Thermal rejuvenation in metallic glasses

• Published in: Science and technology of advanced materials Vol. 18; no. 1; pp. 152 - 162
• Main Authors: Saida, Junji, Yamada, Rui, Wakeda, Masato, Ogata, Shigenobu
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 01.01.2017; Taylor & Francis Ltd; Taylor & Francis Group
• Subjects: 10 Engineering and Structural materials; 106 Metallic materials; 302 Crystallization / Heat treatment / Crystal growth; 400 Modeling / Simulations; Amorphous materials; Annealing; Bonding strength; Cooling rate; Engineering and Structural Materials; Icosahedral phase; local structure; Low temperature; Mechanical properties; mechanical property; Metallic glass; Metallic glasses; molecular dynamics simulation; Parameters; Potential energy; Quenching; Recovery; rejuvenation; relaxation; Short range order; Tantalum; 106 Metallic materials; 400 Modeling / Simulations; local structure; 302 Crystallization / Heat treatment / Crystal growth; molecular dynamics simulation; relaxation; mechanical property; rejuvenation; 10 Engineering and Structural materials; Metallic glass
• ISSN: 1468-6996; 1878-5514
• DOI: 10.1080/14686996.2017.1280369

Structural rejuvenation in metallic glasses by a thermal process (i.e. through recovery annealing) was investigated experimentally and theoretically for various alloy compositions. An increase in the potential energy, a decrease in the density, and a change in the local structure as well as mechanical softening were observed after thermal rejuvenation. Two parameters, one related to the annealing temperature, T a /T g , and the other related to the cooling rate during the recovery annealing process, V c /V i , were proposed to evaluate the rejuvenation phenomena. A rejuvenation map was constructed using these two parameters. Since the thermal history of metallic glasses is reset above 1.2T g , accompanied by a change in the local structure, it is essential that the condition of T a /T g  ≥ 1.2 is satisfied during annealing. The glassy structure transforms into a more disordered state with the decomposition of icosahedral short-range order within this temperature range. Therefore, a new glassy structure (rejuvenation) depending on the subsequent quenching rate is generated. Partial rejuvenation also occurs in a Zr 55 Al 10 Ni 5 Cu 30 bulk metallic glass when annealing is performed at a low temperature (T a /T g ~ 1.07) followed by rapid cooling. This behavior probably originates from disordering in the weakly bonded (loosely packed) region. This study provides a novel approach to improving the mechanical properties of metallic glasses by controlling their glassy structure.