Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 833, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2021.142519
Keywords
Metallic glass; Nanocrystallization; Shear bands; Fracture toughness; Notch
Categories
Funding
- Australian Research Council [DP180101955]
- National Natural Science Foundation of China [51904243, 51974243]
- Postdoctoral Science Foundation of China [2019M653704]
- Young Talents Support Plan of Shaanxi Provincial College Association for Science and Technology [20200416]
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Micro-cantilever bending tests were conducted to study the fracture toughness and deformation mechanism of a Ti-based metallic glass. The results showed that plastic deformation was localized in shear bands initiated from the roots of the notches. The formation of shear bands and Cu nanocrystals were explained using the free volume theory and simulation results.
Micro-cantilever bending tests are performed to quantify the fracture toughness and reveal the deformation mechanism of a Ti-based metallic glass. Plastic deformation is localized in shear bands initiating from the roots of the notches of the cantilevers. Although the load-displacement curves show considerable ductile failure characteristics, the notch fracture toughness values that obtained from the bending tests are extremely low (similar to 4.7 MPa root m). Size dependent fracture is thought to be observed, where the fracture toughness increases with decreasing the uncracked ligament size of the cantilevers. TEM bright field images show that the shear bands with the width of 4-7 nm present brighter contrast. The regions in vicinity of the shear bands show dark zones (ranging from 3 to 5 nm in size) surrounded by continues bright zones. Cu nanocrystals are found not only inside the shear bands, but also around them. The free volume theory together with the simulation results is applied to explain the formation of shear bands in this Ti-based metallic glass during the bending deformation. The observed Cu nanocrystals are thought to be formed as a consequence of plastic-deformation-assisted crystallization. It is suggested that local atomic rearrangements lead to shifting of Cu nanocrystals towards more stable positions and cause the formation of Cu nanocrystals in regions subjected to high shear stress field.
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