Precipitation behaviors in Al-Cu-Mg and 2024 aluminum alloys

Journal Article · Sun Sep 01 04:00:00 EDT 1996 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/BF02652342· OSTI ID:382501

Shih, H C; Ho, N J; Huang, J C ^[1]

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1. National Sun Yat-sen Univ., Kaohsiung (Taiwan, Province of China). Inst. of Materials Science and Engineering

The precipitation behaviors and aging reactions of the pseudobinary Al-Cu-Mg alloy and the commercial 2024 alloy under unstretched and stretched conditions have been investigated in this study by means of conductivity and hardness measurements, differential scanning calorimetry, and transmission electron microscopy (TEM). The morphologies and growth modes of various defects and transition phases as well as the interaction among them were widely discussed. In particular, an electron diffraction ring pattern was found to correspond to the axial growth of the GPB2 zone. This suggested that the atom groups constructing this cylindrical zone are statistically, uniformly arranged in the adjacent {l_brace}100{r_brace}{sub Al} planes and the GPB2 zone is only a partially ordered version of the GPB zone in <001>{sub Al} directions. Moreover, few GPB2 zones can survive long time overaging due to the Gibbs-Thomson effect. As for the S{prime} precipitates, they preferentially nucleate on dislocations. During subsequent growth, they can further coalesce into two morphologies (corrugated sheets and wide plates) for the unstretched specimens. Therefore, the rate of Ostward ripening decreases and the peak hardness becomes flattened. Finally, based on the present analyses, the aging sequence of the two alloys studied could be revised with respect to previous investigations and their isothermal aging reactions can be subdivided into five main stages. These stages correspond to (1) GPB zone precipitation, (2) fast in situ precipitation of GPB2 zones from GPB zones and their subsequent growth, (3) fast nucleation and accelerating growth of the S{prime} phase, (4) decelerating growth of the S{prime} phase, and (5) Ostward ripening of the S{prime} and S phases, respectively.

• Sponsoring Organization: USDOE
• OSTI ID: 382501
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 9 Vol. 27; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
36 MATERIALS SCIENCE
AGING
AIRCRAFT
ALUMINIUM BASE ALLOYS
CALORIMETRY
COPPER ALLOYS
DEFECTS
DISLOCATIONS
ELECTRIC CONDUCTIVITY
HARDNESS
MAGNESIUM ALLOYS
MATERIALS
MICROSTRUCTURE
MORPHOLOGY
NUCLEATION
SOLUTES
TRANSMISSION ELECTRON MICROSCOPY
VACANCIES