Environment-assisted fatigue-crack growth behavior of structural aluminum alloys. [Ingot processed 7050-T7451, 7050-T651, 7075-T651 and powder processed 7091-T7E69]

Conference · · TMS (The Metallurgical Society) Paper Selection; (USA)

OSTI ID:5366772

Pao, P S; Wei, R P ^[1]

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1. McDonnell Douglas Research Laboratories, St. Louis, MO (USA)

The influence of water vapor on the fatigue-crack growth kinetics in P/M and I/M aluminum alloys has been studied by comparing the crack growth response of I/M-processed 7050-T7451, 7050-T651, and 7075-T651 to P/M-processes 7091-T7E69. Water vapor causes a 200-300% increase in fatigue crack growth rate in all aluminum alloys. Fatigue-crack growth rates are about 80% higher and the saturation vapor pressure is an order-of-magnitude lower in P/M alloys than I/M alloys. The observed higher fatigue crack growth rate in P/M alloys can be attributed to their finer grain/subgrain microstructures. The lower saturation vapor pressure in P/M alloys is associated with smooth macroscopic fracture surface morphology which facilitates water vapor transport to the crack-tip region. The environment-assisted fatigue-crack growth model is discussed in relation to alloy strength, microstructure, and heat treatment.

• OSTI ID: 5366772
• Report Number(s): CONF-840909-; CODEN: TMPSA
• Journal Information: TMS (The Metallurgical Society) Paper Selection; (USA), Vol. 56; Conference: TMS-AIME fall meeting, Detroit, MI (USA), 16-20 Sep 1984; ISSN 0197-1689
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
CRACK PROPAGATION
WATER VAPOR
CATALYTIC EFFECTS
COMPARATIVE EVALUATIONS
CRACKS
FATIGUE
FRACTURE MECHANICS
HEAT TREATMENTS
KINETICS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
METALLURGY
MICROSTRUCTURE
POWDER METALLURGY
SURFACE PROPERTIES
ALLOYS
ALUMINIUM ALLOYS
CRYSTAL STRUCTURE
FLUIDS
GASES
MECHANICS
VAPORS
360103* - Metals & Alloys- Mechanical Properties