Advanced Materials Research Vols. 189-193

Abstract: Mechanical properties and microstructural evolution of an Al-Cu-Mg-Ag alloy during thermal exposure at elevated temperature were characterized by means of tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. The tensile test results suggested that tensile strength (σb) and yield strength (σs) reduced with both increasing exposure time and temperature. When exposed at 150°C, the Al-4.87Cu-1.2Mg-1.0Ag alloy exhibits good structural stability due to the excellent thermal stability of the Ω phase. SEM results showed that the specimen was fractured in a combined manner of intergranular and transgranular fracture. TEM results suggested the reduction of mechanical properties of samples was attributed to the coarsening of Ω phase and the precipitation of S' phase during thermal exposure.

Abstract: The precipitates of Al-5Zn-0.02In-1Mg-0.05Ti-0.5Ce (wt %) anode alloy were studied by scanning electron microscopy, X-ray microanalysis, high resolution transmission electron microscopy and selected area electron diffraction analyses in the present work. The results show that the alloy mainly contains hexagonal structure MgZn2 and tetragonal structure Al2CeZn2 precipitates. From high resolution transmission electron microscopy and selected area electron diffraction, aluminium, Al2CeZn2 and MgZn2 phases have [0 1 -1] _Al || [1 -10] _Al2CeZn2 || [-1 1 0 1] _MgZn2 orientation relation, and Al2CeZn2 and MgZn2 phases have the [0 2 -1] _Al2CeZn2 || [0 1 -10] _MgZn2 orientation relation.

Abstract: The nano-indentation and friction/wear properties of a magnetron sputtered SiC (silicon carbon) films on nanostructured titanium (produced by severe plastic deformation) substrate were investigated. The results show that the films exhibited low nano-hardness (10.6 GPa), low Young's modulus (83.3 GPa) and high hardness-to-modulus ratio (0.128). As sliding against Si₃N₄ (silicon nitride) balls (2 mm in radius) under Kokubo simulation body fluid (SBF) at room temperature, the films displayed superior friction/wear properties at the considerably high normal load of 1000g, with the friction coefficient of about 0.18, the special wear rate on the order of 10⁻⁶ mm³ N^-1m^-1 without film cracking and interface delaminating. The impressive film cracking and interface delaminating resistance is in accordance with the low hardness (high ductility) of the films and the small film-substrate modulus difference that was caused by the low modulus of the films.

Abstract: Firstly, the article gives a summarization of current study and research in the area of cemented carbide coating technology. Secondly, the article discusses the mechanism and method of coating technology, and compares the major leading approaches of coating technology. In conclusion, the article introduces the direction of future cemented carbide coating technology, based on current practical applications.

Abstract: A new chitosan ester derivative, chitosan p-hydroxybenzoate is synthesized, which is expected to have antimicrobial activity similar to parabens. The amino group of chitosan reacts well with acyl chloride to prepare a N-amic acid-chitosan. The amino group of chitosan must be protected before synthesizing a 6-O-chitosan ester. Phthalic anhydride is selected to react with chitosan to form N-phthalimide chitosan whose free amino group is protected. By six steps chitosan p-hydroxybenzoate is synthesized. FTIR, ¹H NMR and ¹³C NMR spectra show that the ester bond is formed between p-hydroxybenzonic acid and chitosan. Water solubility of the ester is slightly better than that of heptyl p-hydroxybenzoate, and its solubility in alcohol is greatly improved. Chitosan p-hydroxybenzoate showes broader spectrum antimicrobial activities. It has strong antimicrobial effects against Gram-negative, Gram-positive bacteria and yeasts. The MICs of chitosan p-hydroxybenzoate for Staphylococcus aureus and Escherchia coli are 0.01% and 0.025%, respectively.

Abstract: To meet the high requirements of fatigue strength and thermal stability for the large forging dies, the complex strengthening process tests of new high thermal stability die steel 5Cr2NiMoVSi were done. This complex strengthening process was nickel plating the RE boron penetration→ pre-cool quenching → high temperature tempering. The results show that the surface micro-hardness, high temperature oxidation resistance, thermal fatigue resistance and wear resistance of 5Cr2NiMoVSi steel can greatly be improved by these processes. It has achieved significant results for auto front axle large forging dies by using the materials and processing technology.

Abstract: The effects of different flow case, including resonant case, supercritical case and subcritical case, on the nonlinear surface waves of film with uneven bottom were analyzed. Derived from the potential flow theory, the fKdV equation on the nonlinear surface wave was obtained by the little parameter perturbation technique. The simulation was made by pseudo-spectral method, and the waterfall plot of the surface wave was illustrated with Matlab program. The flow, incompressible and inviscid, of which the surface tension and uneven boundary is considered. The results comprehensive surface waves located on the film is very different among the three flow cases.

Abstract: In this paper, we share our experience in information collection, management and online effective life calculation of tower crane. We propose a framework to complete collecting, classing, storing and processing of the working parameters of tower crane through wireless transmission and some commercial software, such as Visual Basic and SQL Server, based on the monitoring system of tower crane group. The load spectrum of tower crane can be gotten by numerical statement of above-mentioned information. Thus, the real-time effective life of tower crane is calculated and displayed directly through our algorithm. This life can be taken as a reliable reference in the safety detecting of tower crane. The effectiveness of the proposed method has been verified by a simple example of tower crane hoisting mechanism assessment. The results show that the system is accurate and reliable. The main advantage of the new method is its simplicity of implementation in lack of the load spectrum.

Abstract: In this paper, cobalt, tungsten and molybdenum were co-diffused into the surface of T8 steel by double glow discharge technique. A carbide layer with M6C＋MC was formed on T8 steel. Under the carbide layer was a diffusion layer of W,Mo,Co. Hardness of carbide layer is high over 1200~1400 HV_0.025 and can improve to 1400~1600 HV_0.025 after solution and ageing treatment. Hardness of the diffusion layer is only 400~550 HV_0.025, but it can improve to 800~1000 HV_0.025 after solution and ageing treatment. The carbide layer combides with the substrate in metallurgy and can not peel off from the substrate. The carbide layer on T8 steel possess same good tribological properties of M2 steel.

Abstract: Several different crystal types, different modified nano-TiO₂ and conventional TiO₂ were added into the coating to make some samples. A kind of nano-TiO₂ which can improve the reflectivity effectively was selected. The effect of the nano--TiO₂ content on the reflectivity and mechanical properties of the coatings.