Papers by Author: Bao Hong Tian

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Authors: Jing Guo Lei, Ping Liu, Bao Hong Tian, Xiao Zhi, Xiao Tian Jing
Abstract: The Cu-Ag-Cr alloy is a kind of aging hardening copper alloy and has excellent combination properties of high strength and good electrical and thermal conductivity. In the present investigation, the aging precipitation behavior of Cu-Ag-Cr alloy is studied, and the effects of aging processes on the microstructure and properties are discussed. Emphasis is on the correlation between the coherency and coarsening behavior of the Cr precipitates. When the alloy aging at low annealing temperatures, the homogeneous dispersed Cr precipitates are observed to be approximately spherical and keep coherent with Cu matrix in the Cu-Ag-Cr alloy, the coherency is lost between at 450°C~520°C, coherency on coarsening process of Cr precipitates at high annealing temperatures, the radium for coherent / semi-coherent transition of the Cr precipitates is determined from TEM micrographs as 15-45nm. Aging in the intermediate stage, coherent and semi-coherent particles can co-exist(15
Authors: Yan Li, Xiao Hong Chen, Ping Liu, Lin Hua Gao, Bao Hong Tian
Abstract: The behavior of plastic deformation of Cu-15Cr-0.1Zr in-situ composite under different degree of cold drawing deformation was analyzed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that both Cu and Cr phases are elongated along cold drawn direction and appear a fibrous morphology; However, Cu phase shows a thread-like fibrous morphology and Cr phase shows a band-like fibrous morphology. The two phases have a coherent relationship of (111)Cu //(011)Cr; When the degree of deformation(ε)is equal to 6.43, the relationship shows// [111]Cu // [110]Cr //cold drawn direction. Furthermore, forming two different morphologies of Cu and Cr phases during cold drawing is also analyzed.
Authors: Juan Hua Su, Shu Guo Jia, Feng Zhang Ren, Ping Liu, Bao Hong Tian
Abstract: The effects of different extent of cold rolling on the aging properties in Cu-Cr-Sn-Zn alloy are investigated by hardness and electrical conductivity analysis and microstructure TME (transmission electron microscopy) observation of the alloy. The results shows that dislocations provide nucleation site for precipitation during aging treatment, and result in the precipitation hardening effect from a finer size of precipitates. At 60% ratio of cold rolling and aged at 450°Cfor 1h, the hardness and electrical conductivity can reach 171.3HV and 71.5%IACS respectively.
Authors: Ping Liu, Shu Guo Jia, Feng Zhang Ren, Bao Hong Tian, Mao Sheng Zheng
Abstract: By means of a vacuum induction furnace, Cu-Ag-Cr alloy were produced. The wear property and mechanism of Cu-Ag-Cr alloy are studied, and its property was compared with a Cu-Ag alloy. The microstructure of the Cu-Ag-Cr alloy before wear tests was analyzed by transmission electron microscopy. Worn surfaces of the Cu-Ag-Cr alloy were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDS). Wear tests were conducted under laboratory with a special sliding wear apparatus that simulated the tribological conditions of sliding current collectors on contact wires, and alloy wire was slid against a copper-based powder metallurgy strip under unlubricated conditions. The results show that the wear rate of Cu-Ag-Cr alloy increase with the increase in the sliding speed and the sliding distance. Adhesive wear, abrasive wear and electrical erosion wear are the dominant mechanisms under the electrical current sliding processes. At lower sliding speed, adhesives wear and abrasive wear are the major wear damage, while electrical erosion wear and adhesive wear are the major at higher sliding speed. Under the same conditions, the wear resistance of the Cu-Ag-Cr alloy is 2~3 times of the Cu-Ag alloy.
Authors: Bao Hong Tian, Cheng Dong Xia, Shu Guo Jia
Abstract: Cu-Al2O3 composites were prepared by a new simplified internal oxidation process integrating with powder metallurgical process, and then the hot extrusion and the cold rolling processes were carried out. The microstructure, electrical conductivity, hardness, tensile strength and thermal stability of the composites were investigated. The results show that Cu-Al2O3 composites were fabricated successfully by the simplified process in which internal oxidation completed during the sintering. There are a mass of fine Al2O3 particles in size varying from 5 nm to 20nm dispersed in copper matrix after sintering 950 for 4h. After sintered at 950 for 4h and extruded at 950 followed with the cold deforming of 80%, the electrical conductivity, hardness, tensile strength and softening temperature of composite reach 81%IACS, 137HV, 561MPa and 850 respectively. It is considered that the dispersion strengthening and strain hardening have greatly contribution to the Cu-Al2O3 composites fabricated with the simplified process.
Authors: Bao Hong Tian, Ping Liu, Sheng Li Han, Ke Xing Song, Qi Ming Dong, Xianjie Cao, Liye Niu
Authors: Bao Hong Tian, Yong Liu
Abstract: A Fe-Al/WC composite coating was fabricated by using high velocity arc spraying (HVAS) and cored wire. The elevated temperature erosion behaviors of the coating were investigated with a grit blasting type erosion tester. The coating microstructure and eroded surface morphologies were analyzed by energy dispersion spectroscope (EDS), X-ray diffraction (XRD), scanning electron microscope (SEM) , transmission electron microscope (TEM) and image analyzer. The effects of incidence angle and test temperature on the erosion behavior were determined.
Authors: Yi Zhang, Ping Liu, Bao Hong Tian, D.M. Zhao, Shu Guo Jia, X.H. Cheng
Abstract: The effect of aging temperature and aging time on properties of Cu-3.2Ni-0.75Si-0.3Zn alloy were studied. The alloys were isochronally or isothermally aged after solution treatment. The cold rolling prior to the aging treatment was used to increase the precipitation rate .The microstructure of the alloy was studied by means of transmission electron microscope (TEM). The results show that the fine and dispersed precipitates are fully coherent with the Cu matrix and make the alloy possesses higher hardness and conductivity after the alloy was solution at 1173K and then aged at different time. The precipitates responsible for the age-hardening effect was Ni2Si.The transformation kinetics were studied by analyzing the electrical resistance variation of the solution Cu-3.2Ni-0.75Si-0.3Zn alloy in the process of aging.
Authors: Qi Ming Dong, Ping Liu, Juan Hua Su, He Jun Li, Bao Hong Tian
Abstract: By using the finite element method and large strain two-dimension plane strain model, the flaking damage of Cu-Fe-P lead frame sheet is investigated. The characterization of microstructure under surface flaking is the larger Fe particles embedded in the copper matrix. The numerical analysis reveals that at the interface of Cu and Fe there are greater strain mutation and intense stress concentration that is increased with particle diameter and the extent of deformation. This strain and stress concentration makes the interface initiate crack and develop crack easily. The micro-crack around the Fe particle is also attributed to surface flaking damage under the finish rolling deformation. The larger Fe particles should be avoided in the production of Cu-Fe-P alloy.
Authors: Ke Xing Song, Ping Liu, Bao Hong Tian, Qi Ming Dong, Jian Dong Xing
Abstract: Al2O3 dispersion strengthened copper composite (Al2O3p/Cu composite) was produced by internal oxidation. The hardness and electrical conductivity of the produced Al2O3p/Cu composite (0.60 wt.% Al2O3) subjected to high temperature annealing treatments after different cold work deformations have been investigated; the microstructures of the composite have also been analyzed by TEM. Results show that the microstructure of the composite is characterized by an uniform distribution of nano-Al2O3 particles in Cu-matrix; the composite can maintain more than 91% hardness retention after 1h, 1000°C annealing treatment; the recrystallization of the Cu-matrix can be largely retarded and only partially happened even annealing for 1h at 1050°C, following cold deformation of 84%.
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