ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Plastic Deformation Behaviour and Substructure in CoTi Single Crystals Fatigued at Room Temperature
Ahmad BehgozinTakayoshi NakanoYukichi Umakoshi
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1997 Volume 37 Issue 12 Pages 1218-1223

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Abstract

Cyclic deformation and deformation substructure of CoTi single crystals were examined focusing on operative slip systems and cyclic hardening. Fatigue tests were performed in a tension/compression mode under a fixed amplitude of total strain (Δε=±0.1-±0.3 %) in air at room temperature. CoTi deformed by {110}<001> slips at various strain amplitudes. At Δε=±0.1 % primary (110)[001] slip was dominant and the stress amplitude gradually increased with number of cycles until it reached a saturated value. As secondary slips were more activated with increasing Δε, cyclic hardening was more accelerated and the fatigue life was shortened. Highly piled-up dislocations composed of primary and secondary dislocations formed strong residual stress fields, resulting in crack initiation and propagation. A large number of dipoles and loops which also contributed to cyclic hardening were produced during the to-and-fro motion of <001> screw dislocations.

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