[delta][prime]-Phase precipitation at low temperature in a duplex-aged 8090 Al-Li alloy

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Materials Characterization; (United States)

DOI:https://doi.org/10.1016/1044-5803(94)90053-1· OSTI ID:7021645

Watkinson, P C; Martin, J W ^[1]

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1. Univ. of Oxford (United Kingdom). Dept. of Materials

It is known that duplex aging of 8090 increases the toughness of peak-aged material. A decrease in toughness has been reported after 1 month's further aging at low temperatures (e.g., 80 C), thus losing the effects of the second aging step. In the present work, samples of duplex aged 8090 have been aged at 80 C for periods in excess of 5 months, and changes in hardness have been correlated with microstructural changes observed by transmission electron microscopy and differential scanning calorimetry. A marked change in the size distribution of the main hardening phase ([delta][prime]) occurs, with a previously unreported precipitation of very small [delta][prime] particles in both the grain interiors and (after several months) in the precipitate-free zones around the grain boundaries. This is accompanies by a drop in hardness, to a minimum after 1 months, followed to a rise to a maximum after 5[1/2] months. Mechanisms have been suggested for the observed changes in the properties of the alloy.

• OSTI ID: 7021645
• Journal Information: Materials Characterization; (United States), Vol. 33:1; ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
AGE HARDENING
MORPHOLOGICAL CHANGES
LITHIUM ALLOYS
COPPER ADDITIONS
EXPERIMENTAL DATA
FRACTURE PROPERTIES
MAGNESIUM ADDITIONS
MICROSTRUCTURE
PHASE STUDIES
ZIRCONIUM ADDITIONS
ALLOYS
ALUMINIUM ALLOYS
COPPER ALLOYS
DATA
HARDENING
INFORMATION
MAGNESIUM ALLOYS
MECHANICAL PROPERTIES
NUMERICAL DATA
ZIRCONIUM ALLOYS
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties