Preparation of High-Strength Al–Mg–Si/Al₂O₃ Composites with Lamellar Structures Using Freeze Casting and Pressureless Infiltration Techniques

Abstract

Lamellar porous alumina scaffolds with the initial solid loadings of 20, 25, and 30 vol% were prepared by freeze casting using 5 μm alumina powders. With the addition of 3 wt% MgO–Al₂O₃–SiO₂ nanopowders in a eutectic composition as sintering aid, the maximum compressive strength of the sintered scaffolds reached (64 ± 2) MPa after sintering at 1,773 K for 2 h. The lamellar porous scaffolds were then filled with a molten Al–12Si–10 Mg alloy (in wt%) by pressureless infiltration at 1,223 K in a N₂ atmosphere, yielding the shell-like structure of the composites. The compressive strength of the upper part composite with the initial 30 vol% solid loading reached (1,190 ± 50) MPa, which was about 3.5 times as large as that of the matrix alloy.