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Probing size- and constituent-mediated mechanical properties and deformation behavior in crystalline/amorphous nanolaminates

Abstract

Two kinds of crystalline/amorphous nanolaminates (C/ANLs), i.e., Ag/Cu-Zr and Mo/Cu-Zr, with a wide range of modulation ratio η (thickness ratio of the amorphous layer to the crystalline layer) from 0.1 up to 9.0 were respectively prepared by using magnetron sputtering. Hardness and strain rate sensitivity m were measured for comparison through nanoindentation testing. The mechanical properties displayed a strong η-dependence, which was tuned by the crystalline phases. With increasing η, the hardness increased in the Ag/Cu-Zr nanolaminates while decreased in the Mo/Cu-Zr ones. However, the two C/ANLs showed similar variation in m that was reduced gradually from positive at small η to negative at large η. Microstructural examinations demonstrated that the amorphous Cu-Zr layers in both the C/ANLs appeared a deformation-induced crystallization (DIC) phenomenon within the nanoindentation deformation zone. The DIC was highly dependent on η and became more intense in the Mo/Cu-Zr than in the Ag/Cu-Zr C/ANLs. The η- and constituent-dependent DIC behaviors were rationalized in light of stress field applied on the amorphous layers that is sensitive to both the amorphous layer thickness and the crystalline constituent. This DIC-induced negative m in amorphous layers competed with the positive m in crystalline layers, leading to a negative-to-positive change in m with reducing η. The underlying deformation mechanisms were revealed to be a cooperation of dislocation activities in the crystalline layers and shear transformation zone motions in the amorphous layers. Furthermore, a modified mechanistic model was utilized to quantitatively describe the η-dependent hardness at different crystalline constituents.

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Publication details

The article was received on 02 Sep 2018, accepted on 30 Oct 2018 and first published on 30 Oct 2018


Article type: Paper
DOI: 10.1039/C8NR07129B
Citation: Nanoscale, 2018, Accepted Manuscript
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    Probing size- and constituent-mediated mechanical properties and deformation behavior in crystalline/amorphous nanolaminates

    Y. Wang, K. Wu, J.Y. Zhang, G. Liu and J. Sun, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR07129B

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