Microstructure associated with crack initiation during low-cycle fatigue in a low nitrogen duplex stainless steel

Fatigue crack initiation behavior in embrittled austenitic–ferritic stainless steel

“…Formation of slip markings along the {1 1 1} slip plane resulting from cyclic plastic irreversibility at the beginning of cyclic loading is a common observation (Refs. [4,7,8]). Accounting for a very low plastic strain being accommodated in the slip bands in the austenite grains, no appreciable elastic stress concentration at the boundaries (TB, GB) in the form of activation of slip systems in embrittled ferritic grains was noticed in the first interruption of this fatigue test.…”

“…The low cycle and high cycle fatigue behavior of DSSs in ambient air, corrosive environment and at high temperature were studied extensively [1][2][3]. In recent years progress was made in understanding the fatigue crack initiation behavior in low cycle fatigue (LCF) and high cycle fatigue (HCF) regimes in DSSs [4][5][6][7][8][9][10]. This has assumed significance as microstructure based fatigue life prediction is widely attempted for a number of metallic alloys for accuracy and better predictability.…”

“…In DSSs the presence of two phases affects the evolution of surface roughness, subsequent nucleation and growth of short fatigue cracks during cyclic loading [7][8][9]. Therefore, the fatigue crack initiation behavior in DSS is strongly influenced by the microstructural parameters such as grain size and grain orientation, grain and phase boundary geometry, i.e.…”

“…grain boundary character distribution, and precipitation condition [4]. The fatigue crack initiation and growth in a particular grain in DSS also depend on the orientation, inherent strength and toughness properties of neighboring grains, and it is very important to know and understand how these factors determine the fatigue damage evolution [7]. The fatigue damage evolution in DSSs is further complicated when the material is aged at 475°C and the difference in the mechanical properties of austenite and ferrite becomes more pronounced [10,11].…”

Cyclic Deformation of Advanced High-Strength Steels: Mechanical Behavior and Microstructural Analysis

“…However, the formation of a cell or subgrain structure was not observed after testing as it was for the DP steel. This lack of cell formation could be explained by the larger ferrite grain size of the DP steel, as in larger grains a larger plastic activity could be developed, [25] or alternatively by the lower plastic strain component for a given strain amplitude in the TRIP steel due to a higher yield stress (this mechanism is discussed further in Section III-F-1). The retained austenite crystals did not show deformation twins (Figure 11(b)) and the volume fraction of retained austenite in the microstructure was similar to that observed in the as-received conditions.…”