Heterogeneous nucleation and orientation relationships of icosahedral phase with TiB2 inoculants.

This study confirms that crystalline TiB 2 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 TiB 2 particles. Electron backscatter diffraction patterns and selected-area electron diffraction patterns confirmed that at least five orientation relationships (ORs) exist between the stable TiB 2 and the metastable IQC phase. The IQC adopts different ORs with the crystallineTiB 2 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. [Display omitted] • This work confirms for the first time that crystalline TiB 2 inoculants can serve as an effective substrate for IQC phase nucleation. • EBSD and SAED patterns confirm that at least five orientation relationships exist between the close-packed planes of the phases. • The microstructural analyses show that inoculation has a noticeable effect on the size and distribution of the primary IQC phase. • The size and distribution of the primary IQC phase clearly affect the compressive properties. • As-cast, a compressive yield strength of 380 MPa, a compressive strength of 680 MPa, and a compressive fracture strain of 20 % were achieved. [ABSTRACT FROM AUTHOR]