COMPARISON OF SOLID-STATE AMORPHIZATION BY MECHANICAL ALLOYING AND INTERDIFFUSION IN NI-ZR

The amorphization process in mechanically alloyed Ni-Zr powders has been investigated by transmission electron microscopy, saturation magnetization measurements, and differential scanning calorimetry. The amorphous phase initially forms at the interface between the elemental layers produced during the early stages of milling. Longer processing results in fully amorphous material. Partially reacted powders show a similar microstructure and the same reaction steps during constant-rate heating as unreacted deformation-produced composites. This demonstrates the similarity of the reaction process for both preparation techniques. In particular, mechanical alloying prevents intermetallic phase formation during interdiffusion because of extremely thin layers, thus resulting in a wider glass-forming range than obtained by other preparation techniques based on solid-state interdiffusion.