Effect of Cu element on morphology of TiB2 particles in TiB2/Al-Cu composites
(1. Shanghai Aerospace Equipment Manufacturer Limited Company, Shanghai 200245, China;
2. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
2. State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: In order to explore the influence of Cu element on the morphology evolution of the in-situ TiB2 particles, the 10 wt.% TiB2 reinforced Al-5wt.%Cu based composite was prepared by mixed salt casting. The morphology characterization and transformation of TiB2 reinforcements caused by Cu element were investigated by multi-scale microstructure characterization and statistics techniques. In the case of controlled casting, 5 wt.% Cu addition was found to transform the TiB2 particle morphology from hexagonal plate with sharp edges and corners to hexagonal or tetragonal prism with chamfered edges and corners with the distinguishing growth steps both on the top surface and the side surface. The TiB2 growth in Al-Cu matrix followed the rules: nano-scaled spherical nuclei—polyhedron grains—chamfered hexagonal particles—hexagonal plates—chamfered particles with obvious growth steps. The adsorption energy of Cu on different crystal surfaces of TiB2 was caculated to reveal the influence mechanism and the results indicated that Cu was preferentially adsorbed on the (1011)TiB2 crystal planes, devoting to the small aspect ratio of TiB2.
Key words: shape control; preferential adsorption; TiB2 morphology; 2D-nucleation; growth step