Investigation on nanocrystallization, thermal stability and hardness of amorphous Al86Cu6Y6Co2 alloy

In this study, nanocrystallization behavior, thermal stability, mechanical properties, and intermetallics formation of Al₈₆Cu₆Y₆Co₂ (at.%) as-spun amorphous ribbons were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FE-SEM) and microhardness. Kissinger, Ozawa, and Augis- Bennett methods were used to study the kinetics of crystallization. Activation energies for primary crystallization of the amorphous alloy in non-isothermal conditions using these methods (173–178 kJmol⁻¹) indicate a relatively high thermal stability. The mean amount of Avrami index (~ 2.1) revealed the first stage reaction is controlled by a 3-D diffusional growth with a reducing nucleation rate. The α-Al nanoparticles and intermetallic phases are embedded evenly into the glassy matrix during the first (623 K) and second reactions (723 K), respectively. The maximum microhardness of about 310 Hv is achieved in the Al₈₆Cu₆Y₆Co₂ alloy annealed at 623 K due to the enhancement of the solute content and the effect of α-Al nanocrystals.