Advanced Materials Research Vols. 418-420

Abstract: Nano surface engineering is a protection technology using nanometer material and nanometer technology, pointing at failure forms, characteristics and mechanism, comprehensively using a variety of traditional surface engineering technology. Nanocomposite coating technology which develops on the basis of the traditional composite coating technology was briefly introduced in the article. The research of application nanocomposite coating technology in plastic injection mould cavity surface treatment has just started. The nanocomposite coating technology was compared with the ordinary nickel electro-brush coating and the basic approach which realizes nanometer on the mould cavity was described. The advantages of nanocomposite coating were comprehensively and effectively explained. It can increase the coating thickness and hardness, improve the abrasive resistance, fatigue resistance and corrosion resistance of the plastic injection mould cavity, thereby enhancing the service life of mould.

Abstract: A new technique has been developed by infiltration during casting process to AZ91D magnesium alloy part. Through a melting process a alloyed surface layer was formed on the surface of the part in casting process, and the surface layer helps improve the corrosion resistance. The macro morphology, thickness, microstructure and properties of the layer were analyzed by digital, scanning electron microscopy, spectroscopy and corrosion measurement system. The results show that a uniform and dense infiltration layer on the surface of AZ91D part was obtained. This technique can fundamentally change the physical and chemical properties of magnesium alloy parts. More importantly, it is low-cost, green and environmental protection.

Abstract: The aim of present work is to investigate the mechanical and microstructural properties of dissimilar ADC12 and 6061 aluminium alloy joints produced by friction stir welding (FSW). The microstructure of joints has been observed by employing optical microscope. Furthermore, the welded joints have been tested under tension at room temperature in order to analyse their mechanical properties. At last, the scanning electron microscope (SEM) was employed to observe the specimens’ fracture morphology.

Abstract: Nano-titanium dioxide (N-TiO2) have already been studied and applied in the different fields due to its special surface, quantum size effect and high photocatalysis etc super properties. As a kind of biomaterials, biocompatibility and corrosion resistant of titanium are closely related to the surface oxide films. In this paper, nano-titanium dioxide with uniform granularity was synthesized using coprecipitation method. The effects of reactant mixture ratio and sintering temperature on synthesized N-TiO₂ were discussed. X-ray diffraction and Fourier transform infrared spectroscopy were employed to analyze structure of N-TiO₂. The results showed that prepared N- TiO₂ were all anatase and rutile coexistence and the larger ratio of carbamide to titanium oxysulfate (CO(NH₂)₂/TiOSO₄) is propitious to formation of metatitanic acid (TiO(OH)₂) precipitate. Meanwhile, with CO(NH2)2/TiOSO4 increasing, the start time and end time of precipitate decreased. The method used in this paper was a kind of simple process and easy to do.

Abstract: Aluminum bronze powders with free and 0.1wt%Ce were plasma spray welded on 45# carbon steel substrate, Effects of rare earth Ce on the microstructure and wear resistance of plasma spray welded novel aluminum bronze coatings were investigated. Tribological properties of coatings were tested on reciprocating sliding tester. Results showed that a small amount of Ce (0.1wt %) in novel aluminum bronze coating can refine the coating microstructure and the coating with 0.1wt%Ce process higher wear resistance compared to the Ce-free coating. Both of the coatings have different wear mechanisms.

Abstract: A kind of novel protective coating was prepared by using super-hydrophobic PbWO₄ nanocrystals as functional stuffing. The samples were characterized systematically by means of scanning electron microscope (SEM), contact angle analyzer, atomic force microscope (AFM) and Fourier transform infrared spectroscopy(FT-IR). The effects of various amount of nano-PbWO₄ particles on shielding ratio to 59.5 keV γ-ray were also discussed. The results revealed that the average diameter of PbWO₄ nanocrystals were about 32nm. The contact angle between the modified PbWO₄ and water was amounted to 153.08°, which showed that the modified PbWO4 owned super hydrophobic surfaces. The modified PbWO₄ had good dispersion and stability in organic solvents. Chemistry reaction happened between components of coatings and nano-PbWO₄ particles, thus it showed good compatibility with binders. The shielding ratio to γ-ray was up to 32%, and the hardness and levelling property was greatly improved.

Abstract: The efficiency of the high-speed milling process is often limited by the occurrence of chatter. In order to predict the occurrence of chatter, accurate models are necessary. With the speed increasing, gyroscopic effect plays an important pole on the system behavior, including dynamic characteristic and rotating behavior. Considering the influence of gyroscopic effect on rotating behavior, an updated model for the milling process is presented which features as model of the equivalent profile of tool. In combination with this model, a nonlinear instantaneous cutting force model is proposed. The use of this updated equivalent profile of tool results in significant differences in the static uncut thickness compared to the traditional model.

Abstract: An attempt was made to produce organic sealed micro arc oxidation coatings on ZM5 magnesium alloy using two different kinds of organic solution which are acrylics and PTFE. The thickness, potentiodynamic polarization test, corrosion weight lost and morphologies of the coatings were investigated. The results indicate that PTFE sealed micro arc oxidation coatings has relatively dense and uniform surface to show the best anti-corrosion performance.

Abstract: Numerical specimens with ramdom holes is established by particle flow code PFC2D and uniaxial compression tests are conducted. Studies have shown that the uniaxial compressive strength of the specimen accelerated decline while the porosity increasing uniformly. With the increasing of the porosity，the plastic of the specimen increases.

Abstract: Now the protection method for PCB welding board, widely used coating technology is ENIG , but in use course found that the coating will appear “black mat” that is fatal flaw in the welding process, in order to solve this problem, the engineers and technicians have taken various methods of strict control parameter, despite the improvement, but has not eradicated “black mat” this hidden trouble .Electroless palladium layer is introduced in ENEPIG surface coating new technology, from the reaction mechanism stopped nickel-plate oxidation, in the process of immersion gold blocked off nickel-plate contacted with Immersion gold solution, and effectively prevent pervasion and migration of nickel , thus effectively inhibit oxidation of nickel surface, prevent the “black mat” flaw . Not only have given the technology production process and parameter control, but also have microcosmic appearance and diffusibility analysis for the products by using SEM and EDS , the results showed that palladium layer is non-crystalline film with good uniformity of coating thickness, and did not find pervasion of nickel on gold surface, successfully achieve ENEPIG PCB mass production, replace ENIG technology .