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Toughness-strength relations in the overaged 7449 Al-Based alloy

By N. Kamp, I. Sinclair and M.J. Starink


This article examines the relationship between plane strain fracture toughness, KIc, the tensile properties, and the microstructure of the overaged 7449 aluminum-plate alloy, and compares them to the 7150 alloy. The 7449 alloy has a higher content of ??/? precipitates; and, the 7150 alloy contains a greater amount of coarse intermetallic particles, as it contains an appreciable amount of coarse S phase (Al2CuMg), which is largely absent in the 7449 alloy. The toughness of the alloys shows an increase on overaging, and the 7449 alloy shows a reasonably linear toughness—yield strength relation on extended overaging. Several mechanisms of failure occur: coarse voiding at intermetallics and a combined intergranular/transgranular shear fracture mode, with the former becoming more important as overaging progresses. Drawbacks of existing models for toughness are discussed, and a new model for plane strain fracture toughness, based on the microstructurally dependent work-hardening factor, KA, introduced in Ashby's theory of work hardening, is developed. This model predicts a linear relation between KIc and K0.85A/?0.35ys, where ?ys is the yield strength, which is consistent with the experimental data

Topics: TJ, TL
Year: 2002
OAI identifier:
Provided by: e-Prints Soton

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