Multiaxial ratcheting of 20 carbon steel: Macroscopic experiments and microscopic observations

Journal Article · Sun Sep 15 04:00:00 EDT 2013 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2013.05.014· OSTI ID:22285073

Dong, Yawei ^[1]; Kang, Guozheng ^[1]; Liu, Yujie; Jiang, Han ^[2]

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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)

The multiaxial ratcheting behaviors of polycrystalline 20 ordinary carbon steel were investigated at room temperature. The macroscopic experimental results showed that the studied multiaxial ratcheting depends greatly on the mean stress, stress amplitude and loading path. The axial ratcheting strain increased with the increase of applied mean stress and stress amplitude. Apparent additional hardening was observed in the non-proportionally multiaxial cyclic loading. The multiaxial ratcheting of 20 carbon steel was lower than the corresponding uniaxial one and varies with different loading paths. Dislocation patterns and their evolutions of the multiaxial ratcheting of different loading paths were then investigated using transmission electron microscopy. The obtained images showed that, with the increasing number of loading cycles, the dislocation patterns evolved from dislocation lines and networks to dislocation tangles, walls and cells. After certain cycles, sub-grains were formed because of the re-arrangement of dislocations in the walls of cells and inside the cells since the cross slip of dislocations can be easily activated for the 20 carbon steel, a kind of body-centered cubic metal. The dislocation evolution of the multiaxial ratcheting is much quicker than that of the uniaxial one. With the reference to the uniaxial one of 20 carbon steel, the macroscopic multiaxial ratcheting behaviors can be qualitatively correlated with the microscopic observation of the dislocation patterns and their evolution. - Highlights: • Multiaxial loading hardly changes the cyclic stable feature of 20 carbon steel. • Multiaxial ratcheting of 20 carbon steel depends greatly on the load path. • Dislocation patterns evolve quicker in the multiaxial case. • The stabilized dislocation pattern is sub-grain, rather than the dislocation cell. • Sub-grains formed after certain cycles make the stable ratcheting strain rate large.

• OSTI ID: 22285073
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 83; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BCC LATTICES
CARBON STEELS
DISLOCATIONS
POLYCRYSTALS
RATCHETING
STRAIN RATE
STRESSES
TRANSMISSION ELECTRON MICROSCOPY