Microstructure and Wear Resistance of TiB2/7075 Composites Produced via Rheocasting

Abstract

In this study, TiB2/7075 aluminum matrix composites were prepared via in situ synthesis. It was found that TiB2 particles are mainly quadrate. Large TiB2 particles (1–2 μm) agglomerate at grain boundaries, but most of the particles are on the submicron scale. Adding 4.5 wt.% TiB2 particles effectively optimizes α-Al grains in the 7075 aluminum alloy. By combining in situ reinforcing particles with the self-stirring effect of a serpentuator, rheocasting of the 7075 aluminum alloy was achieved in a simple and economical way. The average grain size of the specimen after rheocasting and heat treatment was smaller than 33 μm, and the shape factors were greater than 0.85. The wear resistance of the 4.5 wt.% TiB2/7075 aluminum matrix composite that was prepared via rheocasting and gravity casting was tested with loads of 30, 60, 90, and 120 N at a friction speed of 0.15 m/s for a duration of 30 min. Because of the optimized microstructure and increased hardness, the wear resistance of the 4.5 wt.% TiB2/7075 aluminum matrix composite was significantly better than that of the 7075 aluminum alloy, and the wear resistance of the rheocast TiB2/7075 aluminum matrix composite was better than that of the gravity cast one.