Cyclic plasticity of nickel at low plastic strain amplitude: hysteresis loop shape analysis

The cyclic plasticity of nickel was studied by accomplishing room temperatu re fully-reversed fatigue experiments at constant plastic strain amplitudes of 1.0 x 10(-4) and 2.5 x 10(-4) on single crystal and polycrystal nickel with 290 mum grain size. The cyclic plasticity behavior within a hysteresis loop was analyzed by measuring shape characteristics of the loop. Paramete rs that were evaluated include the loop shape parameter, friction stress, b ack stress, and second derivative of stress with respect to total strain. R esults indicate that these parameters correlate well with the development o f dislocation substructures. In addition, at low plastic strain amplitude. polycrystal and single crystal hysteresis loops exhibit a distinct constric tion. The constriction is more pronounced in single crystals cycled at the lower plastic strain amplitude. (C) 2001 Elsevier Science B.V. All rights r eserved.