Materials Science Forum Vols. 704-705

Abstract: Based on the plasma nitriding technique, the double glow plasma surface metallurgy (DG-PSM) technology was developed. This technology is also known as the Xu-Tec Process which utilizes solid metallic elements such as Ni, Cr, Mo, W, Ti, Al, Nb, Zr and their combinations to accomplish plasma surface alloying. Mo-Cr strengthened coating was prepared on the surface of low carbon steel Q235 by this technology. This coating is used to high wear resistant cold die LD steel. By experiment of the three different prescriptions in source cathode, the effect of source cathode composition on the coating has been studied. The technological parameters were as follows: The ratio of Mo and Cr were 2:1, 4:1 and 6:1. The work-piece material is Q235 low carbon steel. Holding time is 4h. Holding temperature 1050°C.Source cathode structure was threadiness. The consequences of composition analysis and microstructure observation results show that, most approaches the purpose of this research is the ratio of Mo and Cr is 6:1, and the alloyed layer has stronger adhesion with substrate.

Abstract: Ballistic impacting test has been conducted on laminated SiC/Al-Cu composite with three layers ceramic plates and metal multi-constrain, while the target sample was prepared through squeeze casting. The ballistic testing result showed that composite exhibited good structural integrity. Mass loss and length loss of projectile are 63.65% and 65.43% respectively, mainly resulted from abrasion of crushed ceramic particles and melting erosion itself. Multi-constrain of metal ensured to maximize the role of abrasion of crushed ceramic powder, in addition, the heat generated at instantaneous projectile-target contact led to partial corrosion on projectile. Subject to ballistic impacting, SiC ceramic was transgranularly fractured and crushed, metal lining was melt, deformed and destroyed, as well as the interface dissociation happened between ceramic and metal. These processes absorbed great kinetic energy of projectile, so as to stop the penetration of incident mass within the laminated structure. Layered composite failure was completed under synergistic effect of three fracture modes, including ceramic brittle fracture, interface debonding and metal fracture.

Abstract: As one kind of the advanced composite materials (ACM), FRP is now getting widely used in civil engineering for its advantages as light weight, electromagnetic isolation, high strength, fatigue resistance and corrosion resistance. This article wants to provide a quality control method for the FRP cables by eliminating its unwinding effect error. Firstly, two FRP-OFBG (Optical Fiber Bragg Grating) cables were fabricated in factory, and then the two specimens were tested by the MTS (material test system). Secondly, theoretical understandings with boundary conditioned formulas were provided for analysis on the unwinding process of the cable. After that the unwinding displacement of the FRP-OFBG cable was obtained by using the b-value method. Finally, a service ability assessment of the cable was given before the conclusions.

Abstract: Oxidation of U71Mn steels under three different reheating curves in air are experimentally analyzed in this study. Total heating time of the heating curves are numerical computed before experiment. The results showed that oxidation began from about 900K, become noticeable and accelerated at near 1100K and became fast from about 1250K. The total mass increase of oxidation under high, typical and low heating rate are 159, 131 and 104 mg/cm²，when the total heating time are 268, 286, and 316 minutes. Keywords: oxidation; steel; high temperature; reheating furnace

Abstract: The aluminium foam can be reinforced by compositing high hardness ZrO2 ceramic spheres. On the condition of preparing the precursor composed of the salt particals and ceramic spheres, the sample of composite aluminium foam is parpared by the press casting infiltration process.By the Hopkinson Bar hopkinson bar experiment, the result shows the composite sample holded the better impact performance than the aluminium foam .All of these should establish a basement to promote the deeper study and developmenter of composite foamed material.

Abstract: The Charpy impact test、hardness test、microstructure and morphology analysis of impact fracture by SEM were introduced to research the difference of impact toughness on 25Mn, which were in the station of hot-rolled、normalized and quenched & tempered. The resulted showed that the changes of load、deformation and energy exhaust in difference stage of deformation and fracture could be gained by Charpy impact test. 25Mn in quenched & tempered has more deformation resistance and deformation property than which in other stations. The total impact values was 6J higher than which in normalized in average, however, the crack propagation values was 16.78J higher in average. Ductile-brittle property of the material can be estimated by the analysis of crack formation values、crack propagation values and fracture morphology on samples.

Abstract: An advanced numerical model and its application in thermal processing of nonlinearly anisotropic scattering semitransparent materials are presented in this paper. The decomposition of the radiative transfer equation is deduced using spherical harmonics (P_N-approximation) method. Considering the transient problem, coupled radiative and conductive heat transfer model based on arbitrary-order P_N-approximation method is established. With the coupled model, the calculation accuracy of high-order P_N-approximation method is verified through comparison with theoretical solution and by the simulation results of other methods. Comparison shows that the arbitrary-order P_N-approximation method reproduces results with a high accuracy for linear and non-linear anisotropic scattering, while it can easily treat the nonlinear anisotropic scattering phase functions with desired order. Keywords: semitransparent material, coupled heat transfer, numerical simulation, spherical harmonics method

Abstract: TA15 airplane wall panels are used widely in aircraft manufacture, which consist of some reinforced ribs and a motherboard. Therefore, welding sequences of different reinforced ribs directly determine distortion and residual stress distributions of welding wall panels, and then affect the structure service performance. Therefore, it is important to get the optimistic sequence during manufacture processing of welding wall panels. This paper analyses and predicts regularities of distributions of residual distortion and stress under four kinds of different welding sequence namely, order welding sequence, head-tail welding, head-tail symmetry welding and center symmetry welding. Compared the distortion and residual stress of four kinds of sequences, it is obvious that the welding distortion is smaller and welding quality is better under head-tail symmetry welding sequence, and the order welding sequence is the worst. The simulated distortions are in good agreement with the experiments. So this study puts forward the best welding sequence when welding airplane wall panels, which adapt to any amounts of reinforced ribs welded with the motherboard.

Abstract: The present research study investigates the compressive and durable properties of concretes with steel slag, a by-product of the conversion process of iron to steel. For this purpose, a reference sample and twenty-four concretes containing steel slag were tested. The steel slag fraction used was “5–20 mm”, and the surface area of steel slag powder was 450m²/kg. Compressive strength at 7 and 28 days, and chloride penetration properties were measured. It is concluded that steel slag can be used in the production of concrete. In addition, the steel slag concretes present satisfactory physical properties. When proper amount of steel slag powder and steel slag fraction were used the concrete properties can be better than the blank one. Keywords: Steel slag, cement, coarse aggregate, concrete, durability

Abstract: Fractal analysis based on results of high temperature X-ray diffraction experiment was used to study the temporal-spatial properties of particles in In-40wt.%Sn melt. Partially-overlapping multirange fractal structure is observed in In-40wt.%Sn melt, and as temperature decreases from 800°C to 130°C, low fractal dimension was found to range between 2.000 and 2.669, high fractal dimension is still 3.000 without alteration. Moreover, low fractal dimension reveals a discontinuous change between 600°C and 700°C. Fractal characteristics of In-40wt.%Sn melt were correlated with the evolution of microstructure. The discussion was made in detail. Multirange fractal model was proposed to calculate transition region curves of multirange fractals. The results show that values of simulation show good agreement with experimental values, the maximum error is less than 1.3%. From the analysis, the range of the transition region between two fractal regions is speculated to be related with structure properties of metal melts. In addition, ultrafine particles’ aggregation mechanism was used to analyze the fractal morphologies. Keywords: multirange fractal; In-40wt.%Sn melt; microstructure change; X-ray diffraction.