Structural evolution and property changes in Nd60Al10Fe20Co10 bulk metallic glass during crystallization

The structural evolution and property changes in ${\mathrm{Nd}}_{60}{\mathrm{Al}}_{10}{\mathrm{Fe}}_{20}{\mathrm{Co}}_{10}$ bulk metallic glass (BMG) upon crystallization are investigated by the ultrasonic method, x-ray diffraction, density measurement, and differential scanning calorimetry. The elastic constants and Debye temperature of the BMG are obtained as a function of annealing temperature. Anomalous changes in ultrasonic velocities, elastic constants, and density are observed between 600–750 K, corresponding to the formation of metastable phases as an intermediate product in the crystallization process. The changes in acoustic velocities, elastic constants, density, and Debye temperature of the BMG relative to its fully crystallized state are much smaller, compared with those of other known BMGs, the differences being attributed to the microstructural feature of the BMG.