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Title: Macroscopic and microscopic investigations on uniaxial ratchetting of two-phase Ti–6Al–4V alloy

Abstract

The uniaxial ratchetting of Ti–6Al–4V alloy with two phases (i.e., primary hexagonal close packed (HCP) α and secondary body-centered cubic (BCC) β phases) was investigated by macroscopic and microscopic experiments at room temperature. Firstly, the effects of cyclic softening/hardening feature, applied mean stress and stress amplitude on the uniaxial ratchetting of the alloy were discussed. The macroscopic investigation of Ti–6Al–4V alloy presents obvious strain-amplitude-dependent cyclic softening, as well as a three-staged evolution curve with regard to the ratchetting strain rate. The ratchetting depends greatly on the applied mean stress and stress amplitude while the ratchetting strain increases with the increasing applied mean stress and stress amplitude. Then, the evolution of dislocation patterns and deformation twinning during the uniaxial ratchetting of two-phase Ti–6Al–4V alloy were observed using transmission electron microscopy (TEM). The microscopic observation shows that deformation twinning occurs in the primary α phase and its amount increases gradually during the uniaxial ratchetting. Simultaneously, the planar dislocation evolves from discrete lines to some dislocation nets and parallel lines with the increasing number of cycles. The deformation twinning in the primary α phase is one of main contributions to the uniaxial ratchetting of Ti–6Al–4V alloy, and should be considered in the constructionmore » of corresponding constitutive model. - Highlights: • A three-staged ratchetting occurs in the stress-controlled cyclic tests of Ti–6Al–4V alloy. • Dislocation patterns change from discrete lines to nets and parallel lines. • Deformation twinning occurs during the uniaxial ratchetting. • Both dislocation slipping and twinning are the causes of ratchetting.« less

Authors:
 [1]; ; ;  [2]
  1. State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031 (China)
  2. School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)
Publication Date:
OSTI Identifier:
22340364
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 92; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; AMPLITUDES; BCC LATTICES; DEFORMATION; DISLOCATIONS; HARDENING; HCP LATTICES; STRAIN RATE; STRESSES; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Kang, Guozheng, E-mail: guozhengkang@home.swjtu.edu.cn, Dong, Yawei, Liu, Yujie, and Jiang, Han. Macroscopic and microscopic investigations on uniaxial ratchetting of two-phase Ti–6Al–4V alloy. United States: N. p., 2014. Web. doi:10.1016/J.MATCHAR.2014.02.014.
Kang, Guozheng, E-mail: guozhengkang@home.swjtu.edu.cn, Dong, Yawei, Liu, Yujie, & Jiang, Han. Macroscopic and microscopic investigations on uniaxial ratchetting of two-phase Ti–6Al–4V alloy. United States. doi:10.1016/J.MATCHAR.2014.02.014.
Kang, Guozheng, E-mail: guozhengkang@home.swjtu.edu.cn, Dong, Yawei, Liu, Yujie, and Jiang, Han. 2014. "Macroscopic and microscopic investigations on uniaxial ratchetting of two-phase Ti–6Al–4V alloy". United States. doi:10.1016/J.MATCHAR.2014.02.014.
@article{osti_22340364,
title = {Macroscopic and microscopic investigations on uniaxial ratchetting of two-phase Ti–6Al–4V alloy},
author = {Kang, Guozheng, E-mail: guozhengkang@home.swjtu.edu.cn and Dong, Yawei and Liu, Yujie and Jiang, Han},
abstractNote = {The uniaxial ratchetting of Ti–6Al–4V alloy with two phases (i.e., primary hexagonal close packed (HCP) α and secondary body-centered cubic (BCC) β phases) was investigated by macroscopic and microscopic experiments at room temperature. Firstly, the effects of cyclic softening/hardening feature, applied mean stress and stress amplitude on the uniaxial ratchetting of the alloy were discussed. The macroscopic investigation of Ti–6Al–4V alloy presents obvious strain-amplitude-dependent cyclic softening, as well as a three-staged evolution curve with regard to the ratchetting strain rate. The ratchetting depends greatly on the applied mean stress and stress amplitude while the ratchetting strain increases with the increasing applied mean stress and stress amplitude. Then, the evolution of dislocation patterns and deformation twinning during the uniaxial ratchetting of two-phase Ti–6Al–4V alloy were observed using transmission electron microscopy (TEM). The microscopic observation shows that deformation twinning occurs in the primary α phase and its amount increases gradually during the uniaxial ratchetting. Simultaneously, the planar dislocation evolves from discrete lines to some dislocation nets and parallel lines with the increasing number of cycles. The deformation twinning in the primary α phase is one of main contributions to the uniaxial ratchetting of Ti–6Al–4V alloy, and should be considered in the construction of corresponding constitutive model. - Highlights: • A three-staged ratchetting occurs in the stress-controlled cyclic tests of Ti–6Al–4V alloy. • Dislocation patterns change from discrete lines to nets and parallel lines. • Deformation twinning occurs during the uniaxial ratchetting. • Both dislocation slipping and twinning are the causes of ratchetting.},
doi = {10.1016/J.MATCHAR.2014.02.014},
journal = {Materials Characterization},
number = ,
volume = 92,
place = {United States},
year = 2014,
month = 6
}
  • Uniaxial ratchetting characteristics of 316FR steel at room temperature are studied experimentally. Cyclic tension tests, in which maximum strain increases every cycle by prescribed amounts, are conducted systematically in addition to conventional monotonic, cyclic, and ratchetting texts. Thus hysteresis loop closure, cyclic hardening and viscoplasticity are discussed in the context of constitutive modeling for ratchetting. The cyclic tension tests reveal that very slight opening of hysteresis loops occurs, and that neither accumulated plastic strain nor maximum plastic strain induces significant isotropic hardening if strain range is relatively small. These findings are used to discuss the ratchetting tests. It is thusmore » shown that uniaxial ratchetting of the material at room temperature is brought about by slight opening of hysteresis loops as well as by viscoplasticity, and that kinematic hardening governs almost all strain hardening in uniaxial ratchetting if stress range is not large.« less
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