ISSN:
1662-9752
Quelle:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Thema:
Maschinenbau
Notizen:
A numerical model based on the Kampmann and Wagner method wasdeveloped to predict the evolution of precipitate distribution in 7xxx aluminium alloyduring non-isothermal heat treatments. The model considers the nucleation, growthand coarsening/dissolution of the metastable and equilibrium precipitate phases, η'and η with their stochiometric composition, MgZn2. Constitutive model equations fornucleation were based on the classical theory of nucleation whilst growth andcoarsening were treated using classical phase transformation theory. The transitionbetween η' and η, where η' acts as a precursor for η was also accounted for in themodel. Differential scanning calorimetry was used to calibrate the homogeneousprecipitation kinetics. The model also predicts the evolution of grain boundaryprecipitates and their effect on precipitate free zone size. Jominy end quench testswere performed to calibrate grain boundary precipitation kinetics. Precipitation ondislocations and dispersoids was considered. The dislocation and dispersoid densitieswere varied to represent different regions of a grain and therefore account for thespatial distribution of preferential heterogeneous precipitation sites. Comparisonbetween the model prediction and experimental characterisation of the microstructureevolution of a friction stir welded 7449 aluminium alloy was found to be reasonablyconsistent
Materialart:
Digitale Medien
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.519-521.1435.pdf
