Advanced Materials Research Vols. 295-297

Abstract: In elastic deformation range, this paper reports a finite element study of effect of length and diameter of the fiber on intrfacial stress of AZ91D metal matrix composites reinorced by short fiber. The nuit cell model is developde in ansys. It was found no infuence the fiber length has on the interfacial regions. There is considerable increase in intefacial von-Mises stress near the fiber end with increase in fiber diameter, and the region of stress transfer become wider. So, the risk of crack and debonding increase.

Abstract: At present, there are not any systematic researches on the fundamental performance of recycled concrete(RC). Thus it incites the inadequate confidence for the usage of RC. In this thesis, four different kinds of RC whose strength are C20、C25、C30、C35 respectively,are made using various mixing proportion. Then the influence rule of different recycled aggregate mixture quantities is drawn out, which consists the impacts on compressive strength, axial compressive strength, splitting strength, elastic modulus as well as the bending strength of RC. Meanwhile, the relation between the cubic compressive strength and the splitting strength, elastic modulus, axial compressive strength, bending strength is imitated, which provides study basis for the using of wasted concrete.

Abstract: Microstructure and properties of the high carbon equivalent gray cast iron modified by the rare earth metal are investigated by optical microscopy, scanning electronic microscopy, Brinell hardness and tensile testing. The results show that the primary austenite dendritic is refined, and the morphology of graphite is transformed from A-type to D-type undercooling graphite with increment of the rare earth metal (REM), even with the vermicular graphite present. The lamellae are becoming thinner with increment of rare earth metal. There are double peaks between the addition of the rare earth metal and the tensile strength/hardness. The iron would have the best comprehensive property when 0.30% REM is added.

Abstract: The effects of MgO and temperature on the properties and microstructure of mullite ceramics synthesized from high-aluminium coal fly ash and bauxite are investigated in this paper. The results show that when the batch containing 4 wt% MgO is heated from 1100 °C to 1500 °C, the bulk density and flexural strength increase obviously with the sintering temperature rising, mullite ceramics with flexural strength as high as 169 MPa can be obtained at 1500 °C with the addition of 2 wt% MgO. According to the XRD results, the corundum, cordierite and cristobalite phases disappear completely upon 1400 °C, it indicates that MgO addition may effectively promote sintering process. The results of SEM indicate that the prepared ceramics mainly exist in the shape of long parallelepipeds with the aspect ratio of about 7-10.

Abstract: In this paper, the commercial AZ91 Mg alloy with mixed rare earth (RE) Y、Gd and Nd has been investigated and effects of RE on die-casting microstructure and properties of die-casting Mg alloy has been also explored. The results indicate that RE can effectively refine the grain size of the alloy and improve inner microstructures transforming the reticular structure of Mg₁₇Al₁₂ phrase into granular or dotlike structure. At the same time, the amount of the compound at crystal boundary is less than that in the alloy without RE. In addition, the mechanical properties of AZ91 Mg alloy with mixed RE has been improved efficiently, and its tensile strength s_b can reach over 260MPa; its elongation δ can also reach over 4.5％. When the amount of mixed RE exceeds 5%, it will form coarse Al-RE compounds, which can low the mechanical properties of Mg alloy.

Abstract: The magnetostrictive Tb_0.22Dy_0.48Pr_0.3(Fe_0.9B_0.1)_1.93 alloy, and its 0-3 and pseudo 1-3 type epoxy-bonded composites were fabricated by curing without and with a magnetic field. The structural, magnetic and magnetoelastic properties were in investigated by means of x-ray diffraction, an alternating gradient magnetometer and a standard strain technique. The easy magnetization direction (EMD) is lying along <111> direction at room temperature. The 1-3 type composites has a larger magnetostriction than the 0-3 composite has, which can be attributed to the <111>-textured orientation and the chain structure.

Abstract: Mold quotation is one of the important issues concerns to enterprise. Due to the fact that there is lots of information properties such as uncertain, inconsistent and preference relationship exist in customer assessment. Through the analysis of the customer information investigated, a dominance variable precision rough sets approach is proposed to reduce the redundant information and discover internal relationship between the preference attributes and the basic bidding strategy. Finally an example was used to demonstrate the feasibility of the method.

Abstract: A copolymer based on 1,4-di(thiophen-3­yl)benzene and pyrene was electrochemically synthesized and characterized. The copolymer film showed a stable and well-defined redox process. Furthermore, five various colors under different potentials were presented on the copolymer film. Besides, the copolymer film showed fast switching time (1.5 s at 750 nm, 1.0 s at 1100 nm). Cyclic voltammetry study reveals that the copolymer film has reasonable stability.

Abstract: In order to study the effect of second phase precipitation on the refinement of microstructures during static recrystallization, the former researched non-quenched and tempered vanadium-nitrogen steel was chosen to conduct single and double-pass compression experiment by hot deformation simulator and the fraction of static recrystallization at different isothermal times was calculated. The precipitates were analyzed by TEM with accessories of EDS and energy filter. The results showed that precipitates in austenite during the pass isothermal times were mainly the (Ti, V) (C, N) with size varying from 55 to 140 nm, and during cooling and phase transformation were mainly vermicular VC with length in the range of 22-100nm and width 13-39nm. The key factor for refining the final structures: during short isothermal times is static recrystallization; during static recrystallization stagnation plateau is intragranular ferrites nucleated on precipitation phases; after stagnation plateau is intragranular ferrites promoted by the local solute-poor regions.

Abstract: Different temperature rises during finishing rolling of T8 cord steel were obtained through normal procedure (process 1) and controlled cooling procedure (process 2), and its effects on the microstructure and the mechanical properties were studied. The microstructure of T8 cord steel obtained by process 1 consisted of clusters of coarser and inhomogeneity sorbite colonies, and that obtained by process 2 consisted of equiaxed and finer sorbite colonies, with the similar interlamellar spaces of sorbite cementite in the two microstructures. The results of tensile tests showed that the tensile strength of T8 cord steel obtained by process 2 was higher than that obtained by process1 by 20MPa, with higher reduction of area and tensile elongation. In addition, the tensile fracture of T8 cord steel obtained by process 1 consisted of a lot of lotus cleavage plane, while that of T8 cord steel obtained by process 2 mainly consisted of finer dimples. That indicated that the smaller temperature rise of process 2 during finishing rolling can improve the mechanical properties of T8 cord steel.