calculated under different temperature conditions. The influence of load point on flexural-torsional buckling critical moment and critical stress are obtained. The variation tendency of flexural-torsional buckling critical moment and critical stress against temperature are also presented.

Abstract: Due to the outstanding mechanical properties, carbon nanotubes (CNTs) are considered to offer the probability to enhance the properties of high-performance cementitious composites，and to reduce ecological cost of construction materials. Recent work in the area of concrete materials research has shown the potentiality of improving concrete properties by adjusting the mic-structure of cement hydrates, addition of nanotubes and controlling the delivery of admixtures. In this study, the multiwall carbon nanotubes (MWCNTs) were effectively dispersed in the water solution by applying ultrasonic energy. The results show that small amount of effectively dispersed MWCNTs can visible increase the strength of the cementitious matrix.

Abstract: Nickel-cobalt alloys have a wide range of industrial applications because of high strength, good corrosion resistance, heat-conductive, etc. As an example, they are used in the electroforming of moulds for die-casting and plastics and in electrotyping. In this paper, experiments on pulse electroforming of nickel-rich nickel-cobalt alloys were studied on SUS304 substrates from sulfamate electrolyte with different average current density, pulse frequency, duty cycle and different bath temperature. It is clearly observed in the nickel-rich deposits that effect of cobalt content gradually increases as the Co2+/Ni2+ concentration ratio and duty cycle increasing; The Co content seems to hardly change when pulse frequency changed from 500 Hz to 1000 Hz; The Co content decreases as current density increasing. High Co content and smooth surface topography can be obtained by reducing current density, increasing bath temperature and pulse duty cycle.

Abstract: To provide a theoretical basis for the optimization design of the composite foundation, we analyzed the long-pile length of rigid-long-pile & flexible-short-pile composite foundation using finite element software ANSYS as well as the effects on the whole performance of the composite foundation. The results show that under same vertical load, foundation settlement was significantly reduced with increase of long-pile length when long-pile length is less than 20m, but when the long-pile length is more than 30 m, reduction amplitude of settlement decreases significantly. When the long-pile length increases from 10m to 30m, stress distribution of the pile is similar in shape, with slowly increase of the values. It proves that long-pile length is an important parameter affecting reliability and economy of composite foundation, foundation settlement decreases with the increase of long-pile length, but if the long-pile length is longer than the effective pile length, the settlement of composite foundation will be little change.

Abstract: Based on the phase and mineral composition research of the magnetite, stage grinding stage selecting was adopted, through which, iron concentrate was got with productivity 16.60%, 66.15% grade and 61.26% recovery. This provides basis data for the use of this kind of magnetite.