Nucleation and thickening of shear bands in nano-scale twin/matrix lamellae of a Cu-Al alloy processed by dynamic plastic deformation

C.S. Hong, N.R. Tao, Xiaoxu Huang, K. Lu

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Microstructural evolution associated with the shear banding in nano-scale twin/matrix (T/M) lamellae of a Cu–Al alloy processed by means of dynamic plastic deformation was investigated using transmission electron microscopy (TEM) and high-resolution TEM. The development of a shear band was found to be a two-stage process, namely a nucleation stage resulting in a narrow band composed of nano-sized (sub)grains intersecting the T/M lamellae, followed by a thickening stage of the narrow band into adjacent T/M lamellae regions. The nucleation stage occurred within a narrow region of an almost constant thickness (100–200 nm thick, referred to as “core” region) and consisted of three steps: (1) initiation of localized deformation (bending, necking, and detwinning) against the T/M lamellae, (2) evolution of a dislocation structure within the detwinned band, and (3) transformation of the detwinned dislocation structure (DDS) into a nano-sized (sub)grain structure (NGS). On the two sides of a core region, two transition layers (TRLs) exist where the T/M lamellae experienced much less shear strain. The interface boundaries separating the core region and the TRLs are characterized by very large shear strain gradients accommodated by high density of dislocations. Increasing shear strains leads to thickening of shear bands at the expense of the adjoining T/M lamellae, which is composed of thickening of the core region by transforming the TRLs into the core region with DDS and NGS, analogous to steps (2) and (3) of the nucleation process, and outward movement of the TRLs by deforming the adjoining T/M lamellae. Grain sizes in the well-developed shear bands are obviously larger than the lamellar thickness of original T/M lamellae.
    Original languageEnglish
    JournalActa Materialia
    Volume58
    Issue number8
    Pages (from-to)3103-3116
    ISSN1359-6454
    DOIs
    Publication statusPublished - 2010

    Keywords

    • Materials and energy storage
    • Light strong materials for energy purposes

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