The ductility and toughness improvement in metallic glass through the dual effects of graphene interface
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Chuang Denga) Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
Mahmoud Shariati Department of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Rzzavi Khorasan 91779-48974, Iran
Hossein Tavakoli-Anbaran Faculty of Physics, Shahrood University of Technology, Shahrood, Semnan 36155-316, Iran (Received 3 October 2016; accepted 23 November 2016)
Bulk metallic glasses own unique mechanical properties such as high strength and excellent elastic behavior due to their amorphous atomic structure. Nonetheless, they usually fail catastrophically by shear localization without showing any macroscale plastic deformation under tension and therefore are notoriously brittle. In this study, graphene was proposed as an effective reinforcement to improve the ductility and toughness of metallic glass for possessing a unique combination of strong in-plane strength and weak interbonding with the metal matrix based on molecular dynamics simulations. Both continuous and discontinuous graphene sheets with various configurations and lengths were taken into account. It was found that with proper dispersion of the graphene reinforcements, more than 100% increase in the ductility and more than 150% increase in the toughness can be achieved in the nanocomposites as compared to the monolithic metallic glass of similar size, which was enabled by spreading and delocalizing the plastic shearing deformation in the nanocomposites because of the dual effects of the added graphene.
I. INTRODUCTION
Bulk metallic glasses (BMGs) have attracted dramatic attention in the materials science community due to their extraordinary properties; e.g., their amorphous atomic structure gives rise to distinctive mechanical properties such as high fracture strength, high hardness, and large elastic strain limit in contrast to common engineering materials.1–4 However, BMGs usually fail catastrophically without any macroscale plastic deformation due to fast propagation of a major shear band.5,6 Therefore, many efforts have been carried out to reinforce and improve the ductility and toughness of BMGs during the last decade.3,7–9 Since shear bands play a central role in plastic behaviors of BMGs, it has been widely accepted that the plasticity of BMGs can be improved by introducing heterogeneity to arrest the propagation10 or delocalize the formation of shear bands.3,11 In this regard, introducing second phases has been used as a common technique to reinforce and improve the ductility or toughness of glassy materials.9–20 The most Contributing Editor: Jörg F. Löffler a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.479
commonly used approach is to produce a microstructural composite of amorphous matrix embedded with crystalline particles or dendrites. The second crystalline phase may act as initiation sites for shear band forming and therefore increase the number of shear bands throughout the specimen.9 For example, partial crystallization
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