Effects of irradiation on the fracture toughness of Alloy 718 plate and weld
The effect of fast-neutron irradiation on the J/sub Ic/ fracture toughness of Alloy 718 plate and weld was characterized at 427/sup 0/C using single- and multiple-specimen R-curve techniques. Two heat treatments were employed: the conventional ASTM B637 precipitation heat treatment (CHT) and a modified heat treatment (MHT) designed to improve the impact toughness of Alloy 718 welds. In the unirradiated and irradiated conditions, the fracture resistance of the MHT materials was consistently higher than that for their CHT counterparts. Irradiation significantly reduced the J/sub Ic/ and tearing modulus values for the plate and weld in both heat-treated conditions with saturation occurring at relatively low neutron exposures (below 8 dpa). The CHT base metal and weld exhibited saturation J/sub Ic/ levels of 31 and 21 kJ/m/sup 2/, respectively; a saturation level of 52 kJ/m/sup 2/ was obtained for both the MHT wrought product and weld metal. Electron fractographic examination revealed that irradiation damage induced a transition from microvoid coalescence to channel fracture, which was associated with localized separation along planar slip bands. The effects of microstructure and operative fracture mechanisms were related to the fracture resistance of unirradiated and irradiated materials.
- Research Organization:
- Hanford Engineering Development Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76FF02170
- OSTI ID:
- 7054568
- Report Number(s):
- HEDL-SA-3527-FP; CONF-870480-1; ON: DE87004345
- Country of Publication:
- United States
- Language:
- English
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