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-Al4.5FeSi 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.