Fracture Toughness Variations in Alloy 718

[+] Author and Article Information
W. J. Mills, L. D. Blackburn

Hanford Engineering Development Laboratory, Westinghouse Hanford Company, Westinghouse Electric Corporation, Richland, Wash. 99352

J. Eng. Mater. Technol 110(3), 286-293 (Jul 01, 1988) (8 pages) doi:10.1115/1.3226050 History: Received August 10, 1987; Online September 15, 2009


Heat-to-heat and product-form variations in the JIc fracture toughness of Alloy 718 were examined at 24°C, 427°C, and 538°C using the multiple-specimen JR -curve method. Five different material heats along with three product forms from one of the heats were tested in the conventional heat-treatment condition. Statistical analysis revealed only two significantly different JIc levels of 48 kJ/m2 and 74 kJ/m2 for these materials. These two mean JIc levels were independent of temperature. A minimum-expected JIc level based on a tolerance interval bracketing 90 percent of the lower JIc population at a 95 percent confidence level was evaluated as 33 kJ/m2 . Coarse δ precipitates controlled the fracture properties by initiating secondary dimples that pre-empted continued growth of primary dimples nucleated by broken carbide inclusions.

Copyright © 1988 by ASME
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