The effect of coldwork on the Low Cycle Fatigue and Creep-Fatigue Interaction properties of Alloy D9

Alloy D9, a 15Cr-15Ni, Ti modified stainless steel is a candidate material for fast reactor core components due to its excellent resistance to void sw elling. The alloy with Ti/C ratio of 4 has been investigated For its Law Cy cle Fatigue(LCF) and Creep-Fatigue Interaction (CFI) properties in solution annealed and 20% cold worked condition. LCF tests have been conducted in a ir at 823K and 923K, while CFI tests were performed at 923K using holds at peak tensile strain. Under continuous cylcing LCF conditions, solution anne aled material exhibited superior LCF resistance than cold worked material a t both 823 and 923K, except at low strain ranges at 923K. The solution anne aled material underwent cyclic hardening while cold worked material display ed cyclic softening. Under CFI conditions, solution annealed material exhib ited a recovery in life at longer hold times, while coldworked material exh ibited a continuous decrease in life with increasing hold time. The LCF and CFI properties have been correlated with the substructural recovery and pr ecipitation at these temperatures.