The Study of Fatigue Behaviors and Dislocation Structures in Interstitial-Free Steel

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2010-08, Vol.41 (8), p.1995-2001
• Main Authors: Shih, Chia-Chang, Ho, New-Jin, Huang, Hsing-Lu
• Format: Article
• Language: English
• Subjects: Applied sciences; Behavior; Characterization and Evaluation of Materials; Chemistry and Materials Science; Crack initiation; Exact sciences and technology; Fatigue; Materials Science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metal fatigue; Metallic Materials; Metals. Metallurgy; Nanotechnology; Structural Materials; Surfaces and Interfaces; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-010-0186-6

There are three types of cyclic hardening for cyclically deformed interstitial-free (IF) steels. The magnitude of cyclic hardening was unobvious and dislocation cells smaller than 2  μ m were very hard to find when total strain amplitude (Δ ε /2) was controlled to within 0.1 pct. When Δ ε /2 is increased to 0.125 to 0.3 pct, secondary cyclic hardening takes place prior to fatigue failure. Δ ε /2 = 0.6 pct, following an initial rapid-hardening stage. Dislocation cells smaller than 2  μ m tend to develop near grain boundaries and triple junction of the grains while cycling just above Δ ε /2 = 0.125 pct. Such dislocation development results in secondary hardening. However, no failure occurs if cycling just below Δ ε /2 = 0.1 pct; hence, the fatigue limit for IF steel should be very close to Δ ε /2 = 0.1 pct.