Interfacial segregation of Fe and Si on TiB2 surface and refinement of Fe-bearing intermetallic compounds and primary Si Part II Refinement of primary Fe-intermetallic compounds and primary Si through manipulating nucleation potency of TiB2 particles

Abstract

In Part I of this study, the interfacial segregation of Fe and Si at the Al/TiB₂ interface in an Al-3.7Ti-1.5B-1.0Fe-1.0Si master alloy was reported, with the structure and chemistry of the interfacial layers investigated using high-resolution transmission electron microscopy (HRTEM). In Part II, the TiB₂ particles, in which Fe and Si segregation had been established, were introduced into Al-Fe-Si and Al-Si alloys, respectively. The objective was to enhance heterogeneous nucleation of primary Fe-containing intermetallic compounds (Fe-IMCs) and primary Si particles in these alloys. Experimental results demonstrate that the primary β-Al_4.5FeSi IMCs and primary Si particles were significantly refined by the inoculation of TiB₂ particles exhibiting Fe and Si segregation on their surfaces. This refinement is attributed to the high nucleation potency of the segregated TiB₂, which provides both compositional and structural templating. Well-defined orientation relationships at the Fe-IMC/(Fe, Si)TiB₂ and Si/(Fe, Si)TiB₂ interfaces were observed, offering solid evidence that both primary phases nucleate heterogeneously on the surface of segregated TiB₂ particles. These findings further validate the proposed mechanism, that both structural and compositional templating are necessary to enhance the nucleation of primary phases.