Papers by Author: Yu Hong Zhao

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Authors: Xiao Feng Niu, Wei Liang, Hua Hou, Yu Hong Zhao, Hong Xia Wang, Chun Xiang Xu, Jin Shan Zhang, Wei Li Cheng
Abstract: The Explicit Finite Difference (EFD) method is used for calculating the energy conservation equation during solidification. In order to improve the computational efficiency, the equivalent specific heat method is adopted to calculate the latent heat and the high order Alternating Direction Implicit (ADI) method is also applied, which is fourth order in space and second order in time. The degree of similarity between the simulation results and experimental results is analyzed quantitatively by the Hamming Distance (HD) for the first time, and results show that this high order mathematical model based on the equivalent specific heat method and the high order ADI method is faster and more accurate than the EFD method.
Authors: Hua Hou, Hong Hao Ge, Yu Hong Zhao, Wei Ming Yang
Abstract: In this paper, according to the characteristics of squeeze casting solidification process, the calculation model (FDM format) of the partial differential equations with high thermal conductivity is used to the numerical simulation of temperature field. Dynamic isolated multi-molten pool judgment method is used to determine the position of the pool and FEM is used to calculate the pressure of pool center. If the pressure of molten pool center has been down to 0, the liquid metal closed in the scale will be solidification under the condition of no pressure, and will shrinkage based on the way of gravity shrinkage. The equivalent liquid surface descending method of isolated molten pool is used to predict the formation of shrinkage defect; the simulation result is coinciding with experimental data.
Authors: Zhi Hong Guo, Hua Hou, Yu Hong Zhao, Shu Wei Qu
Abstract: A new high-strength magnesium alloy with better properties than that of AZ31 was developed. The effect of applied pressure during squeeze casting on microstructures and properties of the alloy was studied by means of techniques such as standard mechanical tester, Brinell Hardness Tester (BHT), and Metallographic Microscope (MM). The parameters studied include squeeze casting pressure, melt temperature and pressure holding time by using orthogonal experimental method. It was found that a squeeze casting pressure of 110 MPa and a melt and pressure holding time of 700 °C and 15s respectively gave a good combination of mechanical properties in AZ31 Mg alloy. This was primarily due to effective die filling, microstructural refinement and good heat transfer between the molten metal and the mould.
Authors: Yu Hong Zhao, Wei Jin Liu, Hua Hou, Yu Hui Zhao
Abstract: The Phase Field model of solidification processes was carried out coupled with temperature field model. The influence of interface atomic time on dendrite growth morphology in undercooled melt was simulated with pure nickel. The experimental results show that when the interface atomic motion time parameter is minor, the liquid-solid interfaces were unstable, disturbance can be amplified easily so the complicated side branches will grow, and the disturbance speed up the dendrite growth. With the increase of , the liquid-solid interfaces become more stable and finally the smooth dendrite morphology can be obtained.
Authors: Yu Hong Zhao, Yue Zhang, Da Hai Zhang
Abstract: Based on the Potts model, the grain growth of Si3N4 in liquid phase sintering process was simulated by Monte-Carlo method. A two-dimensional, square lattice is used to digitize the microstructure and the components and grain orientation are distributed randomly. The periodical boundary condition is applied. In the initial simulation, the grain growth and coarsening process driven by the reduction in interfacial free energy within a complex system involving a liquid phase were investigated with 32 orientations and different fraction of a liquid phase has been considered. Simulation was carried out with 200×200 lattice. The effects of the liquid amount on the grain growth mechanism and microstructures were discussed.
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