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Metallurgical and Materials Transactions A

, Volume 40, Issue 2, pp 365–376 | Cite as

Experimental and Analytical Investigations on Plane Strain Toughness for 7085 Aluminum Alloy

  • R.T. Shuey
  • F. BarlatEmail author
  • M.E. Karabin
  • D.J. Chakrabarti
Article

Abstract

Data are presented on plane strain fracture toughness, yield strength, and strain hardening for three orientations of samples from quarter-thickness (t/4) and midthickness (t/2) locations of alloy 7085 plates with different gages aged past peak strength with different 2nd step aging times (T7X). These data are fit to an expression adapted from Hahn and Rosenfield (1968), in which toughness is proportional to strain hardening, the square root of yield strength, and the square root of a critical strain ε c . Strain-hardening exponent n is replaced by an alternative measure, since the stress-strain data do not follow a power law. With increased overaging, the increase of strain hardening dominates the decrease of strength, such that toughness increases. The critical strain, which represents the influence of the microstructure on toughness, has no trend with overaging time. Constituents and grain boundary precipitates, thought to be the microstructural elements most differentiating alloy 7085 from alloy 7050, are quantified at t/4 and at t/2 on one plate. From this the greater critical strain at t/2 than at t/4 is mainly attributed to greater effective spacing of constituents. Critical strain is also greater with longitudinal loading and crack propagating in the long transverse direction, but definite understanding of this will require better anisotropic fracture mechanics and further microstructural characterization.

Keywords

Plastic Zone Critical Strain Linear Elastic Fracture Mechanic Uniform Elongation Plane Strain Fracture Toughness 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The authors gratefully acknowledge the contribution of their colleagues at Alcoa Technical Center: Messrs. J. Dalton and J. Brem for their assistance in mechanical testing, Mr. D.K. White for all the heat-treatment experiments, Mr. Paul Schwartz for SEM characterization, Dr. T.N. Rouns for the image analysis of grain boundary precipitates, and Dr. J. Boselli for reviewing the manuscript. Moreover, the authors thank Dr. M. Tiryakioglu (Robert Morris University) for his help in analyzing literature on microstructural models of toughness.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2008

Authors and Affiliations

  • R.T. Shuey
    • 1
  • F. Barlat
    • 1
    • 2
    Email author
  • M.E. Karabin
    • 1
  • D.J. Chakrabarti
    • 1
    • 3
  1. 1.Alloy Technology and Materials Research DivisionAlcoa Technical CenterPittsburghUSA
  2. 2.Materials Mechanics Laboratory, Graduate Institute of Ferrous Technology (GIFT)Pohang University of Science and Technology (POSTECH)PohangRepublic of Korea
  3. 3.WoodsideUSA

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