Applied Mechanics and Materials Vols. 488-489

Abstract: With the common engineering-purpose ductile iron used as research subject, the research on rules of austempering parameters to influence the impact toughness and hardness of austempered ductile iron (ADI) was implemented in this paper by adopting the combination of theoretical, experimental and numerical simulation methods, and setting series of austempering parameters; After the impact tests and hardness tests simulated by the finite element software - ANSYS Workbench, the simulation data were analyzed by comparing with the experimental data. The experimental results showed that: austenitizing time was longer, ADI hardness was smaller while impact toughness remained unchanged; hardness was in linearly-decreasing trend with rise of austempering temperature, while impact toughness first increased and then decreased as the austempering temperature rose, with the maximum at the temperature 350°C; The effect of austempering time on the impact toughness was very few; extension of austempering time allows the hardness to increase slightly, but only a little.

Abstract: ZrAlYN films were prepared by magnetron sputtering at various N₂/Ar flow ratio. The structure, composition and thermal properties were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectrum. The results show that the deposited ZrAlN and ZrAlYN films possessed a single NaCl-type solid solution phase. The ZrAlN film was (200) strongly predominated. The (111) peak was prominently increased in ZrAlYN films and thus the preferred orientation changed to (111) and (200) co-predomination. The crystallinity of ZrAlYN films was gradually degraded with enhanced N₂/Ar flow ratio. Both ZrAlN and ZrAlYN films were exhibited a featureless fracture microstructure. The thickness of ZrAlYN films was consistently reduced due to more nitride produced on the surface of targets at higher N₂/Ar flow ratio. The ZrAlYN films deposited at 1:5 N₂/Ar flow ratio was proved to be the best oxidation resistance under annealing at 1000°C for 2h in air. As N₂/Ar flow ratio increased, the oxidation resistance of films was inversely deteriorated due to the decreased yttrium content in films.

Abstract: Based on heat resistant steel ZG40Cr24, test alloys were cast by intermediate frequency induction furnace with non-oxidation method by alloying of aluminium and silicon. The oxidation resistance at 1100°C for 500 hours of test alloys was carried out according to oxidation weight gain method. The thermal diffusion were tested by Laser Heat Conductivity. The thickness of oxide scale was detected by Coating Thickness Meter. Experimental results showed that the thermal diffusion of oxide scale affected its oxidation resistance exactly, the lower thermal diffusion coefficient matched the higher oxidation resistance. The oxide scale thermal diffusion coefficient of ZG40Cr24+2%wt.Si+4%wt.Al was only 0.00092cm².s^-1, endowing itself 0.0633g.m^-2.h^-1 oxidation weight gain rate, reaching the complete oxidation resistance. The mechanism of the effect of thermal diffusion on oxidation resistance lay in that the lower thermal diffusion represented the inert inner particles of materials, the few quantity of diffusion particles, and lower transporting and moving rate. So the oxidation rate slowed down, realizing higher oxidation resistant property for oxide scales.

Abstract: The use of melamine / urea modified phenol formaldehyde resin binder in the glass-fiber felt has led to products with lower free formaldehyde, higher water repellency and flexibility. This study gives a detailed description of the influence on the mechanical properties of the glass-fiber using the phenol formaldehyde resin with different levels of melamine and urea. Results show that, the free formaldehyde content reduced with the increase of the amount of urea and melamine, a small molecule of melamine and urea destroy the macromolecular chain of phenol formaldehyde resin leading to the decrease of breaking strength. At the same time, the decrease of the molecular chain is accompanied by the increase of flexibility.

Abstract: The channel effects of carbon nanotubes is studied by a fast proton in the framework of linearized hydrodynamic theory. General expressions of induced potential, the self-energy, and the stopping power are obtained for such a charged particle moving paraxially in a carbon nanotube. The influences of the damping factor and the carbon nanotube radius on the stopping power and self-energy are discussed. The results show that the velocity dependences of these quantities are strongly affected by the damping factor and the nanotube radius, the relevant results will be helpful for study of the transport of charged particles through nanotubes.

Abstract: The wake effect among dust grains in a flowing plasma is studied by the linear-response dielectric theory within the linear hydrodynamics model. The expression of potential is derived, and it can be divided into two parts: one is the screened Coulomb short-ranged repulsive potential, and the other is the long-ranged oscillatory wake potential. The numerical results show that both the amplitude and wavelength of the wake potential depend on the Mach number, in such a manner that the wavelength of the oscillating potential increases, while its amplitude decreases, with increasing Mach number.

Abstract: The interface between the reinforcement and the matrix is significant to metal matrix composites. The effect of aluminum (Al) content on interfacial microstructure and mechanical properties of TiO₂ coated carbon fiber reinforced magnesium matrix composites by squeeze casting technique have been studied (C/Mg). Mg-2wt%Al and AZ91D were used as alloy matrix. The obtained results indicate that the carbon fibers in both kinds of composites are well protected by TiO₂ coating, without any interfacial brittle carbide phase observed. The flexural strength of C_f-TiO₂/AZ91D (1009MPa) composites is 26.5% lower than that of C_f-TiO₂/Mg-2Al (1277MPa) composites. The lath-shaped precipitates of Mg₁₇Al₁₂ in AZ91D composites lead to the mechanical properties decrease.

Abstract: Ceramic fiber has great refractory and insulating ability. The coefficient of thermal conductivity is a significant characteristic of the fiber insulation materials, and shows the material thermal capacity. This paper not only research basic properties of ceramic fiberboard, but also focus on the influence factors of the effective thermal conductivity which include bulk density, temperature and moisture content.

Abstract: Thermal conducting silicone rubber composites filled with aligned nickel (Ni) nanoparticles induced by magnetic field were prepared by the solution mixing process. The structure, thermal, dielectric and magnetic properties of the silicone rubber composites were investigated by optical microscopy, laser flash thermal diffusivity analyzer, LCR digital meter and vibrating sample magnetometer. The results show that with the induction of magnetic field, Ni nanoparticles aligned form thermal conducting networks resulting in increase of the thermal diffusivity and relative dielectric constant of the silicone rubber composites.