Formation of amorphous and nanocrystalline phases in Al90–xFexCr10 system by mechanical alloying

Pure elemental powders of Al, Fe and Cr corresponding to the compositions of Al90–xFexCr10 (x= 10, 25, 50) were mechanically alloyed by high-energy ball mill using a ball-to-powder weight ratio of 250:10. The structural evolution in these alloys was investigated by X-ray diffraction and transmission electron microscopy. Additionally, thermal stability of the mechanically-alloyed powders was tested by DSG. Amorphous phase was partially formed in Al65 Fe25Cr10 and Al4OFe50Cr10 mechanically-alloyed powders at the early stage of milling. Al5(Fe, Cr)2 and Al(Fe, Cr) compounds were formed in the middle stage of milling. In the last milling stage, a mixture of amorphous and nanocrystal was obtained in Al80Fe10Cr10 and Al65Fe25Cr10 mechanically-alloyed powders. Only nanocrystal was observed in Al40Fe50Cr10 mechanically-alloyed powder after long time milling. The crystallization temperature of these amorphous phases is about 150 K higher than that of the amorphous phase in Al–25 at%Fe binary system. It is proposed that the existence of Al–Cr atomic cluster in the amorphous matrix can improve the thermal stability of the amorphous matrix.