Enhanced thermal stability of amorphous Al-Fe alloys by addition of Ce and Mn

Abstract The thermal stability of mechanically alloyed amorphous Al-Fe-based alloy powders, with nominal compositions Al₈₂Fe₁₆Ce₂ and Al₈₂Fe₁₄Mn₂Ce₂, was investigated using differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM) complemented by energy-dispersive x-ray spectroscopy (EDX). Analysis through DSC indicated that both Al₈₂Fe₁₆Ce₂ and Al₈₂Fe₁₄Mn₂Ce₂ alloys undergo a two-stage crystallization process. Notably, the initial crystallization temperatures for the Al₈₂Fe₁₆Ce₂ and Al₈₂Fe₁₄Mn₂Ce₂ alloys were determined to be approximately 525 °C and 550 °C, respectively. This high thermal stability is attributed to the delayed nucleation process induced by the presence of Ce and Mn within the Al-Fe matrix. During polymorphic crystallization, distinct phases such as β-AlFe, Al₁₃Fe₄ for Al₈₂Fe₁₆Ce₂, and β-Al(Fe, Mn), Al₁₃Fe₄, Al₁₀CeMn₂ for Al₈₂Fe₁₄Mn₂Ce₂ were identified. Furthermore, post-annealing of these amorphous alloy powders at elevated temperatures of 600, 700, and 800 °C led to distinct morphological characteristics based on the alloy composition. For Al₈₂Fe₁₆Ce₂, the particles preserved a nearly spherical morphology, with size distributions ranging from 1 to 5 μm. In contrast, for Al₈₂Fe₁₄Mn₂Ce₂, the particles exhibited an irregular shape with a broader size range of 1 to 15 μm.