Papers by Author: Yu Tao Zhao

Abstract: With pulse magnetic field, it is use 2124-K2ZrF6-KBF4 as matrix metal to produce chemical reaction to gain (Al₃Zr+ZrB₂) p/2124 composite materials in this paper. In this paper, For the sake of researching the microstructure, the morphology, the size and the matrix distribution characteristics of the reinforced grain of prepared composite material , those test methods are used, such as optical microscopy, scanning electron microscope, X-ray diffraction analysis and so on. We will research the magnetic field strength how to influence size and distribution of Al3Zr +ZrB2 particle and the abrasion performance of (Al3Zr+ZrB2)P/2124 composite materials in the room temperature. Wear experiment is proceeding in the CETR UMT 3-V the testing machine and sliding friction is friction way with pin-disc but without lubricant, then analyzes the wear mechanism.

Abstract: During the process of in situ generated particles reinforced aluminum matrix composites, the introduction of the magnetic field can make the melt a forced movement, promoting changes in the conditions of melt dynamics, and thus plays the role in refining particles, changing the morphology and distribution. And particle size and distribution both are important factors affecting mechanical properties of the composite. Therefore, the introduction of the magnetic field can effectively improve the performance of composite materials. In this experiment, Al-K2TiF6 is used as reaction system to study the influence of combined rotating magnetic field on the microstructure of aluminum matrix composites, which can optimize the preparation process of aluminum matrix composites in the combined magnetic field.

Abstract: In-situ Al3Ti /A356 composites were synthesized by direct melt reaction method in Al-K2TiF6 system. The preparation techniques was discussed and the effects of Si, Mg, La (0.30%), Ce (0.30%) and multiple rare earth (0.15% La + 0.15%Ce) addition on microstructures of Al3Ti /A356 composites were investigated by X-ray diffraction and scanning electron microscope. The results show that the morphology and size of Al3Ti reinforcement are influenced significantly by Si, Mg and the optimal preparation process is composition with latter Si, Mg alloying. The Al3Ti precipitations during solidification process are restrained by 0.30% La addition or 0.30% Ce addition and lead in the uniform of Al3Ti size and morphology. The radial growth of Al3Ti is strongly restrained by rare earth composite addition, and the main morphology is slender-spherical like.

Abstract: In situ TiB₂/6061 composites have been successfully synthesized through chemical reaction between 6061 master alloy, Al-3B master alloy and Ti powder. The composites fabricated by direct melt mixing method was investigated by Scanning Electron Microscope (SEM), Energy Dispersive x-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), The results shown the existence of TiB₂ particles. The size of most TiB₂ particles were just in micron level, and even reached to sub-micron level. The increase in microhardness and tensile strength for the as-prepared composites with 5% particulate volume fraction (PVF) are up to 26.8% and 51.2% respectively.

Abstract: The K₂TiF₆ ,K₂ZrF₆ powder and aluminum were selected as the raw materials to in situ synthesize the particulates reinforced aluminum matrix composites. During the fabrication process the electromagnetic field was imposed. The atomic ratio of Al/Ti/Zr in the particulates is determined as 3/0.4/0.6. The Al₃Ti_0.4Zr_0.6 is a new kind of intermetallic compound, some properties of which fall in between those of Al₃Ti and Al₃Zr. Electromagnetic field plays an important part in fining particles and promoting their uniform distribution. When the electromagnetic induced intensity is 0.05T the particles have 0.5-2μm average size and uniform distribution in matrix. The crystal grains of matrix resemble equiaxed ones. The average size of grains are nearly 100μm, 50μm and 25μm when the electromagnetic induced intensities are 0, 0.025T and 0.05T seperately.

Abstract: In order to develop low carbon bainitic Cr-B steel, experimental procedures including melting, thermal simulation study and laboratory hot rolling were adopted. The dynamic CCT diagram was established, microstructure and properties of experimental steel were also analyzed. The transformation temperature of experimental steel lies between 650～400°C and final microstructure changes fromquasi-polygonal ferrite, granular bainite to lath bainite as cooling rate increases from 0.2 to 50°C.s-1. The microstructure of steel plates, air cooled or water cooled to 530°C then air cooled, is mainly composed of granular bainite and quasi-polygonal ferrite, and the large size islands in granular bainite are responsible for the low strength and poor toughness. However, steel plate with lath bainite, water cooled to roomtemperature, boasts high yield strength (672MPa) and superior impact toughness (127J at -20°C). Therefore, it is feasible to produce low carbon bainitic Cr-B steel with high strength and good toughness through controlling cooling parameters.