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.