Jian Xin Xie

A Novel Forming Process of Copper Cladding Aluminum Composite Materials with Core-Filling Continuous Casting

To simplify forming process of cladding materials with high performance, such as copper cladding aluminum composite materials, and to improve the interface quality of cladding materials, a novel forming process called Core-Filling continuous Casting (CFC) for bimetal composite materials is proposed. A conceptual equipment is developed, and the forming of composite bars of copper cladding aluminum is investigated. The basic technique theory of CFC, the reaction and bonded state of interface and the interfacial bonding strength of the cladding materials, as well as the influences of technological parameters are analyzed. The composite bars of copper cladding aluminum with 24mm in diameter of core material and 8mm in thickness of cladding layer are successfully fabricated. The results show that: (i) the proposed CFC process is feasible in principle; (ii) the composite bars of copper cladding aluminum having metallurgical bonding interfaces can be fabricated by CFC process under the conditions of liquid copper temperature of 1250~1300°C, liquid aluminum temperature of about 700°C and drawing velocity of 12~24mm/min; (iii) the copper layer thickness distribution is uniform both in the directions of portrait and circumference and (iv) the interfacial bonding strength is higher than that of core aluminum.

Effects of Melt Cyclical Superheating Conditions on the Microstructure of FeSi2 Alloy

In order to avoid coarse primary-precipitated ε phase which prolong α+ε→β phase transition time in FeSi2 material prepared by conventional casting, a cyclical superheating process of melt for preparing FeSi2 with complete α+ε eutectic structure was proposed. The effects of melt superheating conditions on the microstructure of FeSi2 were investigated. The results showed that, with the increase of the superheating temperature, the superheating time, the recycling times and the cooling velocity, the size and quantity of the ε phase reduced. Meanwhile, the number of the fine eutectic structure increased. FeSi2 sample with uniform and complete α+ε eutectic structure was successfully prepared in the conditions of melt superheating temperature at 1550°C, superheating time for 10mins, recycling 3 times,melt cooling rate of 30°C/s.

Research on Dieless Drawing Process of Stainless Steel Tapered Tube

The traditional forming technologies of stainless steel tapered tube have some disadvantages, such as its complicated processes, few product specification, low production efficiency and high production cost. Dieless drawing is a new kind of near net-shaping process for fabricating tapered metallic tubes with large deformation per pass, high yield ratio of material and flexible production. Dieless drawing of stainless steel tapered tube was studied systematically in order to establish both temperature field model with respect to the changes of boundary condition and metal flow velocity during deformation, and a drawing speed controlling model with respect to the volume change of deformation zone. The models were verified by experiments in the present investigation. Finally, a continuous pickling process with variable-speed was proposed for tapered metallic tube, which was successfully applied to surface oxidation film removal of the stainless steel tapered tube.

The Surface Heat Transfer Coefficient Model of 7075 Al-Alloy Extrusion Product and its Temperature Prediction

Surface heat transfer coefficient is a key parameter for accurately predicting the extrusion product temperature near the die exit and then achieving isothermal extrusion by speed controlling. Based on the heat transfer characteristics of extrusion product during cooling process, a dynamic loading method of heat transfer boundary conditions was proposed. The surface heat transfer coefficient model of 7075 Al-alloy extrusion product was established using the dynamic loading method and inverse calculation comprehensively. The model indicated the relationship among surface heat transfer coefficient h, surface temperature T and initial temperature T0 as h=1.16T-0.97T0. Its accuracy is high enough for calculating the surface temperature of 7075 Al-alloy extrusion product. According to the model and the experimental data, the relationship between the product and the measured temperatures can be established. It provides an effective way to solve the problem that the extrusion product temperature near the die exit cannot be directly measured.

The Dynamic Recrystallization Model of 7050 Al-Alloy during Hot Deformation

In this paper, the compression stress-strain curves of 7050 Al-alloy under various deformation conditions were obtained, and the recrystallization structures were analyzed. The main parameters of dynamic recrystallization model were determined. The rationality of the model parameters were verified by hot compression and extrusion. The results show that the accuracy of the model is high enough for predicting the recrystallization of the 7050 Al-alloy during hot deformation. Comparison of the experiment and calculated results in hot compression shows that the maximum relative error of the recrystallization fraction is 11.4%. Comparison of the experiment and calculated results in hot extrusion shows that the maximum relative error of the recrystallization fraction is 13.0%, and that of the recrystallization grain size is 14.9%.

Preparation and Mechanism of Cu/Nano-TiO2/PBO Composite Fibers by Photocatalysis Electroless Plating

Cu/nanoTiO2/PBO composite fiber with low density, high strength, toughness and conductivity was prepared with a photocatalysis electroless plating method by reduction depositing Cu2+ on the surface of nanoTiO2/PBO composite fiber. The process parameters on the preparation of Cu/nanoTiO2/PBO composite fiber were optimized by the characterization of surface morphology, phase, composition, pull-out strength and resistivity of Cu/nanoTiO2/PBO composite fibers using SEM, XRD, EDS, electronic tester of tensile strength and multimeter, respectively. The mechanism of Cu coating nanoTiO2/PBO composite fiber was also discussed in this study. The results showed that Cu/nanoTiO2/PBO composite fibers were well prepared under the bath composition of CuSO45H2O 16gL-1, KNaC4H4O64H2O 15 gL-1, Na2EDTA2H2O 24 gL-1, HCHO 16 mlL-1, NaOH 14 gL-1, C10H8N2 24 mgL-1 and K4Fe (CN)6H2O 12 mgL-1 by the UV-light irradiated for 30 min. The diameter, pull-out strength and resistivity of Cu/nanoTiO2/PBO composite fiber were 20.2 μm, 2.25 GPa and 0.02864 Ωmm2m-1, respectively. Cu2+ ions on the surface of nanoTiO2/PBO composite fiber were reduced to Cu by photo-electrons which were generated of nanoTiO2 under the UV-light irradiated, and the primary Cu layer as a catalytic center promoted the reduction reactions of producing Cu/nanoTiO2/PBO composite fiber further.

Preparation and Mechanism of Nano-TiO2 Coatings on Poly(p-phenylene-benzobisoxazole) (PBO) Fiber

nanoTiO2/PBO composite fiber was prepared with a chemical method by depositing nanoTiO2 on the surface of PBO fiber which was treated by silane coupling agent. The process parameters on the preparation of nanoTiO2/PBO composite fiber were optimized according to the interfacial adhesion between the composite fiber and epoxy resin, and the coating mechanism of nanoTiO2/PBO composite fiber was also discussed. The results show that the uniform nanoTiO2/PBO composite fiber with high interfacial adhesion can be prepared on the PBO fiber which was pretreated by silane coupling agent with a concentration of 1.5 % for 35 min at room temperature, in which the nanoTiO2 aqueous solution with a concentration of 1.0wt% was ultrasonic dispersed for 1h in alkaline environment (pH 11), and then the PBO fiber was immersed in the dispersed solution at 60 °C for 6 h to prepare nanoTiO2/PBO composite fiber. The single fiber pull-out strength of the prepared composite fiber was increased by 85.28 % compared with that of the untreated PBO fiber. Silane coupling agent was a bridge of PBO and nanoTiO2, hydrogen bond association and like dissolves like were attributed to the improvement of interfacial adhesion between nanoTiO2 and PBO fiber.

Structure and Property of Nickel-Modified Ultrahigh Strength Al-Zn-Mg-Cu Alloy by Spray Forming

Six kinds of Al-Zn-Mg-Cu alloys, modified with nickel and zirconium, have been produced by rapid solidification using spray deposition(the Osprey process). The effect of nickel on the structures, mechanical properties of ultrahigh strength aluminium alloy is studied, and the probable maximum of mechanical properties is predicted. There are three nickel-rich phases, Al3Ni2, Al7Cu4Ni and MgNi2, forming in 1%Ni alloy, its ultimate tensile strength(UTS) increased with increasing extrusion ratios significantly while maintaining high levels of ductility, Futhermore, the extruded bars show enhancing more clearly than extruded plates in UTS and ductility. The content of Ni should decreased with increasing of Zn and Zr, and the highest properties(UTS=832MPa, Elongation=7.5%)are attained in 0.20Zr＋0.30Ni (wt%)alloy. In addition, the size, the shape and the homogeneous distribution of zirconium-rich phase produced in solidification is the key to effecting the mechanical properties of materials when Zr content is 0.2~0.5％.

Fabrication of W/Cu Functionally Gradient Materials by Multi-Billet Extrusion

W/Cu functionally gradient materials (FGMs) are fabricated by a novel process—multi-billet extrusion (MBE). Different W/Cu superfine powders made by mechanical alloying (MA) are used to improve the sinterability of W/Cu compacts. Good quality of three-layer W/Cu extrudes are obtained after confirming the extrusion parameters and the type and the content of binder during extrusion process. The green products are pressureless sintered at the temperature range of 1100-1300 oC for 1 h. W/Cu FGMs with relatively high density and high homogeneous microstructure are attained after sintering at 1200 oC for 1 h. The mechanisms for the enhance of sinterability and improvement of density of the mechanical alloyed (MAed) W-Cu powder products have been discussed. X-ray diffraction and scanning electron microscope are used to identify and observe phase constitution and microstructure, respectively.