Low cycle fatigue behaviour of a ferritic steel strengthened with nano-meter sized precipitates

Publication date: Available online 14 April 2019Source: Materials Science and Engineering: AAuthor(s): S. Majumdar, A.D. Gandhi, M.S. BishtAbstractLow-cycle-fatigue behaviour (Δεt/2 = ± 0.002 to ± 0.01) of a ferritic-steel (tensile strength ∼ 800 MPa) strengthened with nano-meter-sized-precipitates has been examined. The selected steel is a hot-rolled Ti-Mo-bearing low-carbon steel (grain size ∼ 3 μm) strengthened predominantly with Ti-Mo-C and Ti-C type precipitates of size ≤ 30 nm distributed randomly on the grain-boundaries and the matrix.The spread of cyclic-plasticity is negligible in the steel till Δεt/2 = 0.0025 leading to cyclically-stable behaviour and excellent fatigue-life (no failure till 105 loading cycles). At Δεt/2 = 0.003, significant initial-cyclic-hardening is noticed followed by minor amount of cyclic-softening. The latter is attributed to formation of low-energy-dislocation-structures e.g. dislocation-walls and channels. At Δεt/2 = 0.004–0.01, predominantly cyclic-hardening is noticed till failure; the intensity of hardening increases with increase in Δεt/2. The cyclic-hardening is attributed to increase in dislocation-density and dislocation-precipitate-interaction, formation of subgrains, microbands and dislocation-clusters within both ferrite-grains and microbands. All the above types of dislocation-substructures hinder movement of dislocations and reduce opportunity for cyclic-strain-hardening at...
Source: Materials Science and Engineering: A - Category: Materials Science Source Type: research