Fatigue behavior of nanoscale Mo/W multilayers on flexible substrates
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.252
Fatigue behavior of nanoscale Mo/W multilayers on flexible substrates Fang Wang1,2, Xue-Mei Luo1,*, Dong Wang3, Peter Schaaf3, Guang-Ping Zhang1,* 1Shenyang
National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China
2School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China
3Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano®, TU Ilmenau, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau, Germany
ABSTRACT
Fatigue properties of Mo/W multilayers with individual layer thickness (λ) of 5, 20, 50 and 100 nm on flexible polyimide substrates were investigated. The experimental results show that the fatigue resistance increases with decreasing λ from 100 nm to 20 nm, and reaches the maximum at λ=20 nm, and then decreases when further decreasing λ. Fatigue cracks of Mo/W multilayers with different λ were found to propagate along columnar grain boundary in the out-of-plane direction and along the boundary of cluster structures. The enhanced fatigue resistance is attributed to the larger cluster inclination angles and the more tortuous in-plane cracking paths.
INTRODUCTION Metallic multilayered composites consisting of alternating two or more components and heterogeneous interfaces at the nanometer scale have shown extraordinary mechanical and physical properties including ultra-high strength, * Corresponding authors. E-mails: [email protected], [email protected]
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good electrical, magnetic and optical properties, and superior irradiation resistance, etc. [1]. The nanoscale multilayered composites have been widely used in very large-scale integration of circuits, flexible electronics, and micro/nano-electromechanical systems (MEMS/NEMS) [2-6]. Generally, these systems may be subjected to cyclic loading during manufacturing and daily service. Thus, an understanding of fatigue behavior of the nanoscale multilayers under cyclic loading is a key to build high-performance and long-term reliable systems. Owing to the high crack growth resistance from layer interfaces, the fatigue strength of bulk laminated composites is found to be higher than that of their components [7-10]. Wang et al. [11] found that the stress to failure of nanoscale self-supported Cu/Nb multilayers with fcc/bcc layer interfaces was an order of magnitude increase of fatigue strength, compared with the bulk Cu. Zhu et al. [12] showed that the fatigue strength of Cu/Ni multilayers on polyimide substrates with fcc/fcc layer interfaces increased with the decrease in individual layer thickness (λ), and reached the maximum when λ=20 nm. In this study, fatigue properties of nanoscale Mo/W mult
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