Nanocrystallization of Al–Mm–Ni–(Fe, Co) alloys

Amorphous and nanocrystalline structures can be obtained in quaternary systems, containing Al, mischmetal (Mm) and two late transition metals (TM). Amorphous Al93−xMmxNi5(Fe,Co)2 (x=5, 8 at.%) alloys were produced by melt spinning method, and structures consisting of nanoparticles embedded in amorphous matrix were produced by isothermal annealing of initially fully amorphous ribbons. X-ray diffractometry (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) were used for characterization of the structures of the obtained alloys. The replacement of Al by Mm increases thermal stability of the amorphous phase, but decreases the difference between the crystallization temperatures, resulting in overlapping of the first two peaks on DSC curves. For all annealing temperatures, the volume fraction of nanoparticles was calculated. Thermal stability of all nanocrystalline aluminum alloys was also examined. Isothermal annealing was found to be an effective method for production of nanostructured Al-based alloys. Different volume fractions of fcc-Al phase and different sizes of nanoparticles can be obtained by varying annealing temperatures.