Advanced Materials Research Vols. 418-420

Abstract: The influence of porosity on ultrasonic waves propagation in porous media, specifically in the bone tissue is examined in this work. The tissue is considered as a complex medium (anisotropic and heterogeneous) made of a rigid skeleton, filled by a medium which is supposed to be fluid. The theory of Biot is well suitable to describe the behavior of the ultrasonic waves in this tissue. The aim of this work is to determine how porosity affects propagation velocities of the various waves susceptible to propagate through the cortical or trabecular bone. By reference to this model and taking account of the viscous dissipation of the interstitial fluid, various propagation velocities were determined. A range of porosity extending from 0 to 1 and two types of fluid saturation (water and marrow) was considered. The results obtained show the influence of porosity on the propagation velocities of the longitudinal waves (the slow and the fast one) as well as of the transverse wave. Porosity and the nature of the interstitial fluid affect the dissipation phenomenon. According to the model suggested in this study and to the experimental results obtained, it can be affirmed that the determination of various propagation velocities in the bone leads to its characterization and can inform us about its pathological status.

Abstract: Electron beam surfi-sculpt is a new metal surface processing technology, which is potentially used in many areas. In this paper, forming mechaniam of electron beam surfi-sculpt has been investigated by experiments and numerical simulation. Electron beam surfi-sculpt of Ti-6Al-4V was realized by a new control system and a innovative hexagon scanning waveform. At the same time, microstructure of protrusions was analysed. All the results of experiments and simulation show that forming mechanism is the interaction of vapour pressure and surface tension, but surface tension plays a dominant role during electron beam surfi-sculpt process.

Abstract: Electroless palladium are introduced to ENEPIG surface coating technology, from reaction principle to prevent oxidation of nickel-plated, but the process conditions and parameters of practical application are whether or not mass-produce condition , need using a series of reliability experiments to validate it , to reduce risk coefficient of mass-produce , to satisfy customer requirement. Therefore, put forward a package of experimental programs, including experiment projects, experiment methods, instrument and equipment for test, evaluate requirement, test result and analysis etc , especially using TEM have in-depth analysis for interface alloy compound of ENEPIG coating player with SAC305 , systematically verified ENEPIG production technology are mature and reliable, it is considered to be versatile surface coating technology, and particularly suitable for application in gold bonding and surface mount hybrid assembly board which are high connecting reliability product, completely replace the current ENIG technology.

Abstract: Self-protection of flux-cored wire surfacing is a new way to improve mechanical parts surface properties, and can improve mechanical equipment in the harsh condition of wear-resisting, corrosion resistant, high temperature resistant and oxidation resistance abilities. This paper based on this technology, research on its reinforcement in the roof without bells chute board, first analyzes the board of chute working conditions, stress and aggrandizement requirements, and using ANSYS simulated the displacement field and the equivalent stress field during the impact process, to explain failure modes, Then from the view of experiment to research the effect of molybdenum and niobium self-protection of flux-core wire, the hard facing layer microstructure analysis show that hard facing layer can obviously increase the matrix micro hardness and impact toughness, The microstructure of Niobium surfacing layer is more delicate than molybdenum surfacing layer, impact toughness is higher and more suitable for strengthening chute lining board.

Abstract: An automatic high velocity arc spraying process was used to deposit a type of FeCrBSiMoNbW amorphous/nanocrystalline coating with substrate of AZ91 magnesium alloy. The microstructure of the coating was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDAX). The coating is about 250μm in thickness with low porosity and oxids. The results show that the microstructure of the coating can be classified into two regions, namely, a full amorphous phase region and homogeneous dispersion of α-Fe (Cr) nanocrystals with 30-80 nm in a residual amorphous region. Mechanical properties, such as nano-hardness, elastic modulus, were analyzed. The experimental results show that the coating has high nano-hardness and elastic modulus. The friction and wear experiments were operated on UMT-2 micro friction tester. The relative wear resistance of the FeCrBSiMoNbW coating is about 2 times higher than that of the conventional 3Cr13 coating under the same conditions. The main wear mechanism of the amorphous/nanocrystalline coating is the typical brittle spalling.

Abstract: The brazing process of magnesium alloy AZ31 was studied, and the mechanical properties of the weld were examined, and the main factors were analyzed through brazing furnace tests in this work. Only with the protection of self-made brazing flux, a lap joint with the average shear strength of 30MPa could be obtained in an ordinary resistance furnace without inert gas protection, which is much better than that without flux in which the shear strength is lower than 10MPa.

Abstract: Sm³⁺ doped transparent glass-ceramics of CaO-B₂O₃-SiO₂ (CBS) system were prepared and characterized.The precursor glass was prepared by melting method and annealed at 450°C for 2h and cooled to room temperature at a speed of 5°C/min.The appropriate heat treatment schedule to precursor glass was determined to be 2h at 600°C for nucleation and 3h at 810°C for crystallizition.The transmittion of glass-ceramics at the range of visable light is 68% in average. Five main emission bands of Sm³⁺ are centered around 564nm,605nm,646nm,679nm and 789nm,which correspond to the ⁴G _5/2→⁶H _5/2,⁴G _5/2→⁶H _7/2,⁴G _5/2→⁶H _9/2,⁴G _5/2→⁶H _11/2 and ⁴G _5/2→⁶H _13/2 transitions.Very strong luminescence at around 599nm is observed in glass-ceramics,This indicates glass-ceramics to be a better host for Sm3+ than precursor glass and a hopeful laser material.

Abstract: The top of COREX-3000 gasifier was numerical simulated and investigated the relationship between thermal conductivity and the thermal-stress field. It is concluded that when the thermal conductivity of the working lining and permanent lining is respectively 0.95W / (m•K) and 0.5 W / (m•K), the change rate of the top stress along radical direction is minimum.

Abstract: ZL114 aluminum alloy samples were treated by micro-arc oxidation using alkaline solution added different amount of nano-Al₂O₃ to improve the surface properties. Effects of the additives were investigated by thickness, hardness, morphologies and corrosion performance. The results indicated that proper amount of nano-Al₂O₃ had certain contribution with higher corrosion performance. And adding too much nano-Al₂O₃ decreased the property of ceramic coatings.

Abstract: Electroless nickel plating coatings on AZ91D alloy by phosphate pretreatment were prepared. The coating resembles a cauliflower and is compact. It consists of amorphous Ni-P. Potentiodynamic polarization curves of the Ni-P coatings in 3.5% NaCl show that the electroless Ni-P coating improves the corrosion resistance of AZ91D alloy and the highest corrosion potential reached to -0.513V vs. SCE. The results of the orthogonal experiment of process parameters indicates that temperature 80°C, time 120min and pH 7.5 can be considered as the optimum process parameters for electroless Ni–P plating on AZ91D alloy and pH value in the bath has more effect on corrosion potential than temperature and time.