Formation and structure of light-weight nanocrystalline alloys of the aluminium-nickel-RE system

X-ray diffraction, differential scanning calorimetry, and transmission elec tron microscopy were used to study the formation of nanocrystalline structu re upon controlled crystallization of Al-based amorphous alloys containing Ni and rare-earths (REs) Y,Yb, and Ce. For the alloys examined, the tempera ture and the activation energy of the amorphous-phase crystallization were determined. In all the alloys, a nanocrystalline structure was formed as a result of crystallization. The nanocrystal size ranges From 5 to 20 nm and depends on the chemical composition of the alloy and the regimes of its hea t treatment. The stability of the amorphous phase depends on the concentrat ion of a rare-earth element and its type. When crystallized, the alloys con tain aluminum nanocrystals randomly distributed in the amorphous matrix. Th e dependence of the average nanocrystal size on the chemical composition of the alloy and its variation upon isothermal holding are discussed.