Roles of grain boundaries in improving fracture toughness of ultrafine-grained metals

T. Shimokawa, M. Tanaka, K. Kinoshita, K. Higashida

    研究成果: Contribution to journalArticle査読

    38 被引用数 (Scopus)

    抄録

    In order to improve the fracture toughness in ultrafine-grained metals, we investigate the interactions among crack tips, dislocations, and grain boundaries in aluminum bicrystal models containing a crack and 112 tilt grain boundaries using molecular dynamics simulations. The results of previous computer simulations showed that grain refinement makes materials brittle if grain boundaries behave as obstacles to dislocation movement. However, it is actually well known that grain refinement increases fracture toughness of materials. Thus, the role of grain boundaries as dislocation sources should be essential to elucidate fracture phenomena in ultrafine-grained metals. A proposed mechanism to express the improved fracture toughness in ultrafine-grained metals is the disclination shielding effect on the crack tip mechanical field. Disclination shielding can be activated when two conditions are present. First, a transition of dislocation sources from crack tips to grain boundaries must occur. Second, the transformation of grain-boundary structure into a neighboring energetically stable boundary must occur as dislocations are emitted from the grain boundary. The disclination shielding effect becomes more pronounced as antishielding dislocations are continuously emitted from the grain boundary without dislocation emissions from crack tips, and then ultrafine-grained metals can sustain large plastic deformation without fracture with the drastic increase of the mobile dislocation density. Consequently, it can be expected that the disclination shielding effect can improve the fracture toughness in ultrafine-grained metals.

    本文言語英語
    論文番号214113
    ジャーナルPhysical Review B - Condensed Matter and Materials Physics
    83
    21
    DOI
    出版ステータス出版済み - 6 30 2011

    All Science Journal Classification (ASJC) codes

    • 電子材料、光学材料、および磁性材料
    • 凝縮系物理学

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