The Fracture of Wrought Metals
Final rept. 1 Jul 1972-31 Oct 1976
DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS ENGINEERING
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The mechanism of prestrain embrittlement in wrought metals was examined in three alloy systems Armco iron, 7075-T651 aluminum, and a copper- SiO2 alloy. Specimens were compressively prestrained, then tested in tension in and transverse to the direction of compression. Prestrain embrittlement was observed in all three alloys, depending on test conditions. In the copper-base alloy, which was in the form of thin sheet, the retained tensile ductility was reduced linearly by inplane compressive prestrain. Fracture was initiated by crystallographically-oriented voids generated at particle-matrix interfaces during compression. The behavior of Armco iron was similar in that particle- matrix void nucleation during compression provides fracture initiation sites that lead to brittle cleavage failure at room temperature during subsequent notch tensile testing. Prestrain had little influence on smooth bar tensile test results. Crystallographic texture development was shown to play a part in the embrittlement but tests under high pressure that suppressed void nucleation showed the role of texture to be secondary. Prestrain embrittlement in the aluminum alloy results from the interaction of intense shear bands, formed by sufficient compressive prestrain, with the grain boundaries to give a partially intergranular fracture.
- Metallurgy and Metallography
- Quantum Theory and Relativity