Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1621976 | Journal of Alloys and Compounds | 2009 | 5 Pages |
Thermal stability and structural changes during isothermal heat treatment of nanostructured Al2024 alloy prepared by mechanical milling (MM) were investigated. Al2024 powders were subjected to high-energy milling for various times to produce nanostructured alloy. Nanostructured Al2024 alloy was subsequently annealed at 150–550 °C for 1–3 h under argon atmosphere. The as-milled and annealed powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that after 30 h of milling, an Al–Cu–Mg supersaturated solid solution with a grain size of 30 nm was obtained. This structure was then isothermally heat-treated at various temperatures for different times. The CuAl2 and CuMgAl2 precipitates formed after heat treatment at T < 350 °C. In contrast to CuAl2 phase, CuMgAl2 precipitates disappeared on XRD traces taken after annealing at temperatures higher than 350 °C. Investigation of grain growth kinetics showed that nanostructured Al2024 had high thermal stability so that Al grain size remained in nanosized scale (about 70 nm) even after heating at 550 °C for 3 h. The value of grain growth exponent and activation energy at different annealing temperatures were obtained and discussed in terms of solute and second phase drag effects.