Effect of Ce Addition on the As-Cast and As-Forged Microstructure of Fe-TiB2 Composites

Abstract

The effects of Ce addition on the as-cast and as-forged microstructure of Fe-TiB2 composites were explored. Fe-TiB2 composites with hypereutectic concentration were formed in situ from Fe-Ti-B melts at various cooling rates with the addition of the rare-earth element Ce. The size of both primary and eutectic TiB2 particles increased with a decrease in the cooling rate. Many clustered primary particles were found in the Ce-free specimens, while the addition of Ce significantly refined the TiB2 particles and scattered them into a dispersed distribution. Hot forging tends to further refine the size and enhance the number density of eutectic TiB2 particles. A decrease in interparticle spacing could be achieved by an increase of cooling rate, the addition of Ce, or hot forging. Tensile strength and hardness of the Fe-TiB2 composites both increased with decreasing interparticle spacing in accordance with the Hall–Petch relationship. Engineering strain was enhanced by Ce addition, then further improved by hot forging, and the proportion of dimpled region in the fracture surface was improved as well. Ce addition and hot forging enhanced both the tensile strength and the ductility of Fe-TiB2 composites.