Segregation of Mg at TiB<inf>2</inf>/Al interface mitigating the Zr-poisoning effect

Abstract

Interfacial segregation can modify a substrate's heterogeneous-nucleation potency. In Al alloys inoculated with TiB2, for instance, Zr segregation degrades TiB2’s nucleation potency and causes the loss of grain refinement, a phenomenon termed the Zr-poisoning effect. Here we use grain-refining tests to demonstrate that the addition of Mg can revive grain refinement from the Zr-poisoning effect. Using advanced transmission electron microscopy, we identify the segregation of Mg at the TiB2/Al interface, which causes the disappearance of the poisoning Ti2Zr two-dimensional compound (2DC). In its place, atomic layers of a nature close to the Al solid, which we term “Al-like layers”, develop, rendering the TiB2 potent again to catalyse the nucleation of α-Al. Thereby, Mg-segregation-modified TiB2 particles are reactivated for heterogeneous nucleation of Al grains. Apart from a mitigation of the Zr-poisoning effect, this work may shed further light on the manipulation of heterogeneous nucleation by atomic engineering of the nucleating substrate.