Progresses in Fracture and Strength of Materials and Structures

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Authors: Guang Ze Tang, Xin Xin Ma, Ming Ren Sun
Abstract: Fluorinated amorphous carbon films (a-C:H:F) were deposited by plasma source ion implantation (PSII) with precursor gas of CH2FCF3 + C2H2 + H2 with various radio frequency (r.f.) power. Structures and properties evolution varied with r.f. power was discussed in detail. X-ray photoelectron spectroscopy (XPS), Raman spectrum, X-Ray reflection(XRR), atomic force microscopy (AFM) were used to analyze composition, chemical state, sp2 cluster structure, density and surface morphology of prepared films. Nano-indentation test was used to get hardness and modulus. The results show that with the increase of r.f. power, the size and amount of sp2 cluster increase, so does the surface roughness; however, the density and the hardness of films decrease.
1829
Authors: Xue Song Han
Abstract: Exit fracture, the main factor influencing the precision of workpiece, has already been extensively studied. In the case of nanometric cutting technology, the depth of cut is in the range of nanometer or sub-nanometer, there may be some different discipline dominating the exit fracture generation process. Molecular dynamics (MD) method, which is different from continuous mechanics, has already played an important role in describing microscopic world. The author carried out MD simulation of the micro-mechanism of exit fracture generation process, the results show that different types of burrs is generated depending upon materials ductility and the dimension of burrs may be increased with the increasing of depth of cut.
1833
Authors: Ping Ze Zhang, Zhong Xu, Gao Hui Zhang, Zhi Yong He, Hong Yan Wu, Zheng Jun Yao
Abstract: Conventional titanium alloy may be ignited and burnt under high temperature, high pressure and high gas flow velocity condition. In order to avoid this problem, a new kind of burn-resistant titanium alloy-double glow plasma surface alloying burn-resistant titanium alloy has been developed. Alloying element Mo is induced into the Ti-6Al-4V substrate according to double glow discharge phenomenon, Ti-Mo binary burn-resistant alloy layer is formed on the surface of Ti-6Al-4V alloy. The depth of the surface burn-resistant alloy layer can reach about 100 microns and alloying element concentration can reach 59%. High energy laser ignition experiments reveal that the ignition temperature of alloyed layer with Mo concentration about 10% is about 200°C higher than ignition temperature of Ti-6Al-4V.
1837
Authors: Kentaro Kozuki, Masaki Omiya, Kikuo Kishimoto, Hirotsugu Inoue
Abstract: The aim of this paper is to evaluate the cyclic interfacial strength between thin film and its substrate by cyclic nano-indentation tests. The specimen used in this study is PET substrate/ITO coatings layered specimen. From the indentation load and displacement curve, we proposed an evaluation method for the interfacial strength. The results are good agreement with the interfacial strength evaluated by peel test. After cyclic indentations, the surface profile was observed by atomic force microscope. The number of elongates increased with indentation cycles when the indentation load is low, whereas elongates number is almost constant under high load cases. These phenomena can be explained by simple models. In this study, two types of fracture modes are proposed. They are “subsidiary fracture mode” and “buckling mode”.
1842
Authors: Xiu Chun Wang, Mu Sen Li, Xi Qing Pan, Xiu Xin Wang, Xiao Jun Li
Abstract: This paper dealt with an environment protective phosphating with hydroxylamine sulphate as main accelerant. There were no nickel ion, nitrite, benzene and other harmful substances in the phosphated coatings. The structure, component and properties of the coatings were analyzed. The phosphating process and its influence on powder, electrophoresis and heavy anti-erosion coatings were also studied. The results showed that this processing had some virtues, all of the processing was carried out at room temperature; the phosphated coating was fine and the service life of the phosphating solution is longer. And also the phosphated coating had good properties.
1846
Authors: Shu Yan Xu, Xin Xin Ma, Ming Ren Sun
Abstract: BCN films were prepared with unbalanced magnetron sputtering boron carbide film followed by nitrogen plasma-based ion implantation at different voltages on Si substrate. The implantation voltages vary from 10 kV to 50 kV. The chemical states of B, C and N of the films were studied with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The nano-hardness and elastic modulus of films were measured by Nano-Indenter. The results showed that amorphous BCN films formed in the nitrogen implanted layer. The amorphous peak becomes obvious with increasing of the implanted voltage when the voltage is under of 40 kV. The Nano-Indenter measurement showed that the B-C bond content and the disorder degree affect the hardness and modulus.
1850
Authors: Xiao Ping Liu, Wen Huai Tian, Chao Li Guo, Dong Dong Chen, Zhi Yong He, Zhong Xu
Abstract: In this study, plasma niobium alloying of the TiAl based alloys has been carried out at 1050, 1100 and 1150°C. The effect of the alloying temperature on the characteristic of the alloyed layer was investigated by optical microscopy, scanning electronic microscopy (SEM), glow discharge spectrum (GDS) and energy dispersive spectrum (EDS). The results show that the surface roughness, chemical composition and thickness of the alloyed layer increased with the alloying temperature which is dependent on the sheath potential. A deposition layer formed on the TiAl surface at 1150 °C was resulted from the larger sheath potential or the stronger sputtering of source electrode.
1854
Authors: Li Sha Niu, Ting Ting Dai
Abstract: A 2-D Finite element simulation method was developed based on the kinetic law and the energy evolution during the whole process of deformation, which is used to investigate the creep size effects in polycrystalline thin metal film on substrates. Three diffusion paths (e.g. surface, grain boundary and lattice diffusion) are considered in the present model. The diffusion rate for these three processes was compared under different loading conditions with corresponding microstructure. It’s found that grain boundary diffusion is coupled with another diffusion channel. Creep size effects result from mass transferring in thin film. The model gave the quantitative results of the influences of the film thickness, grain size, and the constraints of the substrate on polycrystalline metal film diffusion. The simulated results present the evolution of the point defects in grain interior, the strain and stress field. The distribution of the crack-like stress in the grain boundary could explain the stress concentration mechanisms clearly and this also agrees with the literature results.
1858
Authors: Wu Tang, Long Jiang Deng, Ke Wei Xu, Jian Lu
Abstract: The crystal orientation, surface morphology, surface roughness and scratch properties of Au/NiCr/Ta multi-layered metallic films was examined by X-ray diffraction (XRD), atomic force microscopy (AFM) and a scratch test method, respectively. It was clarified that the surface morphology and surface roughness depend on the substrate temperature. The surface roughness decreases from 4.259nm to 2.935nm when substrate temperature changed from 100°C to 180°C, and then increases when substrate temperature above 180°C. The XRD revealed that there are only Au diffraction peaks with highly textured having a Au-(111) or a mixture of Au-(111) and Au-(200) orientation. The micro-scratch test reveals that both modes can be used for conventionally critical load determination, but the friction mode can additionally reflect the changes at different metallic film layers, the critical characteristic load was not sensitive to substrate temperature.
1863
Authors: Xiao Long Weng, Wu Tang, Yu Tao Wu, Long Jiang Deng
Abstract: Sn doped indium oxide (ITO) films were fabricated on polyethylene terephtalate (PET) substrate by magnetron sputtering at low deposition temperature using a 10 wt % SnO2-doped In2O3 target applied in the infrared regions as low emissivity materials. The microstructure and surface morphology of ITO films was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM); the resistivity was investigated by four-point probe technology. It was found that the film with amorphous microstructure has highest resistivity to 1.956×10-3 2.cm at low deposition temperature and the surface roughness and resistivity increase with the increasing Ar sputtering pressure from 0.5Pa to 1.4Pa. The most interesting is that the resistivity increases with the increasing surface roughness, it indicates that there are internal correlation between roughness and resistivity.
1867

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