Fracture-toughness variations in Alloy 718
The effect of product-form variations within a single heat on the J{sub Ic} fracture toughness behavior of Alloy 718 was examined at 24, 427 and 538{degree}C using the multiple-specimen J{sub R}-curve method. Three product forms (plate, round bar and upset forging) were tested in both the conventional and modified heat-treatment (CHT and MHT) conditions. In CHT material, the fracture toughness response was different for the three product forms -- plate having the highest toughness, bar the lowest. The MHT was found to improve the overall fracture resistance for each product form. In this condition, plate and forging had very similar toughness values, but J{sub Ic} levels for the bar were considerably lower. These results and WHC data previously reported for four other Alloy 718 heats were unalloyed statistically to establish minimum-expected J{sub Ic} values based on tolerance limits bracketing 90% of a total population at a 95% confidence level. Metallographic and fractographic examinations of the seven material lots were performed to relate key microstructural features and operative fracture mechanisms to macroscopic properties. Generally, coarse {delta} precipitates controlled fracture properties in CHT material by initiating secondary dimples that pre-empted growth of the primary dimples nucleated by broken carbide inclusions. The MHT dissolved the coarse {delta} particles and thereby suppressed secondary microvoid coalescence. This generally enhanced the fracture resistance of Alloy 718, except when alternate secondary fracture mechanism, such as channel fracture and dimple rupture at {delta}-phase remnants, prematurely interrupted primary microvoid growth. 25 refs., 12 figs., 12 tabs.
- Research Organization:
- Hanford Engineering Development Lab., Richland, WA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC06-76FF02170
- OSTI ID:
- 5693273
- Report Number(s):
- HEDL-TME-82-48; ON: DE91015630
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effects of irradiation on the fracture toughness of Alloy 718 plate and weld
Effect of heat treatment on the elevated temperature tensile and fracture toughness response of alloy 718. [427/sup 0/C and 538/sup 0/C]
Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
INCONEL 718
FRACTURE PROPERTIES
FORGING
FRACTOGRAPHY
FRACTURE MECHANICS
HEAT TREATMENTS
HIGH TEMPERATURE
LMFBR TYPE REACTORS
MEDIUM TEMPERATURE
MICROSTRUCTURE
PLATES
REACTOR MATERIALS
TOLERANCE
ALLOY-NI53CR19FE19NB5MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
BREEDER REACTORS
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
EPITHERMAL REACTORS
FABRICATION
FAST REACTORS
FBR TYPE REACTORS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCONEL ALLOYS
IRON ALLOYS
LIQUID METAL COOLED REACTORS
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
MECHANICS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM A
REACTORS
360103* - Metals & Alloys- Mechanical Properties
210500 - Power Reactors
Breeding