Ding Yutian

Effect of Ball Milling on Microstructure and Mechanical Properties of Mg2B2O5w/6061Al Matrix Composites

Abstract Mg2B2O5 wisker/6061 (AlMg2B2O5w/6061Al) matrix composites were fabricated through the powder metallurgy (PM) technique. The relationship among the parameters of ball milling, powder characteristics, and mechanical properties of the hot extruded composites was investigated. The results show that the reinforcement whiskers accelerate the milling process by increasing the matrix deformation and enhancing the welding and the fracture of particles. Furthermore, the mixing process is modified by a higher milling speed and suitable milling time, which result in reduced crystalline size, improved homogeneity of the whisker distribution, as well as enhanced tensile strength of the hot extruded composites.

Effect of Rectangle Wave Pulse Current on Solidification Structure of ZA27 Alloy

The effect of rectangle wave pulse current on solidification structure of ZA27 alloy was studied. The results show that the wave pattern relies on the frequency range of harmonic wave and the energy of pulse current within the frequency range of pulse current. Imposed pulse current could induce the solidification system to oscillate. The frequency range and the relevant energy distribution of pulse current exert an influence on the amount of atoms involved for forming critical nucleus, the surface states of clusters in melt, the oscillating state of melt on the surface of clusters, the active energy of atom diffusion, the frequnce response of the resonance of bulk melt and the absorbability of the solidification system to the external work. Rectangle wave pulse current involves rich harmonic waves; the amplitudes of high order of harmonic waves are higher and reduce slowly, so it has a better effect on inoculation and modification.

Effect of high-energy ball milling on synthetic reaction in Al−TiO2−C system

High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al−TiO2−C system by changing the size, distribution state and wet ability of reactants. Reaction temperature characters (reaction ignition time, ignition temperature time, the maximum temperature and temperature rising rate) were changed by different milling time. The longer the milling time, the earlier the reaction, the quicker the temperature rise and the higher the maximum temperature. When the milling time exceeded10 hours, the reactivity of reactants was so high that the synthetic reaction could take place at 850°C directly without a long time pretreatment at 670°C. The microstructure of synthetic composites became uniform and the reinforced particles (TiC and α-Al2O3) became fine with milling time increasing.