Deformation and fracture behavior of a directionally solidified Ni3Al alloy

Dongliang Lin(T.L. Lin), Yun Zhang, Mingwei Chen, Hui Lin

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    The {111} slip behavior of a directionally solidified (DS) Ni3AlZrB alloy has been investigated in tension in the temperature range of 773-1373 K, and in-situ transmission electron microscope (TEM) observation of the fracture behavior of the same alloy has also been carried out. The dependence of deformation rate on yield stress (at 0.2% plastic strain) is found to be exponential above the peak temperature. The dependence of deformation rate on flow stress (at 3.8% plastic strain) obeys a power-law relation above the peak temperature, with the stress exponent n = 4.89 in the temperature range of 1073-1173 K, suggesting a deformation mechanism of edge dislocation climb, and n = 2.70 in the temperature range of 1273-1373 K, suggesting a deformation mechanism of viscous screw dislocation glide. The dislocation structure develops with increasing stress and strain, the dislocation density ρ is related to the applied stress σ as ρ σ σ1.7, and no steady-state dislocation density is achieved up to 3.8% strain. With increasing temperature, the activation volume decreases below the peak temperature, and stays constant at a low level above the peak temperature, reflecting two different processes of thermal activation or unpinning of the Kear-Wilsdorf (KW) locks. Room-temperature in-situ TEM straining tests revealed that, near a crack tip edge, dislocations glide away quickly and leave behind many long straight screw dislocations pinned by the KW locks. The large number of pinned screw dislocations reduce the mobility of dislocations and induce cleavage fracture. Additionally, for the first time, an athermal unpinning process has been observed for screw dislocations around a crack tip.

    Original languageEnglish
    Pages (from-to)647-657
    Number of pages11
    JournalMaterials Science and Engineering A
    Volume192-193
    Issue numberPART 2
    DOIs
    Publication statusPublished - 1995 Feb 28

    Keywords

    • Alloys
    • Aluminium
    • Deformation
    • Fracture
    • Nickel

    ASJC Scopus subject areas

    • Materials Science(all)
    • Condensed Matter Physics
    • Mechanics of Materials
    • Mechanical Engineering

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