Thermodynamic Evaluation of Irreversible Amorphization in W-Containing Metallic Glass Composite

Alloy powders containing nano-crystalline W distributed within an amorphous matrix were synthesized by high-energy ball milling. When the powder samples were heated to above the crystallization temperature, most of the amorphous phase retained within the initial powders were fully crystallized to metastable M₆C. As the heating temperature was further increased, an amorphous phase was formed accompanying the decomposition of the M₆C phase. In particular, the amorphous phase newly formed upon heating was maintained even after cyclic heating at high temperature. These findings showing the irreversible amorphization will be discussed in the aspect of the energetic difference between amorphous and its alternative phase, considering carbon diffusion within the alloy powders.