Quantitative evaluation of precipitates in an Al–Zn–Mg–Cu alloy after isothermal aging

• Published in: Materials characterization Vol. 56; no. 2; pp. 121 - 128
• Main Authors: Du, Z.W., Sun, Z.M., Shao, B.L., Zhou, T.T., Chen, C.Q.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.03.2006; Elsevier Science
• Subjects: ALUMINIUM ALLOYS; Al–Zn–Mg–Cu Alloys; COPPER ALLOYS; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; HARDENING; MAGNESIUM ALLOYS; MATERIALS SCIENCE; MICROSTRUCTURE; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitate size; Precipitate volume fraction; SMALL ANGLE SCATTERING; Small angle X-ray scattering; Solidification; SYNCHROTRON RADIATION; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; ZINC ALLOYS; Precipitate size; Al–Zn–Mg–Cu Alloys; Precipitate volume fraction; Small angle X-ray scattering; Precipitation; Volume fraction; Copper alloys; Aging; Precipitates; Al-Zn-Mg-Cu Alloys
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2005.10.004

The evolution of microstructure parameters (precipitate size and volume fraction) for an Al–8.0 Zn–2.05 Mg–1.76 Cu alloy during isothermal ageing has been studied by synchrotron-radiation small angle X-ray scattering (SAXS) combining transmission electron microscopy (TEM). The results show that the precipitates are only a few nanometers even at higher temperature 160 °C up to 72 h (5.82 nm). The precipitate volume fraction reaches a plateau except ageing at 120 °C and the maximum is about 0.052–0.054 in the range 140–160 °C. Models describing the evolution of these two parameters with ageing temperature and time have been constructed for our further predicting the precipitate hardening. The coarsening of precipitate is consistent with LSW (Lifshitz–Slyozov–Wagner) model even in the initial stage where volume fraction is still varying. The activation energy of coarsening regime has been determined to be about 1.25 ± 0.02 eV.