Grain-size effect on plastic flow stress of nanolaminated polycrystalline aluminum/graphene composites. (September 2020)

• Record Type: Journal Article
• Authors: Zhou, Xiaohuan; Liu, Xia; Shang, Junjun; Yang, Qingsheng
• Is Part Of: Mechanics of materials. Volume 148(2020)
• Publication Date: 2020-09
• Subjects: Aluminum/graphene composites -- Plastic flow -- Grain-size effect -- Dislocation evolution -- Molecular dynamics simulation; Strength of materials -- Periodicals; Mechanics, Applied -- Periodicals; Résistance des matériaux -- Périodiques; Mécanique appliquée -- Périodiques; Mechanics, Applied; Strength of materials; Periodicals; Electronic journals; 620.11
• DOI: 10.1016/j.mechmat.2020.103530
• Languages: English
• ISSNs: 0167-6636

Abstract

Highlights: Extended dislocations dominate the plastic deformation of nanolaminated PAl/Gr composites. The dislocation-GB interaction transits to a dislocation-Gr interaction with the decreasing of laminate thickness. The greater ability of storing dislocations at the interface contributes to the strain-hardening capability. The back-stress strengthening mechanism is induced by GNDs to accommodate the deformation gradient. A CLS model considering back-stress strengthening can accurately predict the flow stress of PAl/Gr composites. Abstract: Nanolaminated metal/graphene composites can have many special mechanical properties, thanks to a high density of interfaces. Even though the interface effect is a key mechanism for the propagation of dislocations in nanolaminated metal/graphene composites, it is not well understood. In this paper, simulations of the molecular dynamics of nanolaminated polycrystalline aluminum/graphene (PAl/Gr) composites are performed. The results provide insight into the grain-size effect on plastic flow stress of nanolaminated PAl/Gr composites and the underlying mechanism. Extended dislocations are found to dominate the plastic deformation of the PAl/Gr composites. Both the PAl/Gr interface and the Al grain boundaries (GBs) interact with the dislocations. Three dislocation propagation forms are observed in the PAl/Gr nanolaminated composite based on the Al grain-size. By decreasing the laminate thickness, the dislocation-GB interaction can transition to a dislocation-graphene interaction. When the Al layer thickness is smaller than the in-plane grain size, the strain-hardening capability is increased due to greater ability of the dislocation/graphene-interface to store dislocations than the GBs. Besides, geometrically necessary dislocations are induced because of the deformation gradient between the graphene and Al grains, which lead to back-stress strengthening and thus strain hardening. Accordingly, a confined layer slip mechanism, which considers back-stress, is used to predict the flow stress of the PAl/Gr composites.