Cyclic deformation behavior of Ni3Nb single crystals deforming by slip on (010)[100]

Cyclic deformation behavior in Ni3Nb single crystals deforming by slip on ( 010)[100] was investigated. Fatigue tests were performed in a symmetrical p ush/pull mode at a fixed total strain amplitude (Delta epsilon) from +/-0.0 6 to +/-0.30% at ambient temperature. The cyclic hardening behavior varied below and above Delta epsilon = +/-0.15%. In the low strain amplitude group . the maximum stress amplitude reached a saturated value after initial stro ng hardening. while the cyclic hardening behavior in the high strain amplit ude group were divided into three stages including the initial strong harde ning. This initial strong hardening is related to the exhaustion hardening caused by the Kear-Wilsdorf locking. The hardening mechanism in each stage is discussed focusing on the cyclic stress-strain behavior, slip trace morp hology and dislocation structure, (C) 2001 Elsevier Science Ltd. All rights reserved.