Papers by Keyword: Gradient Materials

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Authors: Agata Strojny-Nedza, Katarzyna Pietrzak, Marcin Chmielewski, Katarzyna Jach
Abstract: It has been known for many years that the incorporation of metallic particulates into a ceramic matrix can bring about the improvement of the mechanical properties of ceramics. Alumina/copper composites are well-known for their good frictional wear resistance, high resistance to thermal fatigue, high thermal conductivity as well as high absorption and dissipation of heat. The combination of the properties offered by alumina-copper composites makes them particularly interesting for wear applications in both automobile and aerospace industries. In the present paper we report on the design and production of a new class of alumina-copper functionally graded materials (FGM) which have technological potential for application in automotive brake disks. More specifically, this work deals with the development of the interpenetrating network structure of the FGM material. The manufacturing procedure was based on the gas-pressure infiltration of graded porous alumina preforms by liquid copper. The graded porous ceramic preforms with porosity ranging between 20 and 60% were made by casting foils made from slurries, the main components of which were alumina powder and rice starch powder (a pore forming agent), laminating these foils, subsequently burning-out the starch and last but not least performing a sintering process. A fundamental part of the presented investigations was to correlate the grain size of the alumina powders (Almatis, HVA FG and CT 1200 SG) and the pore size distribution, microstructure and selected mechanical and thermal properties of the porous ceramic preforms.
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Authors: Yu Mei Zhu, Zhi Hong Li, Xia Wan Wu
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Authors: Jana Andertová, Jiří Havrda, Radek Tláskal
Abstract: The work deals with preparation of functional gradient alumina ceramics with controlled porosity by slip casting method of aqueous alumina suspension containing pore-generating agent. The sol-gel transition of AlO(OH) was employed to stabilize pore-generating agent in the suspension. The composite bodies with layers of variable porosity were prepared. Based on dilatometer measurement the admission difference of irreversible dilatation changes #αirr between compounded layers was determined in order to prepare defect free bi-layer bodies. The dependence of physical and mechanical properties of as fired composite bodies on the porosity value was expressed.
223
Authors: Cheng Ping Zhou, Zheng Li, Fan Liu, Jing Tao Wang
Abstract: The recrystallization behavior of ultra-high purity aluminum (99.999%) during tube high-pressure shearing (t-HPS) was studied at the average strain rate of 0.2s-1 and 1.2s-1 respectively. The microstructure after t-HPS was characterized by electron backscatter diffraction (EBSD). Different recrystallization behavior at different strain rate of t-HPS was observed by the distinct microstructure evolution. The results showed that at higher strain rate, a finer grain size and higher recrystallization fraction were obtained. While the difference of recrystallization fraction between higher and lower strain rate decreased with increasing strain level. It has the potential for producing gradient materials as there is a grain size gradient along the direction of shear plane normal (SPN) which is more pronounce at strain level of ε=5.8.
516
Authors: Ni Zhong, Da Zhi Sun, Hui Du, Hong Yang, Xian Lin Dong
431
Authors: Ming Hao Fang, Yan Gai Liu, Zhao Hui Huang
Abstract: Ni/Al-Al2O3 gradient ceramic coating was prepared on Q235 steel by plasma spraying. Microstructure and corrosion behavior in boiling 5%HCl solution of the samples sprayed with this coating were investigated. The results showed that thickness of Al2O3 ceramic coating was increased greatly and almost no connected pores formed in the gradient coating due to the existent of Ni/Al-Al2O3 transition interlayer coatings. The corrosion resistance of Q235 steel with Ni/Al-Al2O3 gradient composite ceramic coating in boiling 5%HCl solution was greatly improved.
2647
Authors: S. Seifried, M. Winterer, Horst Hahn
277
Authors: Stefan Szczepanik, Marek Wojtaszek
Abstract: Aluminium RAl-1 and its alloy Al17Si5Fe3Cu1.1Mg0.6Zr composite materials were manufactured from powder mixtures by cold pressing, hot closed-die forging at 480oC and heat treatment. Powders ranging in composition in 20 wt.% steps of the alloy were mixed in a Turbula mixer for 1 h. The preforms with alloy concentrations of 80 and 100 % were hot consolidated at 480oC and closed-die forged at the same temperature. The effect of chemical composition on microstructure and mechanical properties in bending and compression was examined. Bend strength ranged from 400 to 540 MPa, compression strength from 415 to 744 MPa and hardness from 32 to 203 HB. Simulated distribution of component materials for a cross-section of the forging and shapes of the materials were analysed using LARSTRAN/Shape finite element program and are qualitatively comparable with the results obtained by forging.
1842
Authors: Aleksander S. Ivashutenko, Nikita V. Martyushev, E.M. Vodopyanov, Valeriy P. Bezborodov
Abstract: The article is devoted to the analysis of the possibilities to obtain gradient materials by the method of spark plasma sintering. Pure copper powders consisting of particles with the average particle size 100 microns and the nanodispersed powder of aluminum oxide were used in this study. Two powder compositions - pure copper powder and a mixture of copper powder and aluminum oxide powder were sintered:. As a result of the sintering process a sample with a double-area structure has been formed with a well-defined boundary between these areas. After sintering the copper powder porosity remained at the initial level. But having been mixed and sintered, the aluminum oxide powder particles agglomerated up to the average particle size of 80 – 100 microns.
76
Authors: Aleksander S. Ivashutenko, Nikita V. Martyushev, E.M. Vodopyanov, Eugene P. Naiden
Abstract: The article is devoted to the analysis of the possibilities to obtain gradient materials by the method of spark plasma sintering. Pure copper powders consisting of particles with the average particle size 100 microns and the nanodispersed powder of aluminum oxide were used in this study. Two powder compositions - pure copper powder and a mixture of copper powder and aluminum oxide powder were sintered:. As a result of the sintering process a sample with a double-area structure has been formed with a well-defined boundary between these areas. After sintering the copper powder porosity remained at the initial level. But having been mixed and sintered, the aluminum oxide powder particles agglomerated up to the average particle size of 80 – 100 microns.
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