Papers by Author: Qing Jie Zhang

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Authors: Zheng Yi Fu, D.H. He, Jing Ying Zhang, Wei Min Wang, Hang Wang, Qing Jie Zhang
Abstract: In this paper, we suggest PCH as a method of joining alloys. The temperature distribution in the samples during the joining process was analyzied. From the temperature distribution profiles in PCH joining, it is concluded that PCH for the joining has two advantages: (1) There is a temperature distribution peak along the sample. The contacting surfaces which need high temperature happen to obtain the highest temperature; (2) The parts to be joined at relatively lower temperatures can avoid the damage of heat attack. The optimal joining conditions were discussed. The PCH and HP techniques were compared for the joining of alloys. It was found that the high tensile strength joined structure of alloys can be fabricated by PCH method at lower joining temperature, shorter holding time, and lower pressure, compared with that by HP method. The PCH process was considered to be an eco-friendly process compared with the traditional heat diffusion joining methods.
Authors: Jin Yong Zhang, Zheng Yi Fu, Wei Min Wang, Qing Jie Zhang
Abstract: Recently research shows that heterogeneous model is needed to explain some complex combustion behaviors in SHS. However, more heterogeneous details be considered more difficulties will be faced. A micro-heterogeneous & macro-homogeneous model is proposed in this paper based on some previous works for this problem. Combustion compact is divided into lots of little units, which are composed of a large number of small particles. Considering a well-mixed situation, properties of every unit must be almost the same, so the compact can be treated as a macro-homogeneous system on the scale of these little units. During the combustion, every unit will have a heterogeneous properties and change; it can be gotten by a micro-heterogeneous model. Therefore, the micro-heterogeneous characters are connected with the Marco-combustion behaviors. Combustion dynamics of Ti-C-Fe system was studied to certify this model. Results show well consistency with experiments results.
Authors: Zhou Fang, Zheng Yi Fu, Hao Wang, Wei Min Wang, Qing Jie Zhang
Abstract: A novel approach was developed to prepare Ni-coated TiB2 cermet. Fine Ni particles with mean particle size of about 80 nm were impacted onto coarse TiB2 particles having a mean size of about 5 μm to form Ni-coated TiB2 powder by Hybridization. The conventional blended TiB2-Ni powder, as well as Ni-coated TiB2 powder, was sintered by hot pressing (HP) method and Spark Plasma Sintering (SPS) method. Compared with the conventional blended TiB2-Ni cermet, particle features and mechanical properties of the Ni-coated TiB2 cermet were investigated. The microstructure analysis reveals that the thickness of Ni film is around 4 nm. It is concluded that the mechanical properties of Ni-coated TiB2 cermet are superior to the blended TiB2-Ni cermet.
Authors: Qing Jie Zhang, Peng Cheng Zhai, Run Zhang Yuan
Authors: Kui Bao Zhang, Zheng Yi Fu, Jin Yong Zhang, Wei Min Wang, Hao Wang, Yu Cheng Wang, Qing Jie Zhang
Abstract: The equiatomic multicomponent CoCrFeNiCuAl high-entropy alloy powder was synthesized by mechanical alloying. The effects of milling time and heat treatment on the structure and morphology of the ball milled alloy were investigated. Single BCC solid solution structure appears when the alloy is ball milled more than 30h. The 60h ball milled alloy powder shows a mean particle size of 3 μm, which is actually hard agglomerations of nanosized crystals with crystalline size less than 10nm. The 60h ball milled alloy exhibits good chemical homogeneity. The single BCC solid solution structure transforms to a BCC and a FCC phases when annealled at 600°C for 1h, which can be attributed to the supersaturatable solid solution formation during the mechanical alloying process.
Authors: M. Zhang, Peng Cheng Zhai, Qing Jie Zhang
Abstract: This paper is aimed to numerically evaluate the effective thermal conductivity of randomly distributed spherical particle composite with imperfect interface between the constituents. A numerical homogenization technique based on the finite element method (FEM) with representative volume element (RVE) was used to evaluate the effective properties with periodic boundary conditions. Modified random sequential adsorption algorithm (RSA) is applied to generate the three dimensional RVE models of randomly distributed spheres of identical size with the volume fractions up to 50%. Several investigations have been conducted to estimate the influence of the imperfect interfaces on the effective conductivity of particulate composite. Numerical results reveal that for the given composite, due to the existence of an interfacial thermal barrier resistance, the effective thermal conductivity depends not only on the volume fractions of the particle but on the particle size.
Authors: Gang Chen, Peng Cheng Zhai, Qing Jie Zhang
Abstract: Creep behavior of SUS304 stainless steel is studied by small punch creep (SP-C) test. Series of SP-C testing for SUS304 stainless steel are carried out at 600°C. The time dependence of the central deflection is obtained by the SP-C testing at different load level and the creep deflection curves are quantitatively similar to those observed in conventional uniaxial creep testing. In this paper, an analytic approach based on Chakrebarty’s membrane-stretch model is used to interpret the SP-C test method. The relationship between specimen central deflection and equivalent strain is deduced, and the relationship between load and equivalent stress are established. The creep stress exponent of SUS304 stainless steel is determined by the theory formula and the data obtained in the SP-C testing. Comparison of the creep stress exponent of the Norton equations in SP-C testing and conventional creep testing is performed. The results show that the creep stress exponent is well consistent with conventional experimental results.
Authors: Peng Cheng Zhai, Gang Chen, Qing Jie Zhang
Abstract: The present paper investigates the creep phenomenon of the functionally graded materials under high temperature environment by the computational micromechanical method (CMM). Based on the real microstructure of the functionally graded interlayer with different component volume fractions, the emulation experiment is implemented for the creep test numerically and the creep parameters are obtained. A further series of simulation works are carried out to investigate the creep phenomenon of FGM interlayers in more detail. Numerical results show that the creep phenomenon is obvious not only for the metal-rich interlayers but also for the ceramic-rich interlayers. The creep property of ceramic/metal interlayer depends on the material’s properties of the ceramic obviously. It is remarkable that the creep strain rate of the ceramic/metal interlayer is larger than the corresponding one of pure metal under the same load when the modulus of the ceramic component is lower than the one of the metal component.
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