Primary crystallization process of amorphous Al88Ni6Sm6 alloy investigated by differential scanning calorimetry and by electrical resistivity

The primary crystallization process of α-Al nanoparticles from the amorphous Al88Ni6Sm6 ribbon was investigated by differential scanning calorimetry (DSC) under non-isothermal condition and by electrical resistivity (ER) measurements under both isothermal and non-isothermal conditions. The apparent activation energy, Ea, was measured to be 249.9 ± 12.5 kJ/mol by DSC and 245.7 ± 12.3 kJ/mol by ER. The local activation energy, Ec, was also evaluated and was observed to increase from 232.7 ± 4.7 to 268.5 ± 5.4 kJ/mol during the whole crystallization process. A general model (GM) based on the JMA theory was used to analyze the primary crystallization kinetic taking into account the impingement effect. The non-linear fitting of the isothermal ER results with this GM model gave an apparent Avrami exponent, nT, varying between 1.31 and 0.69 and an impingement factor λ close to 3. The local Avrami exponent, nα, measured by non-isothermal DSC at 10 K/min was found to decrease from about 3.0 to near 0.5 as the transformed fraction increased from 0 to 0.9. The results indicate that the primary crystallization process is typically controlled by the diffusion but a relatively important impingement effect is observed.