STP675: Persistent Slipbands in Fatigued Face-Centered and Body-Centered Cubic Metals

    Mughbrabi, H
    Research associate, doctorate student, and former doctorate student, Max-Planck-Institut für Metallforschung, Institut für PhysikStaatliche Material prüfungsanstalt, Universität Stuttgart, Stuttgart 80Stuttgart 80,

    Ackermann, F
    Research associate, doctorate student, and former doctorate student, Max-Planck-Institut für Metallforschung, Institut für PhysikStaatliche Material prüfungsanstalt, Universität Stuttgart, Stuttgart 80Stuttgart 80,

    Herz, K
    Research associate, doctorate student, and former doctorate student, Max-Planck-Institut für Metallforschung, Institut für PhysikStaatliche Material prüfungsanstalt, Universität Stuttgart, Stuttgart 80Stuttgart 80,

    Pages: 37    Published: Jan 1979


    Abstract

    The cyclic stress-strain response, the development of persistent slipbands (PSB's), and the related dislocation microstructures have been investigated on single crystals of face-centered-cubic (fee) copper, nickel, and silver and of body-centered-cubic (bee) α-iron and niobium at room temperature. The formation of PSB's as a bulk phenomenon appears to be a general feature in fee metal single crystals and can be described remarkably well in a simple model based largely on Winter's work. The present work clarifies and emphasizes the special roles of cross slip and of long-range internal stresses in the formation of the matrix structure, in the nucleation of PSB's, and in the steady-state deformation occurring in the PSB's. In pure bee metals, on the other hand, PSB's are not found to be a feature of comparable generality. Under typical testing conditions, cyclic deformation of bee metals occurs by the low-temperature deformation mode, characterized by the low mobility of the screw dislocations and impeded dislocation multiplication. However, a deformation mode similar to that in fee metals, accompanied in some cases by the formation of PSB's as a bulk feature, is found under special conditions: low strain rate, elevated temperature (below the regime of self-diffusion), and the presence of interstitial impurity atoms. In conclusion, some general requirements that appear essential to the development of PSB's in fatigued metals are formulated.

    Keywords:

    cyclic stress-strain response, fatigue, persistent slipbands, copper, nickel, silver, α, -iron, niobium, single crystals, dislocation microstructure, long-range internal stresses, cross slip, nucleation (of persistent slipbands), strain rate, interstitial impurities, dynamic strain aging, fatigue failure


    Paper ID: STP35885S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP35885S


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