Composition templating for heterogeneous nucleation of intermetailic compounds

Abstract

Heterogeneous nucleation of intermetallic compounds (IMCs) is inherently more difficult than that of a pure metal or a solid solution. It requires not only the creation of a crystal structure but also the positioning of 2 or more types of elements in the lattice with specified compositions. This makes composition templating a very important approach to nucleation control in addition to structural templating. In this paper we demonstrate composition templating as an approach to enhancing heterogeneous nucleation of IMCs. We found that heterogeneous nucleation of Fe-bearing IMCs in Al-alloys requires a undercooling few tens of K, which is more than an order of magnitude higher than that for solid solutions. Segregation of Fe to the TiB2 surface (the Fe modified TiB2) can provide composition templating and hence enhance heterogeneous nucleation of -Al15(Fe, Mn)3Si2 resulting in a significant grain refinement.