Crystallization behavior of a gas atomized Al85Ni10La5 amorphous alloy

Al85Ni10La5 (at.%) alloy powders were fabricated using gas atomization. X-ray diffraction analysis revealed that powders in the size range of <500 mesh (<25 μm) are amorphous. The crystallization behavior and kinetics of the amorphous Al85Ni10La5 powders (<25 μm) were investigated during continuous heating and isothermal annealing. The amorphous Al85Ni10La5 alloy undergoes a multi-step crystallization reaction in the temperature range of 250-390 °C. The activation energies for the first exothermic reactions were determined as 344 kJ/mol. Instead of a primary crystallization, a eutectic reaction was found to be associated with the first reactions and the crystalline phases were identified as fcc-Al, Al11La3, Al3Ni and a metastable phase Al3La. The isothermal annealing was carried out at temperatures of 235 °C, 245 °C and 250 °C. Results from the isothermal annealing analyses revealed presence of quenched-in Al nuclei. The influence of isothermal annealing on the thermal stability of the Al85Ni10La5 powders (<25 μm) is also discussed.