Thermal Stability, Microstructure and Mechanical Properties of Nanostructured Al-Ni-Mm-X (X = Cu and Fe) Alloys Hot-Extruded from Gas-Atomized Powders

Abstract

The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of Al₈₅-Ni_8.5-Mm_6.5, Al₈₄-Ni_8.5-Mm_6.5Cu₁, Al₈₄-Ni_8.5-Mm_6.5Fe₁ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. All hot-extruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On ther other hand, the same substitution of 1 at% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as Al₃Ni, Al₁₁Ce₃ and Al₁₁La₃ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for Al₈₄-Ni_8.5-Mm_6.5Cu₁ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.