Effect of strain rate on the tensile properties of irradiated Inconel 718

The effects of strain rate on the elevated temperature tensile properties of unirradiated and irradiated Inconel 718 were determined. Irradiation conditions included total neutron fluences to 1.0 x 1022 n/cm2 at 4000C, to 2.4 x 1022 n/cm2 at 5930C, and 3.4 x 1022 n/cm2 at 6490C. Test parameters included temperatures to 6490C and strain rates to 1.0 sec-1. Results show that the strength and ductility of unirradiated Inconel 718 are insensitive to strain rate for temperatures to 5380C. At higher temperatures above 5380C both properties significantly increased with strain rate. Neutron irradiation at approximately 4000C did not alter this behavior since postirradiation properties were essentially unaffected by increasing strain rate. At irradiation temperatures of 5930C and above, strength properties were essentially consistent with unirradiated behavior. Ductility parameters were unaffected by strain rate for temperatures to 5380C. At higher temperatures ductility increased significantly with strain rate and approached unirradiated values. The severe ductility losses observed in all irradiated specimens at the lowest test rate (3 x 10-5 s-1) and higher test temperatures (5930C and above) are believed to result from helium embrittlement