In–situ synthesis of an Al–based composite reinforced with nanometric γ–Al2O3 and submicron AlB2 particles

Abstract

In this study, an Al–based composite reinforced with nanometric γ–Al2O3 and submicron AlB2 particles was fabricated via chemical reactions between Al and boron oxide, followed by hot extrusion. The volume fraction of in–situ formed γ–Al2O3 and AlB2 is 11.2 vol% and 6.3 vol%, respectively. The average size of γ–Al2O3 and AlB2 is around 50 nm and 500 nm, respectively, and the α–Al grain is 1.26 µm in the longitudinal section. The γ–Al2O3 particles either distribute inside of α–Al grains or exhibit particle chains or networks locating along grain boundaries, while AlB2 particles are uniformly distributed among the matrix grains. The Young’s modulus is averaged at 91 GPa, and the ultimate tensile strength and elongation of the composite at room temperature are averaged to be 426 MPa and 8.1 %, respectively. The yield strength at 350 °C is as high as 217 MPa. It is regarded that the relatively fine α–Al grains along with the γ–Al2O3 particles inside of α–Al grains and AlB2 particles are mainly responsible for room temperature strengthening, while the γ–Al2O3 particle chains or networks along grain boundaries play the key role in grain boundary strengthening at 350 °C. This work may provide new insights for designing and fabricating Al–based composite for elevated–temperature application.