STUDY ON THE PREPARATION OF NANO-TIB2 REINFORCED AL MATRIX COMPOSITES

TiB₂ particulate reinforced aluminum matrix composites (TiB₂/Al-MMCs) have received extensive attention due to a great potential in a wide variety of applications. Nano-TiB₂/Al-MMCs have also received attention from scholars with the development of nanotechnology in recent years. However, obstacles like agglomeration of nanoparticles in the matrix, and the difficulty of preparation of nanoparticulate reinforced metal matrix composites (PRMMNCs) still need to be resolved. This study summarizes the research progress of Al-matrix composites (Al-MMCs) in recent years and exemplifies the common preparation methods. Experiments were designed to study the common problems in the preparation of composite materials.

Two experiments were designed and completed in this study. First, TiB₂/Al-4.5Cu composites were synthesized through a mixed salt reaction method. The distribution of reinforcing particle in the aluminum matrix was observed. The predictive model of particle behavior in Al-4.5wt. %Cu matrix based on thermodynamic laws was re-examined. The experiment results are inconsistent with the prediction from a classic prediction model. Regardless of the rate of solidification and critical velocity (V_C), the most of the particles are rejected by advancing solid-liquid interface. Through review of classic particle pushing theory, this study attempts to derive a new boundary condition used to predict the behavior of reinforcing particles in a metal matrix during solidification based on the diffusion convection equations.

Second, nano-TiB₂/Al composites with a variety of volume fractions were synthesized by ultrasound assistance in a stirring method. The research has focused on optimization and improvement of preparation methods. High-energy ball milling (HEBM) and high-intensity ultrasound (HIU) were introduced into the fabrication process. Furthermore, a forging post-treatment process is used to process as-cast samples prepared by the experiment, so that the reinforcing particles in the composite material can be redistributed. The experiment results show that HEBM facilitates the mixing of nano-TiB₂ particles with salts. HIU helps distribute particles evenly throughout the matrix. The Vickers hardness and tensile strength of the composites were tested. The results indicated that the forging treatment has great influence on the mechanical properties of composite materials.