Structure and selected properties of Al-Cr-Fe alloys with the presence of structurally complex alloy phases

The aim of the study was to supplement the data on the Al₆₅Cr₂₀Fe₁₅ alloy with binary phase structure and the Al₇₁Cr₂₄Fe₅ alloy with multiphase structure prepared with two different cooling rates from the liquid state. The presence of the structurally complex Al₆₅Cr₂₇Fe₈ phase was confirmed by neutron diffraction, scanning electron microscopy with the analysis of chemical composition and transmission electron microscopy. Additionally, the Al₈Cr₅ phase with γ-brass structure was identified for Al₇₁Cr₂₄Fe₅ alloy in both cooling rates from the liquid state. Due to the interesting features of structurally complex alloys, the wear resistance, magnetic properties, and corrosion products after performing electrochemical tests were examined. Based on pin-on-disc measurements, a lower friction coefficient was observed for the Al₆₅Cr₂₀Fe₁₅ alloy (µ ≈ 0.55) compared to the Al₇₁Cr₂₄Fe₅ multiphase alloy (µ ≈ 0.6). The average hardness of the binary phase Al₆₅Cr₂₀Fe₅ alloy (HV_0.1 = 917 ± 30) was higher compared to the multiphase Al₇₁Cr₂₄Fe₅ alloy (HV_0.1 = 728 ± 34) and the single phase Al-Cr-Fe alloys described in the literature. Moreover, the beneficial effect of rapid solidification on hardness was demonstrated. The alloys Al₆₅Cr₂₀Fe₁₅ and Al₇₁Cr₂₄Fe₅ showed paramagnetic behavior, however rapidly solidified Al₇₁Cr₂₄Fe₅ alloy indicated an increase of magnetic properties. The studied alloys were characterized by the presence of passive layers after electrochemical tests. A higher amount of oxides on the surface of the Al₇₁Cr₂₄Fe₅ alloy was recorded due to the positive effect of chromium on the stabilization of the passive layer.