Transmission Electron Microscopic Observation of a Novel Al3Zr-η′ Core-shell Particle in Al-Zn-Mg-Cu Alloy

Abstract:

The Al₃Zr-η′ core-shell particles were observed in the Al-12Zn-2.4Mg-1.1Cu-0.5Ni-0.2Zr alloy using high-resolution transmission electron microscopy and electron diffraction. Two types of Al₃Zr particles appeared in the Al matrix: one a standalone Al₃Zr particle coherent with the matrix and the other an as-core Al₃Zr particle acting as nucleation for η′ precipitates resulting in a core-shell particle which is semi-coherent with the matrix. The shell is composed of η′ precipitates with four variants. The strain in as-core Al₃Zr is lower than the standalone, and a considerable amount of strain exists across the interfacial regions between the η′ precipitates and the matrix.

Key words:Aluminum alloys; Heterogeneous nucleation; HRTEM; Electron diffraction; Geometric phase analysis;