Influence of Dynamic Strain Aging on High Cycle Fatigue Behavior of Alloy 617M

Effect of dynamic strain aging (DSA) on the high cycle fatigue (HCF) behavior of alloy 617M was evaluated at ambient temperature and 923 K. The material showed finite cyclic lives at stresses below the yield stress (YS) at ambient temperature. However, tests conducted at 923 K which distinctly falls under the DSA regime, led to run-out (107 cycles) at stresses below and at YS. Experimental results also indicated that fatigue limit (based on run-out at 107 cycles) exceeded the YS at 923 K. This indicates that under HCF loading, fatigue failure is suppressed under the influence of DSA which in turn shifts the window of finite lives to higher stresses even above YS.