UC Davis

Al85Ni10La5 (at.%) alloy powders were fabricated using gas atomization. X-ray diffraction analysis revealed that powders in the size range of < 500 mesh (< 25 mu m) are amorphous. The crystallization behavior and kinetics of the amorphous Al85Ni10La5 powders (< 25 mu m) 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 degrees 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 degrees C, 245 degrees C and 250 degrees 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 mu m) is also discussed. (c) 2005 Elsevier B.V. All rights reserved.