Heterogeneous nucleation and orientation relationships of icosahedral phase with TiB2 inoculants

Abstract

This study confirms that crystalline TiB2 particles can act as a potent site for the heterogeneous nucleation of the metastable icosahedral quasicrystalline phase (IQC) formed in cast Al-Mn-Si-Cu-Mg alloys. The results show that a primary metastable IQC phase nucleates on facets of TiB2 particles. Electron backscatter diffraction patterns and selected-area electron diffraction patterns confirmed that at least five orientation relationships (ORs) exist between the stable TiB2 and the metastable IQC phase. The IQC adopts different ORs with the crystallineTiB2 particles to form low energy interfaces by matching close-packed planes at the interfaces. In the IQC phase, the close-packed planes are the 5-fold and 2-fold. Microstructural analyses show that inoculation has a noticeable influence on the size and distribution of the primary IQC phase, which in turn has a noticeable influence on the compressive properties of the investigated alloys. Due to their exceptional mechanical properties, these alloys could become a prime candidate for lightweight applications, especially in the automotive and aerospace industries.