Tuning nanoscale heterogeneity by non-affine thermal strain to modulate defect activation and maximize magnetocaloric effect of metallic glass

• Published in: Materials & design 2023-01, Vol.225, p.111500, Article 111500
• Main Authors: Luo, Qiang, Cui, Jingxian, Zhang, Zhengguo, Han, Minhao, Shen, Baolong
• Format: Article
• Language: English
• Subjects: Magnetocaloric effect; Metallic glasses; Relaxation spectrum; Structural heterogeneity
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2022.111500

[Display omitted] •Rejuvenation, increased structure order, and nanocrystallization induced by proper cryogenic thermal cycling are observed.•Two kinds of flow defects with different relaxation times are detected by using the Maxwell-Voigt model.•An apparent enhancement of the maximum magnetic entropy change from 9.5 to 10.7 JKg-1K−1 under 5 T is obtained.•A power law between the peak temperature and maximum magnetic entropy change is revealed above 85 K. The effects of non-affine thermal strain on the structure, defect activation and magnetocaloric effect (MCE) have been investigated in Gd55Co20Al24.5Si0.5 metallic glass (MG). Maxwell-Voigt models are utilized to analyze the impact of cryogenic thermal cycling (CTC) on the evolution of heterogeneous structure in term of the activated defects during creep deformation. Two kinds of flow defects with different relaxation times are observed from the relaxation spectrum, which show different responses to CTC. A power law between the maximum magnetic entropy change and its peak temperature is uncovered for Gd-based MGs above 85 K, which breaks down below 85 K for the low Gd content MGs including the high-entropy MGs. Through adjusting the CTC number, the maximum magnetic entropy of the present MG is improved to 10.7 JKg-1K−1 under 5 T, which is the largest among the Gd-based MGs with Curie temperature above 85 K. The enhancement of MCE is related to the increased fraction of solid-like zones in the amorphous matrix and nanocrystallization rendered by CTC treatment. This work sheds new insights into the correlation of MCE and nanoscale creep deformation with structural heterogeneity of MGs.