SEDL / STP / STP496-EB / STP26927S

Plane Strain Fracture Toughness of Aluminum Alloys at Room and Subzero Temperatures

Nelson, FG
Research engineer and chief, Alcoa Research Laboratories, New Kensington, Pa.

Kaufman, JG
Research engineer and chief, Alcoa Research Laboratories, New Kensington, Pa.

Pages: 13    Published: Jan 1971

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Abstract

Plane strain fracture toughness tests have been made at room temperature, -112, and -320 F on plates of six aluminum alloys and tempers: 2014-T651, 2024-T851, 6061-T651, 7075-T651, 7075-T7351, and 7079-T651. The data indicate that the plane strain fracture toughness, K^Ic, of each of the alloys at the subzero temperatures is as high as or higher than that at room temperature. At -320 F apparently valid values of K^Ic ranged from 4 (7075-T7351) to 23 percent (2014-T651 and 7075-T651 ) higher than at room temperature. An even larger difference was indicated for 6061-T651 (about 40 percent higher), but the specimens tested at -320 F were not thick enough to satisfy the requirements of ASTM Test E 399 - 70 T. For the alloys of most interest for cryogenic applications, 2014-T651 and 6061-T651, the critical crack sizes at cryogenic temperatures are indicated to be as large as or larger than those at room temperature when evaluated at either a fixed operating stress or a constant percentage of the yield strength.