Preparation of ultra-large intermetallic particles in Al alloys for accurate determination of their mechanical properties

Abstract

The mechanical properties of intermetallic phases are important parameters for designing aluminum alloys. However, accurate measurement of these properties was obstructed by the subsidence of small intermetallic particles in the soft matrix. In this work, the alloy compositions are designed through CALculation of PHAse Diagram (CALPHAD) so that each target phase is primarily formed in a wide temperature range during slow solidification, thus intermetallic particles as large as 0.6–3 mm were prepared by the solution growth method. The hardness and elastic moduli of 6 important intermetallic phases in aluminum alloys, including Al6(Mn, Fe), Al2Cu, α-Al8Fe2Si, β-Al9Fe2Si2, Al3FeSi2 and Mg2Si were obtained. The elastic moduli and hardness values of Al6(Mn, Fe) and Al3FeSi2 were measured for the first time by nanoindentation and Vickers hardness tests as EAl6(Mn, Fe) = 171 ± 10 GPa, HAl6(Mn, Fe) = 501 ± 5 HV and EAl3FeSi2 = 199 ± 10 GPa, HAl3FeSi2 = 811 ± 12 HV. The properties measured in this work are overall higher than other experimental data and closer to theoretically predicted values. For this sake, we believe these data are most accurate for these 6 phases. In addition, this work provides a simple method to prepare ultra-large single crystal particles in Al alloys.