Constant-load-amplitude stage II fatigue crack growth rates at 4 K were measured for duplex stainless steel castings. The results show that at a ΔK of 60 MPa•m1/2, da/dN = 7.6 × 10−4 mm/cycle for an alloy with 1 percent ferrite. For an alloy with 8 percent ferrite, da/dN is 35 percent, and for an alloy with 29 percent ferrite, da/dN is 260 percent greater than for the 1 percent ferrite alloy. However, the exponent in the Paris equation does not change appreciably (less than 18 percent) as the ferrite content changes from 1 to 29 percent.

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