Applied Mechanics and Materials Vols. 121-126

Abstract: WC-NiCrBSi composite coatings on 0.45 % carbon steel were fabricated by laser cladding. The volume fraction (33, 43 and 60 vol. %) of WC particles with the powder size of 2 μm, 5 μm and 50 μm were added respectively into NiCrBSi powders to deposit composite coatings. The microstructure of the powders and the coatings were examined by scanning electron microscope (SEM) and X-ray diffraction (XRD). Results show that the compactness and uniformity of the coatings are good when WC particles size was 2 μm and 5 μm. However nonuniform distribution and deposit of WC particles on the bottom of the coating will occur when the powder size of WC particles was 50 μm and the volume fraction of WC was 33 %. When the volume of WC addition was higher than 60 %, the volume fraction of the retained WC particles in the coatings is obviously decreased. The dissolving and decomposing of WC increase with decreasing the powder size and increasing the volume of WC addition and the laser power.

Abstract: During the exposure process of a step-and-scan lithography, the transitional time between continuous scans does not produce production efficiency in which no scanning occurs. To minimize the transitional time and therefore to improve the productivity we introduce the motion-overlap scheme, which inserts a step-move between the overrun phase and the phase before exposure of next field along the scanning direction for wafer stage during the continuous exposure process. The simulation results show that the motion-overlap scheme enables the total time of two continuous scans of four different exposure field sizes reduce 8.28%, 7.11%, 5.87% and 4.53%, respectively, compared with the conventional motion planning method. This indicates that the theoretical derivation of motion-overlap planning method is effective.

Abstract: According to the microstructures in eutectic composite ceramic containing lamellae, the four phase model, which is composed of lamellae, eutectic interphase, matrix-atmosphere and effective medium, is put forward. Three phase cell that is composed of lamellae, eutectic interphase and matrix-atmosphere can be regarded as a composite inclusion. In view of Eshelby theory, the effective thermal expansion coefficients of eutectic composite ceramic containing the same orientation lamellae are determined. The eutectic composite ceramic is transverse isotropy and has two independent thermal expansion coefficients. The quantitative analysis shows that the effective thermal expansion coefficients have obvious size dependence.

Abstract: The influences of deformation temperature on microstructure dynamic recrystallization of 7A04-T6 ultra-high strength aluminium alloy by isothermal compression experiments in different deformation temperature on the 6300KN extrusion press. The experimental results show that both tensile strength and elongation increased with deformation temperature increasing. At 480°C, tensile strength reached 582Mpa and elongation increase to 9%. In the experiment, dynamic recrystallization of 7A04 aluminium alloy is mainly grain boundary nucleation and second phase particle nucleation. The grain size of 7A04-T6 aluminium alloy gradually refined with the deformation temperature increasing. Fracture morphology showed that rupture is belong to mixed rupture of intergranular and transgranular. With the deformation temperature increase to 480°C, grain size become small, the dimple in the fracture increase gradually, and existing the second phase particle in the dimple.

Abstract: In this paper, effects of nano-CaCO3 on compressive strength and Microstructure of high strength concrete in standard curing temperature(21±1°C) and low curing temperature(6.5±1°C) was studied. In order to improve the early strength of the concrete in low temperature, the early strength agent calcium nitrite was added into. Test results indicated that 0.5% dosage of nano-CaCO3 could inhibit the effect of calcium nitrite as early strength agent, but 1% and 2% dosage of nano-CaCO3 could improve the strength of the concrete by 13% and 18% in standard curing temperature and by 17% and 14% in low curing temperature at the age of 3days. According to the XRD spectrum, with the dosage up to 1% to 2%, nano-CaCO3 can change the orientation index significantly, leading to the improvement of strength of concrete both in standard curing temperature and low curing temperature.

Abstract: Two groups of porous metal bonded diamond composites (PMBDC), with and without rare earth (RE), were compacted and sintered under the same conditions. The effects of RE on the transverse rupture strength (TRS) and fractography of fracture surfaces (FFS) of PMBDC having different porosity were investigated. From the TRS and FFS’s perspective, the composites with RE are better than those without RE. Furthermore, the result suggests that there is a critical porosity where there are very apparent effects on the TRS and FFS. If the porosity of the composites is less than the critical value, the effects of RE increase with the porosity; if the porosity is larger than the critical value, the effects drop with the porosity instead.

Abstract: In this paper, studied was the low carbon and low silicon (0.003%C,0.3%Si) cold-rolling steel sheet whose reduction ratio was 81% annealed at 870 °C in the laboratory salt-bath furnace and heated for 180s.The evolution of micro-orientations of grain coarsening at 1050°C and 1150°C on cold-rolling samples that were annealed at temperature 870°C and heated for 180s was studied by EBSD technology.

Abstract: The surface temperature and equivalent heat conductivity of Flat Plate Heat Pipe (FPHP) under different heat flux, liquid filling and tilt angles are investigated experimentally. Electrical discharge machining (EDM) micro-channels wick are select as the wick inside FPHP. A set of experimental facility to measure the temperatures of FPHP is build up. The surface temperature along channels under different tilt angles, liquid filling and heat flux are measured by thermal couples. The results indicate that the temperatures are independent to the tilt angles and liquid filling. The equivalent thermal conductivity increases with the increasing of heat flux, and is 1.36 to 1.44 times to that of brass.

Abstract: Sapphire is an important wide bandgap semiconductor material for developing UV/blue optoelectronic devices, however because of its high hardness and chemical stability; it is mechanically and chemically difficult machine. In this paper, the scribing of sapphire by UV laser pulses is investigated under various conditions of pulse energies, scanning speed and repetition rate. The quality and morphology of the laser ablation of sapphire surface are evaluated by scanning electron microscopy. The mechanism of UV laser ablation of sapphire is discussed. The formation of grooves with high aspect ratio and good surface quality is achieved by selecting appropriate laser parameters. Scribing by pulsed UV laser therefore provide a new approach in the development of sapphire-based devices.

Abstract: Under the condition of grease lubrication, the skewed-roller slipping clutch was experimentally studied. The experimental bench was built up and the influences of geometrical parameters and operation conditions on torque ripple and temperature rising were clarified by the experiment, which laid the foundation for practical application of the skewed-roller slipping clutch in grease lubrication.