Papers by Author: Xing Hong Zhang

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Authors: Chang Qing Hong, Xing Hong Zhang, Jie Cai Han, Qiang Xu, Xiao Dong He
Abstract: TiB2 -Cu cermet with the relative density of 92% was produced from titanium, boron and copper powders by combustion synthesis and subsequently pseudo hot isostatic pressing. To improve its mechanical and thermal physical properties, the two-time hot pressing sintering test was carried out at 1050°, 1090° and 1150°C respectively. The deformation behavior and variation of micro- structure and mechanical properties were investigated in detail. The results showed that the relative density and the flexural strength increase remarkably after two-time hot pressing. The relative density reaches 605.5MPa and the flexural strength reaches 96% when the two-time pressing temperature is at 1090°C, and the values increase 12% and 6% compared to that before two-time pressing.
Authors: Li Xu, Jie Cai Han, Xing Hong Zhang
Abstract: The TiB2-40Cu-8Ni composite prepared by combustion synthesis is investigated. Both 2D digital radiography (DR) and 3D computed tomography (CT) are used to test the specimens nondestructively. The result shows that ceramic phase aggregation is the main defect. Then the mechanical properties of samples are assessed by means of three-point-bend test. It appears that mechanical properties are related with the distribution of TiB2 phase and Cu phase. The scanning electron microscope (SEM) is also used to observe the crack growth of the bending test sample.
Authors: Qiang Xu, Xing Hong Zhang, Jie Cai Han, Wei Pan
Abstract: TiB2 based cermets with different copper content were produced from titanium powder, boron powder and copper powder by Self-propagating High-temperature Synthesis under conditions of Pseudo Hot Isostatic Pressing (SHS/PHIP). In order to obtain the optimal copper content, the effect of copper content on the microstructures and properties of TiB2 based cermets was investigated. The size of the TiB2 particles in the products decreased with increasing amounts of copper. The hardness (HRA) and bend strength increased firstly, then decreased with copper increasing. Their maximum values appeared at 20 wt.% and 40 wt.% copper, respectively. The porosity of TiB2 based cermets decreased with the copper content increasing due to good fluidity of copper. With the addition of copper, the fracture toughness of TiB2 based cermets increased gradually. Crack-tip plastic blunting by a ductile metallic phase and crack deflection are the principal mechanisms of toughness improvement of TiB2 based cermets. The range of optimal copper content in the TiB2 based cermets is between 40 wt.% and 50 wt.%.
Authors: Yue Feng Sun, Qiang Xu, Xing Hong Zhang, Jie Cai Han, Jin Huai Liu
Abstract: TiB2-Cu matrix composites from titanium, boron and copper powders were in-situ fabricated by exothermic reaction. The effect of the applied pressure on the mechanical properties of the composite was investigated. The results showed that when the applied pressure increasing, the relative density, bending strength, fracture toughness and hardness of the composites were on the increase due to the formation of fine microstructure and the improvement of densification with the pressure increasing. The high pressure is beneficial to the better mechanical properties.
Authors: Chang Qing Hong, Jie Cai Han, Xing Hong Zhang, He Xin Zhang
Abstract: Porous TiB2 ceramics with a three-dimensional interconnected skeleton were fabricated by high temperature pressureless sintering from fine TiB2 powders. The microstructure of the porous TiB2 ceramic was characterized by the enhanced neck growth between the initially touching particles. This neck growth was ascribed to the selective heating of TiB2 particles with different dimension. The porous structure prepared by the high-temperature sintering exhibited higher bending strength and fracture toughness in the present experiment. The improved mechanical properties of the sintered composites were attributable to the enhanced neck growth by surface diffusion.
Authors: Yong Zhang, Ping Hu, Xing Hong Zhang
Abstract: The influence of hot pressing temperature and SiC content on the microstructure and mechanical properties of ZrB2-SiC ceramics was investigated. ZrB2 containing 20 volume percent SiC were prepared by hot pressing at 1850, 1900 and 1950°C for 60 min. Fully dense ceramic was obtained after hot pressing at temperature of 1950°C. In addition, the materials with SiC content of 0, 10vol.%, 15 vol.%, 20 vol.% and 30 vol.% hot pressed at 1950°C were also investigated. Results showed that the grain size of the ZrB2 significantly reduced on adding 10vol.% SiC and then decreased slightly with further increasing SiC content, whereas the grain size of SiC exhibited a opposite trend. The flexural strength of ZrB2-SiC ceramics remarkedly increased on adding 10vol.% SiC due to the significant decrease of ZrB2 particle size and then slightly increased with increasing SiC content up to 20vol.%. However, further increasing SiC content led to a reduction of the flexural strength.
Authors: Yan Hui Wang, Jian Bing Zang, Xing Hong Zhang, Ming Zhi Wang
Authors: Xiao Dong He, Jie Cai Han, Xing Hong Zhang
Authors: Qiang Xu, Xing Hong Zhang, Jie Cai Han, Xiao Dong He
Abstract: Large-scale (Ti,Cr)B2-Cu composite from Ti, Cr, B and Cu powders was produced by combining combustion synthesis with Pseudo Hot Isostatic Pressing. The diameter of the synthesized product is 240 millimeter. The product was identified using X-ray diffraction and the result showed that only (Ti,Cr)B2 and Cu phases, without other phases, existed in the product. The analysis of the microstructure indicated that the skeletal structure had been formed in the (Ti,Cr)B2 solid solution phase. Fine (Ti,Cr)B2 reinforcement grew in near equivalent axis-like shape and some sintering neckings were found between the solid solution phases. The relative density of the synthesized product was 93.6% because the skeletal structure baffled the densification of the composite. The bending strength and fracture toughness of the product were 476 MPa and 6.8 MPa·m1/2 respectively.
Authors: Xing Hong Zhang, Ping Hu, Song He Meng, Jie Cai Han, Bao Lin Wang
Abstract: Two ZrB2-based composites were fabricated by hot-pressing with vacuum. ZrB2+20vol%SiC and ZrB2+20vol%SiC+8vol%TiB2 were selected as the starting compositions. The microstructures and phase constitutions of the composites were investigated and compared to these of monolithic ZrB2 material. For the ZrB2-based composites, with the addition of SiC particles, the excessive growth of ZrB2 materials is restricted and grain structure is refined. Meanwhile the fracture modes are changed, namely, from transgranular to mixed inter/transgranular. Strengthening mechanism is grain refining and the toughening mechanism is crack deflection, crack branching and grain refining. The role of TiB2 as an addition to the ZrB2 matrix was also examined and discussed.
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