Fig. 3. Cyclic stress-strain curves derived from TMF cycling tests with
and without dwell.
3.2. Microstructure
The initial microstructure of this Sanicro 25 alloy (i.e. after
annealing at 1200 °C for 1 h) has been studied earlier by Heczko et al.10, 11, 26 and Warner et al. 27. The
average grain size of 60 µm was determined by the intercept method;
however, large grains of the size up to 200 µm were present as well. The
characteristic attribute of dislocation structure before applying cyclic
loading is planar dislocation arrangement consisting of individual
dislocations, stacking faults, pile-ups etc. Heczko et al.10 reported the formation of large particles rich in
Nb and Cr identified as complex nitride (Cr,Nb)N i.e. Z-phase.