Zian Yang, Zhilei Xiang, Jihao Li, Wenchao Sun, Yang Han, Jingcun Huang, Ziyong Chen
In this study, Nb was introduced into the Al-TiB 2 alloy synthesized by Melt Self-propagating High-temperature Synthesis (Melt-SHS), thereby producing the Al-3Nb-TiB 2 refiner that is compatible with Sr and resistant to Si poisoning. At a cooling rate of 2.2 K/s, the average grain size of the Al-12Si-4Cu-2Ni-Mg-0.02 Sr alloy refined with the Al-3Nb-TiB 2 refiner was reduced to 357.5μm. This represents an approximately 71.7% decrease compared to the 1325.5μm achieved with the commercial Al-5Ti-B refiner. Meanwhile, the effectiveness of Sr in modifying the Si phase was fully preserved. As a result, the mechanical properties of the alloy were significantly improved. Compared with the alloy refined using the commercial Al-5Ti-B refiner, the alloy refined with the Al-3Nb-TiB 2 refiner exhibited increases of 15.1% in yield strength (Rp0.2), 20.4% in ultimate tensile strength, and 35.4% in elongation. The Al-3Nb-TiB 2 refiner exhibited excellent compatibility with Sr owing to the absence of free B in the melt. The anti Si-poisoning mechanism involves the segregation of Nb atoms to the TiB 2 ( 0001 ) surface. This segregation promotes the formation of an NbAl 3 -like interfacial layer, which reduces the lattice misfit between TiB 2 and α-Al. First-principles calculations and atomic-scale structural characterization showed that Nb enrichment at the TiB 2 interface enhances its interaction with α-Al and suppresses its affinity for Si. The Al-3Nb-TiB 2 refiner integrated Sr-induced modification of the Si phase with grain refinement of α-Al in the Al-12Si-4Cu-2Ni-Mg-0.02 Sr alloy, leading to a significant improvement in the mechanical properties of the alloy.