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A comparative study of precipitate composition and volume fraction in an Al–Zn–Mg alloy using tomographic atom probe and small-angle X-ray scattering

2001; Taylor & Francis; Volume: 81; Issue: 10 Linguagem: Inglês

10.1080/01418610108217154

0141-8610

A. Deschamps, A. Bigot, F. Livet, Peter Auger, Y. Bréchet, D. Blavette,

Microstructure and mechanical properties

Abstract The composition and volume fraction of precipitates in an Al–Zn–Mg alloy are investigated by tomographic atom probe (TAP), small-angle X-ray scattering (SAXS) and transmission electron microscopy. Three states of ageing are characterized in detail: slightly underaged, containing mostly the metastable η′ phase; slightly overaged, containing η′ and the stable η phase; overaged, containing only η. The different methods are in full agreement about the last state, with a composition of η close to the bulk composition MgZn2, and a volume fraction of 4.5%. The TAP and SAXS results obtained for microstructures with smaller precipitates show some discrepancy. Notably, the TAP predicts a higher aluminium concentration in the precipitates as well as a higher volume fraction. The artefacts of the two techniques are reviewed in detail and a critical analysis of the results is carried out.