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Advanced high-temperature resistant metal-ceramic composites based on TiB2 for cutting tools
Halmazňa, Jiří ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
This diploma thesis deals with the preparation of new high-temperature resistant cermets based on TiB2. The hard ceramic phase is bonded by NiW metallic alloy, which was prepared by mechanical alloying using a planetary ball mill. The first part of the thesis is targeted to the optimization of mixing of both powders in the planetary ball mill. The procedure of preparation of powders mixture with homogenous particles distribution of the NiW alloy was designed and verified with simultaneous particle size refinement. The second part is focused on the microstructure characterisation and mechanical properties evaluation of sintered materials. In this case both powders, TiB2 and NiW, were mixed in a tubular mill and consequently compacted by a rapid hot pressing method at four different sintering temperatures. The influence of the sintering temperature on the microstructure development characterized by the density, porosity and grain size was monitored. The elastic modulus, fracture toughness, flexural strength and hardness were measured on prepared test specimens. The results of conducted experiments show a significant dependence of the microstructure and mechanical properties on applied sintering temperatures. The higher sintering temperatures are used the better mechanical properties are observed. However, the sintering temperature of 1375°C seems to be an optimal one. The sintering temperature of 1400°C leads to the significant losses of the metal phase due to sublimation of nickel resulting in increased porosity in the metal phase regions.
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Mechanical and structural characteristics of magnesium alloys reinforced with ceramic fibers
Halmazňa, Jiří ; Moravčík, Igor (referee) ; Zapletal, Josef (advisor)
This bachelor thesis deals the study of the mechanical properties of the alloy QE22 reinforced with SiC particles and Saffil fibers. This composite was produced by infiltration particles shape of the preform with molten matrix under high pressure. Test specimens prepared from the composite and the matrix were subjected to a tension strength test and compression test. The test results show pronounced asymmetry behavior in tension and compression of the matrix and composite. Adding the reinforcement into base material leads to significant increase of elastic modul, breaking strength and yield strength while reducing plastic properties. At the end of work was the behavior of the composite compared with the theoretical composite models.
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Advanced high-temperature resistant metal-ceramic composites based on TiB2 for cutting tools
Halmazňa, Jiří ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
This diploma thesis deals with the preparation of new high-temperature resistant cermets based on TiB2. The hard ceramic phase is bonded by NiW metallic alloy, which was prepared by mechanical alloying using a planetary ball mill. The first part of the thesis is targeted to the optimization of mixing of both powders in the planetary ball mill. The procedure of preparation of powders mixture with homogenous particles distribution of the NiW alloy was designed and verified with simultaneous particle size refinement. The second part is focused on the microstructure characterisation and mechanical properties evaluation of sintered materials. In this case both powders, TiB2 and NiW, were mixed in a tubular mill and consequently compacted by a rapid hot pressing method at four different sintering temperatures. The influence of the sintering temperature on the microstructure development characterized by the density, porosity and grain size was monitored. The elastic modulus, fracture toughness, flexural strength and hardness were measured on prepared test specimens. The results of conducted experiments show a significant dependence of the microstructure and mechanical properties on applied sintering temperatures. The higher sintering temperatures are used the better mechanical properties are observed. However, the sintering temperature of 1375°C seems to be an optimal one. The sintering temperature of 1400°C leads to the significant losses of the metal phase due to sublimation of nickel resulting in increased porosity in the metal phase regions.
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Mechanical and structural characteristics of magnesium alloys reinforced with ceramic fibers
Halmazňa, Jiří ; Moravčík, Igor (referee) ; Zapletal, Josef (advisor)
This bachelor thesis deals the study of the mechanical properties of the alloy QE22 reinforced with SiC particles and Saffil fibers. This composite was produced by infiltration particles shape of the preform with molten matrix under high pressure. Test specimens prepared from the composite and the matrix were subjected to a tension strength test and compression test. The test results show pronounced asymmetry behavior in tension and compression of the matrix and composite. Adding the reinforcement into base material leads to significant increase of elastic modul, breaking strength and yield strength while reducing plastic properties. At the end of work was the behavior of the composite compared with the theoretical composite models.
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