Solid-state crystalline-glassy cyclic phase transformations of mechanically alloyed Cu33Zr67 powders

Cyclic crystalline-glassy-crystal line phase transformations have been investigated during high-energy ball milling of elemental CU(33)ZF(67) powders under an argon gas atmosphere. The results show that the metallic glass, which is obtained after 86 ks of milling time, transforms into a new metastable phase of nanocrystalline fee CuZr2 upon milling for 173 ks. It subsequently transforms to the same glassy phase after 259 ks of the milling time. Such cyclic phase transformations are observed several times during the milling. The present work shows that this phenomenon does not have any obvious analogues with the periodic redox reactions or with diffusive-reactive phenomena known in chemistry. On the basis of our results, the destabilizing effect of the defects created by the milling media (balls), which leads to the cyclic transformations, depends not only on the milling time but also on the milling rotation speed.