β′ and β precipitation in an Al–Mg alloy studied by DSC and TEM
Starink, M.J. and Zahra, A.-M. (1998) β′ and β precipitation in an Al–Mg alloy studied by DSC and TEM. Acta Materialia, 46, (10), 3381-3397. (doi:10.1016/S1359-6454(98)00053-6).
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Precipitation in Al–16 at.%Mg is investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The shape of the β′ formation DSC effect is interpreted with a novel theory and the curves obtained on the basis of this new theory fit well to the experimental curves. The s parameter derived from these fits, which is akin to the Avrami parameter n appearing in the Johnson–Mehl–Avrami–Kolmogorov model, is larger than 2.5, indicating that β′ precipitation is an autocatalytic process. TEM showed the abundant presence of defects (mostly dislocation loops) but no evidence of nucleation of β′ precipitates on these defects. The enthalpies of formation of the β and β′ phases are derived as 15.7 and 11.5 kJ per mol Mg, respectively.
|Keywords:||aluminium alloys, precipitation (chemical), differential scanning calorimetry, transmission electron microscopy, Al-Mg, dislocations (crystals), nucleation, curve fitting, mathematical models, enthalpy, John-Mehl-Avrami-Kolmogorov model|
|Subjects:||T Technology > TN Mining engineering. Metallurgy
Q Science > QD Chemistry
Q Science > QA Mathematics
|Divisions:||University Structure - Pre August 2011 > School of Engineering Sciences
|Date Deposited:||12 Oct 2006|
|Last Modified:||02 Mar 2012 11:48|
|Contributors:||Starink, M.J. (Author)
Zahra, A.-M. (Author)
|Contact Email Address:||M.J.Starink@soton.ac.uk|
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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