CRYSTALLIZATION KINETICS OF AMORPHOUS CU-NI-P ALLOYS

The nucleation and growth kinetics of the initial stages of primary and eutectic crystallization in amorphous, melt spun, near eutectic Cu-Ni-P alloys were studied by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Depending upon the composition, the reaction sequence is either (a) primary crystallization of faulted, f.c.c. copper, followed by eutectic precipitation of copper and a hexagonal phase ("hex-(Cu,Ni)3P") or (b) primary crystallization of hex-(Cu,Ni)3P and simultaneous growth of quenched-in nuclei of a trigonal phase ("trig-(Cu,Ni)3P"), followed by a eutectic of this phase with copper. In both primary precipitation reactions transient nucleation and diffusion-controlled growth of the particles were observed. The Cu+trig-(Cu,Ni)3P eutectic showed linear growth. The activation energies of the processes governing the incubation times, nucleation processes and growth rates were determined from the temperature dependence of these parameters.