Advanced Materials Research Vols. 154-155

Abstract: Billets of AFS with the thickness of 4.9 millimeters were manufactured by pack rolling process. SEM analysis for interfacial bonding and cell structures of AFS were carried out in detail. The results show that surface quality of the panel after pack rolling is obviously improved as compared to powder composite rolling using Al sheets. Macro-cracks of face sheets also completely disappear. The interfacial bonding in between Al tube and foamable precursor material have no micro-cracks and the existence of gap. Metallurgical bonding between Al face sheets and the core Al foams and uniform cell structures of AFS are achieved as the foaming temperature and foaming time are 700°C and 2 minutes, respectively.

Abstract: Self-lubricating h-BN/Ni coating was prepared on a medium carbon steel substrate by CO2 laser cladding using a powder mixture of NiCrBSi+5%h-BN(wt.%). Microstructures and phase structure of the coating were analyzed using SEM, EDS and XRD. Wear tests were carried out using a M100 pin-on-ring wear tester. The results show that h-BN/Ni coating has much superior war resistance and noticeably lower fiction coefficient under dry sliding wear test conditions.

Abstract: Due to the promising properties of high entropy alloy, TiVCrAlSi high entropy alloy coating was prepared on Ti-6Al-4V alloy surface by laser cladding. The microstructure and phase analysis of as-cast TiVCrAlSi alloy and laser clad coating were characterized by scanning electron microscope and X-ray diffraction. The results indicate that as-cast TiVCrAlSi alloy is mainly composed of (Ti,V)5Si3 and bcc phase. The laser clad coating is metallurgically bonded to the substrate with few pores and cracks. Laser clad TiVCrAlSi coating is also composed of (Ti,V)5Si3 and bcc phases.

Abstract: The present experimental study aimed to examine the selected machining parameters on Surface roughness in the machining of alumina nitride ceramic. The influence of cutting speed and feed rate were determined in end milling by using Cubic boron nitride grinding tool. The predictive surface roughness model has been developed by response surface methodology. The response surface contours with respect to input parameters are presented with the help of Design expert software. The adequacy of the model was tested by ANOVA.

Abstract: Biomodification of polyester film is a new field which can improve the surface property of material whithout environmental pollution and high energy consumption. Bacillus B-F which was isolated from waste water could biodegrade terephthalic acid. It was fermented and the broth was concentrated and used for surface process of polyester film. The modification lasted for 20 days. The surface property of the original and modified polyester film were tested. Contact angle examination showed that the hydrophilicity and surface free energy of the film was increased; XPS tests revealed the content of oxygen increased; FTIR showed that a small quantity of phenolic hydroxyl group appeared on the surface of the film; an oxygenase catalysed action might react at the surface of the film according to the degradation pathway of the simulacrum terephthalic acid.

Abstract: Semi-solid processing of metals is becoming popular as a new potential manufacturing technology for parts and components in automobile, electronic and machine industries.Up to now semisolid welding technology have not been used in industrial applications. A new process of semisolid metals welding is proposed; the process shows excellent formability and joining ability of semisolid metals, and differs from the process of melt welding or mechanical joining with screws or nails. In the process, semisolid 2A14 aluminum alloy was joint together and was rapidly solidified under pressure. The heat affected zone of the joint was decreased and the grain size of the joint was become small. The application range of the process is wide, i.e., from the electronic industry to arts. The advantages of this new semisolid welding process are (1) ease of joining, (2) good joining microstructure, and (3) ease of carrying out mass production.

Abstract: The present analysis combines the injection molding software Moldflow and the structural analysis software ABAQUS to study the thermal warping behavior induced by soldering process for FPC connecter. Due to the residual stress, the anisotropic material property and complexity of part geometry existed in the injected plastic housing of connector, thermal warping is induced by the circle thermal process as the FPC connector are soldered on mother board. In the present paper, the warping caused by injection molding process is modeled and simulated by Moldflow. Then, the residual stress, the anisotropic material property caused by different fiber orientation calculated by Moldflow are imported into ABAQUS as initial conditions through the Moldflow-ABAQUS interface module to evaluate the thermal warping caused by soldering process for FPC connecter. The crucial soldering process parameters have been identified and the Moldflow-ABAQUS simulation results are compared with the experimental results.

Abstract: Marine propeller blade is composite of the free form surface, its machining method has been a difficult thing. The blade is processed by 4-axis belt grinding machine in this experiment, this paper analyze that the wear of the abrasive belt and the processing precision and the material removal rate of the blade according to the grinding performance of the blade material, the structural features of the vane, and the theory of 4-aixs belt grinding machine. Draw formulas with time for the belt wear height and the actual grinding depth. The life expectancy of the ceramic abrasive belt is the longest, and its the material removal rate is maximum in Three kinds of belt，and when the belt line speed is 30m/s or so, the material removal rate is maximum.

Abstract: Ni/Al2O3 composite coatings were prepared by direct current (DC), single pulse current (PC) and pulse reversal current (PRC), respectively. The hardness and wear resistance of the coatings were investigated and the morphology and elements distribution in cross-section were analyzed by the application of SEM/EDS, XRF and XRD equipped with stress measuring device. The results show that the hardness of the three kinds of coatings increase with increasing Al2O3 content. The coating prepared by PRC plating exhibits higher hardness and better wear resistance, while that of DC plating has lower hardness and poorer wear resistance. The higher hardness and better wear resistance of coating of PRC plating can be ascribed to fine microstructure and weaker stress between substrate and coatings.

Abstract: Biomimetic surface structures have profound influences on the development of many emerging devices and systems. In this study, a sequential approach involving hot embossing and polymer casting for transferring biological surface structures to thermoplastic polymers were investigated and developed. The surface structure on shark skins (Carcharhinus brachyurous) was used as a case study. A PMMA pattern was fabricated by directly hot embossing the biological surface of the skin. The resulting PMMA structure was used as a casting master for rapid feature transfer onto PDMS surfaces. The replicated surface patterns on the polymer were found to be comparable with those on the shark skin. The water tunnel test of the flatplate sample pieces suggests that the drag reduction efficiency of the biomimetic shark-skin surface achieves 8.25% in maximum and 6.91% in average, which validates that this forming technology can be applied to the direct pattern transfer of the firm creatural scarfskins onto thermoplastic polymers.