Effect of new Al-P-Ti-TiC-Y modifier on primary silicon in hypereutectic Al-Si alloys

In this study, a new Al-P-Ti-TiC-Y modifier has been successfully designed to modify primary silicon in hypereutectic Al-20wt.%Si and Al-29wt.%Si alloys. The results show that the morphologies of primary silicon crystals are drastically changed from irregular morphologies, such as starlike (fivefold) and coarse platelet to regular morphologies. Statistical analysis shows that primary silicon sizes in modified Al-20wt.%Si and Al-29wt.%Si alloys (approximately 20 and 35 μm, respectively) are smaller than those in unmodified Al-20wt.%Si and Al-29wt.%Si alloys (approximately 100 and 250 μm, respectively). As compared with unmodified Al-20wt.%Si and Al-29wt.%Si alloys, the Brinell hardness values of modified Al-20wt.%Si and Al-29wt.%Si alloys are increased by 15.8% and 32%, respectively. The wear rates of the modified Al-20wt.%Si and Al-29wt.%Si alloys are lower than those of the unmodified Al-20wt.%Si and Al-29wt.%Si alloys (under loads ranging from 3 to 9 N), respectively.