Orientation-Dependent Tensile Behavior of Nanolaminated Graphene-Al Composites: An In Situ Study
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e attainment of metal matrix composites (MMCs) with desired mechanical properties relies on the deliberate control over the microstructural features of the composite, including the matrix grain size, the type, size, and distribution of the reinforcement, and the nature of the reinforcement/matrix interface.[1–3] The development of conventional MMCs is guided by the design principle of homogeneous dispersion of reinforcements. Despite
XIDAN FU, ZAN LI, QIANG GUO, GENLIAN FAN, ZHIQIANG LI, DING-BANG XIONG, ZHANQIU TAN, YISHI SU, and DI ZHANG are with the State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China. Contact e-mails: [email protected] and [email protected] SHMUEL OSOVSKI is with the Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel. Manuscript submitted April 2, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
the many enhanced properties, such as strength, stiffness, and wear resistance that may be achieved, however, such a strategy usually leads to a sacrifice in the ductility and toughness of the composite, which is an inherent setback that greatly limits the engineering application of these composites. On comparison, biological hard materials, represented by nacre, tooth, and bone, are naturally composite materials. Although constituted by constituents that generally exhibit poor macroscale mechanical properties, such as soft proteins and brittle minerals, these materials show simultaneous improvement in strength and toughness over the composites consisting of the same components.[4,5] This remarkable mechanical property synergy in biological hard materials is considered to mainly result from their delicate microstructures.[6–8] Therefore, designing and fabricating artificial MMCs with a bioinspired microstructure is a potential way to achieve a balanced mechanical property to mitigate the strength-toughness/ ductility conflict. Recently, we developed graphene [reduced graphene oxide (RGO)]–reinforced Al matrix composite with a bioinspired nanolaminated microstructure, and tensile tests revealed that the composite is both stronger and tougher than the pure Al matrix fabricated by the same approach.[9] This significant strengthening and toughening effect was rationalized in terms of the effective load transfer between RGO and the Al matrix as a result of the robust RGO/Al interface and a crack deflection and bridging mechanism derived from the nanolaminated structure.[9,10] However, the directional arrangement of RGO in the bulk nanolaminated RGO-Al composites naturally leads to the following questions: (1) Is the tensile behavior of the RGO-Al composites orientation dependent? If this is true, (2) what is the mechanism that is responsible for the anisotropy? In this work, we report the orientation-dependent mechanical behavior of the RGO-Al nanolaminated composite using an in situ uniaxial tensile test on composite micropillars conducted in a scanning electron microscope (SEM). Specifically, we studied the effects of
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