Materials Science Forum Vols. 610-613

Abstract: Alumina (Al2O3) coatings in the thickness of 10μm and 15μm were prepared on the 4043 Al-Si alloy substrates by electroplating technology. Multiple mechanical properties of alumina coatings were evaluated by various techniques: the long distance microscope, Charge Coupled Device microphotographics, acoustic emission and strain foils. For the electroplating alumina coatings, the in-plane tensile strength is 68.1 MPa, the cohesive strength is 96.2 MPa and the adhesive strength is over 22.7 MPa. Three different directional microcracks, which are relative to the tensile directional and corresponding to two fail modes in the alumina (coatings)/4043 Al-alloy (substrate) system, were found.

Abstract: Mixing enthalpy of Al-Er binary alloys system has been calculated based on Miedema model, in which a new interaction parameters Li proposed by George Kaptay was considered: Li=h0i.exp(－T/τ0i ), which are used to indirectly calculate the activity of Er in Al-Er alloys and some other thermodynamic properties, such as excess Gibbs energy and excess entropy at 1073K. Firstly the interaction parameter between Al and Er is worked out, then formation ability of alloy solution is analyzed. The results showed that interaction parameter vs temperature can be taken as the form of LAl-Er=－240.29 exp(－T/2000) kJ/mol, which indicates that Al and Er atoms have a great tendency to form intermetallic compound of Al3Er during solidification. The Er concentration shows a negative deviation from Rault’s law, mixing enthalpy, excess Gibbs energy and excess entropy are all negative in the whole range of concentration, which reveals that Al and Er could dissolve each other up the liquidus line.

Abstract: The resistance spot welding process of galvanized steel sheet used in the body manufacturing of family car was studied, and the indexes of nugget geometry and tensile-shear strength of spot welds were tested. Four process parameters, namely welding current, electrode force, welding current duration and preheat current, and interactions among them were regarded as factors impacting indexes. Method using in mathematical models developing was nonlinear multiple orthogonal regression assembling design, which was optimized by the technology of variance analysis. The experimental results showed that more accurate prediction on nugget size and mechanical properties of spot welds can be obtained by the models optimized. With these prediction results, the optimization of welding process also was realized by the analysis to effect of the parameters and interactions on the welding quality.

Abstract: Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ carbothermic reduction and vacuum pressureless sintering. The effects of C content on the mechanical properties and microstructures of GT35 composites were investigated. As an excellent reducer, carbon provides an impetus for a series of reductive process. C content determines the melting point of the steel matrix, and directly affects the mechanism of dissolving and segregating of TiC particles, forming a netlike microstructure. Besides, the liquid steel whose viscosplasticity is determined by C content was coated on the surface of the composite and refrained the release of CO. The results showed that the good mechanical properties of steel-bonded cemented carbide GT35 composite were obtained with 0.9wt.% C at the same sintering conditions and the density reached 6.12g/cm3, the average bending strength was over 1229MPa after heat treatment, the mean hardness HRC was 69.4. It also showed that in-situ reduction of natural limonite was a feasible way to fabricate good performance GT35 composite with a relatively low cost.

Abstract: The strain rate sensitivity of helium plasma treated Nano Silicon Dioxide particles sol-gel coating Kevlar filaments (HPTNSDPKEVLAR) and concurrent micro-structural evolution. The results of SEM observation and contact angle analysis showed that the treated Kevlar filament had a rougher surface and lower contact angles than the untreated one. According to the FTIR results, the change of wettability was attributable to the amount of polar functional groups on the fiber surface introduced by the treatments. Moreover, the changes of physico-mechanical properties by HPTNSDPKEVLAR were analyzed by using tensile test at different strain rates range from ranging from 0.01 s-1 to 0.6 s-1. It was found that the materials were strain rate sensitive, and both the tensile strength and failure strain increased with increasing strain rate. The dependence of yield stress by HPTNSDPKEVLAR with strain rate followed Eyring’s equation, and may be characterized by implying the similarity in the onset of plastic deformation.

Abstract: The plasticity treatment of APPJ on microstructure and tensile deformation of Nano SiO2 coating Vectran in the dynamic states was investigated by specialized tensile testing at room temperature. With the addition of low-temperature Helium plasma treatment, Young's modulus and yield stress changed. It was found that micro structural parameter such as the activation volume was important to describe the Nano SiO2 coating Vectran and inter-phase strength between filaments and coating. The results of different APPJ treatments on the Nano SiO2 coating Vectran showed the change of the rate sensitivity of the filaments. The flow stress dependence of the strain rate sensitivity indicated that dynamical recover processes associated with the dislocation-dislocation interactions, which develop in the APPJ treatment Nano SiO2 coating Vectran and Vectran after small amount of deformation, leaded to strain localizations and early failure. Results revealed that APPJ treatment Nano SiO2 coating Vectran and the inter-phase would enhance the ductility of Vecetran at room temperature.

Abstract: The purpose of the present work was to investigate the effects of oxygen-plasma treatment on tensile deformation of nano-SiO2 sol-gel coating T-300 carbon fiber (HONS3C) were studied and a new concept for the nano-structural interphase between fiber surface and nano-coating provided in the paper. The tensile test results showed that besides the enhanced ductility of T-300 carbon fibers by nano-SiO2 sol-gel coating the T-300 carbon fibers treated by oxygen-plasma, the activation volumes of T-300 carbon fibers untreated and treated with oxygen-plasma ranging from 681.9628 to 32342(nm)3 by following Eyring’s equation were important descriptors for the properties of the nano-structural interphase between fiber surface and nano-coating, From the results of SEM and FTIR, it was observed that the uniform dispersion of the nano-SiO2 coating of the T-300 carbon fibers treated by oxygen-plasma not only formed a protective layer to cover the fibers, but also introduced the activated functional groups on the fiber surfaces.

Abstract: The effects of helium-plasma treatment on tensile deformation of nano-SiO2 sol-gel coating UHMWPE filaments (HONSUHMWPE) were studied and a new concept for the nano-structural interphase between fiber surface and nano-coating was provided. The tensile test results showed that in addition to the enhanced ductility of UHMWPE filaments by nano-SiO2 sol-gel coating UHMWPE filaments treated by helium-plasma, the activation volumes of UHMWPE filaments untreated and treated with helium-plasma ranging from 1101.875 to 16603.07(nm)3 by following Eyring’s equation were important descriptors for the properties of the nano-structural interphase between fiber surface and nano-coating, From the results of SEM and FTIR, it was observed that the remarkable uniform dispersion of the nano-SiO2 coating of the UHMWPE filaments modified with helium plasma not only introduced the activated functional groups, but also formed a protective layer on the fiber surfaces.

Abstract: The plasticity of APPJ treatment on microstructure and tensile deformation of carbon nanotube coating basalt fiber in the dynamic states was investigated by specialized tensile testing at room temperature. With the addition of low-temperature helium plasma treatment, Young's modulus and yield stress changed. It was found that micro-structural parameter such as the activation volume was important descriptors for carbon nanotube coating basalt fiber and inter-phase effect on strength. The different APPJ treatments on the carbon nanotube coating basalt fiber showed the change rate sensitivity. Results revealed that APPJ treatment carbon nanotube coating basalt fiber and the inter-phase would enhance the ductility of basalt at room temperature. From the SEM micrographs, an increase in surface roughness has been observed and the degree of fibrillation decreased after helium and oxygen plasma treatment. Contact angle analysis showed taht the treated Basalt filament had lower contact angles than the untreated one. Based on FTIR results, the change of wettability and surface energy depended the amount of polar functional groups on the fiber surface introduced by the treatments.

Abstract: Interfacial properties of four kinds of natural fibers (et. ramie, jute, sisal and kenaf) reinforced phenolic resin were studied by single fiber pull-out test and short beam shear test. Effect of fiber surface treatments on the interfacial properties was evaluated. It showed that interlaminar shear strength (IFSS) was considerably improved after fiber surface treatments, especially after the silane treatment. Concerns about the poor moisture resistance of natural fibers, effects of fiber surface treatments on the moisture absorption behavior of natural fibers were also investigated by gravimetric methods. The results showed that neither fiber surface treatments nor the environmental temperature has effect on the moisture absorption behavior of natural fibers.