Crystallization kinetics of Al–La–Ni amorphous alloy

Abstract

The crystallization kinetics of an Al 89La 6Ni 5 amorphous alloy were studied by thermal analysis. Both continuous heating and isothermal DSC traces showed that the Al 89La 6Ni 5 amorphous alloy undergoes a two-stage crystallization process upon heating. The first transformation, in which fcc-Al precipitates from the amorphous matrix, is a nucleation and three-dimensional diffusion-controlled growth process with an activation energy of 302 kJ/mol. The second transformation, in which the residual amorphous phase transforms into several intermetallic compounds, is a three-dimensional process with an activation energy of 300 kJ/mol. From the Kissinger method, different activation energies are obtained for the two transitions, 169 and 200 kJ/mol, respectively. The origin of this difference is discussed. It is supposed that the Kissinger activation energy includes the contribution of both the nucleation and growth activation energies and the activation energy derived from isothermal analysis comes mainly from growth.