Yu Tao Zhao

Microstructures of In Situ Synthesized ZrB2/AZ91 Magnesium Matrix Composite Synthesized by a New Method of Direct Melt Reaction

In-situ ZrB2/AZ91 magnesium matrix composite was successfully synthesized with Al/K2ZrF6+NH4BF4 by Direct Melt Reaction (DMR). The microstructures of the ZrB2/AZ91 magnesium matrix composite fabricated by direct melt mixing method were investigated. The results show that the size of ZrB2 particles is less than 1μm and even reaches to 100nm and the shape, amount and size of the β-Mg17Al12 phase in magnesium matrix composite have been greatly changed due to ZrB2 heterogeneous nuclei.

Microstructure of In Situ Synthesized Al3ti/6063 under Combination of Magnetic Fields

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.

Microstructure of In Situ Al3Ti0.4Zr0.6p/Al Fabricated with Electromagnetic Field

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 Al3Ti0.4Zr0.6 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.

Preparation and Microstructure of Nano ZrB2 Reinforced Aluminum Matrix Composites

The ZrB2 particulate reinforced aluminum matrix composites were fabricated via melt direct reaction method using Al-K2ZrF6-KBF4 components. 850°C and 30 min were the optimized synthesizing temperature and reaction time separately. The metallurgical thermodynamic and kinetic processes were then analyzed in detail. It reveals that the interphases include Al3Zr, AlB2, [Z and [ atoms. The ZrB2 particulates can be acquired through the molecular combination between Al3Zr and AlB2 or atomic combination between Zr and B atomics. The in situ reaction between reactive salts and molten aluminum takes place spontaneously, which exhibits the character of liquid-liquid reaction. Scanning electronic microscope observation results demonstrate that the sizes of ZrB2 particulates are almost 100-200 nm. The intervals between particles are almost 200-400 nm, demonstrating a unirom status of distribution.

Research on Activities of CaO-SiO2-B2O3 (Al2O3, Fe2O3) Slag System

A mathematical model on activities of CaO-based slag system has been established on the bases of ion-molecule coexistence theory of melted slag structure. The activities of CaO-SiO2-B2O3 (Al2O3, Fe2O3) systems are calculated. The effects of the content of B2O3, Al2O3 and Fe2O3 on activities are analyzed. The results indicate that the activities of CaO and 2CaO•SiO2 are decreased with the increases of B2O3, Al2O3 and Fe2O3. The effect of B2O3 is most remarkable. Moreover, the activity of CaO•SiO2 can be enhanced with increasing the contents of B2O3, Al2O3 and Fe2O3 respectively. These effects of Al2O3 and Fe2O3 are very similar, whereas the effect of B2O3 is most significant. As a conclusion, B2O3 is most effective to inhibit the formation of 2CaO•SiO2 as well as to promote the dissolution of lime.

Effect of Boron Mud on Melting Temperature of CaO-Based Steelmaking Slag

For the elimination of the fluorine pollution of steelmaking slag, boron mud is employed as fluxing agent for CaO-based fluorine-free slag. The effect of boron mud on the melting properties of slag is investigated. Hemisphere method is used to determine the melting temperature of samples. The results indicate that when the content of boron mud is lower than 7%, the melting temperature can be decreased by boron mud. With the content of boron mud increasing higher than 7%, the melting temperature is increased with increase of boron mud content. The basicity and the content of F2O3 have remarkable effect on the melting temperature of boron mud containing slag. When the basicity is in scope of 2.0-5.0, the melting temperature is in the range of 1350-1450°C correspondingly. The melting temperature of boron mud containing slag can be decreased significantly with increase of F2O3 content.

In Situ Fabrication and Microstucture of ZrB2 Particles Reinforced Aluminum Matrix Composites

Abstract：Aluminum matrx composites reinforced by in situ ZrB2 particles are fabricated from A356-AlB-K2ZrF6 system via in-situ melt reaction method, and the morphologies, sizes and distributions of the in situ particles as well as the microstructures, mechanical mechanisms of the composites are investigated by XRD,SEM,TEM and tensile tests. The results indicate that the morphologies of the in situ particles are mainly with ball-shape, the sizes are in nanometer scale and the distributions in the matrix are uniform. The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed.

Residual Stresses in Locally Long Fiber Reinforced Aluminum Parts

In locally long fiber reinforced aluminum parts two types residual stresses exist. They are the microscopic residual stress between fiber and matrix and the macroscopic residual stress between reinforced and unreinforced zones. The residual stresses between fiber and matrix in γ-Al2O3 long fiber reinforced aluminum alloy Al-6-1-1 were measured with X-ray Diffraction process as well as simulated with FEM method. The results indicated that the residual stresses in both fiber and matrix were distributed very unequally. The maximum tensile residual stress occurred at the boundary in the matrix and the maximum compressive residual stresses occurred near the boundary in the fiber. The macroscopic residual stresses between the reinforced and unreinforced zones were also measured with borehole method as well as simulated with FEM. It was found that the macroscopic residual stresses at most locations in both the reinforced and unreinforced zones were not harmfully high. However in both reinforced and unreinforced zones there were small sub-zones of very large tensile residual stresses.

In Situ Fabrication and Properties of Mg2Si/AZ91D Magnesium Matrix Composites

Mg2Si/AZ91D magnesium matrix composites are fabricated from AZ91D-Al2(SiO3)3 system by direct melt reaction method. The effects of the variation Al2(SiO3)3 addition contents to the microstructures and mechanical properties of the composites are investigated. The results show that the amounts of Mg2Si particles are increased and the structures of AZ91D magnesium alloy are refined with the Al2(SiO3)3 content increasing. When the additional content of Al2(SiO3)3 is 3wt.%, the tensile strength of the composite reaches 178.6MPa, which is increased by nearly 14.5% than that of AZ91D matrix alloy.

Characterization of (Al2O3)p/Al Composites In Situ Synthesized by Direct Melt Reaction Method

. (Al2O3)p/Al composites were in situ synthesized from Al-CeO2 system. The reinforcement phases, morphologies of particles and interfaces between particles and matrix were characterized by XRD, SEM, EDX, TEM and SAED. The in situ generated Al2O3 particles have various irregular shapes and disperse uniformly in matrix. The sizes of Al2O3 particles are normally less than 200nm. The interfaces between particles and matrix are clean. Moreover, there are large numbers of high density dislocations and the generated extensive micro-nano subgrains around Al2O3 particles. These novel characterizations contribute to the significant improvement of composites properties.