Thermal rejuvenation in metallic glasses. Issue 1 (31st December 2017)

• Record Type: Journal Article
• Authors: Saida, Junji; Yamada, Rui; Wakeda, Masato; Ogata, Shigenobu
• Is Part Of: Science and technology of advanced materials. Volume 18:Issue 1(2017)
• Page Start: 152
• Page End: 162
• Publication Date: 2017-12-31
• Subjects: Metallic glass -- rejuvenation -- relaxation -- molecular dynamics simulation -- mechanical property -- local structure; 10 Engineering and Structural materials -- 106 Metallic materials -- 302 Crystallization / Heat treatment / Crystal growth -- 400 Modeling / Simulations; Materials -- Technological innovations -- Periodicals; 620.112
• DOI: 10.1080/14686996.2017.1280369
• Languages: English
• ISSNs: 1468-6996

Abstract

Abstract: 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 1.2 T 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 Zr55 Al10 Ni5 Cu30 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. Abstract :