⁴⁵Sc nuclear magnetic resonance analysis of precipitation in dilute Al-Sc alloys

Kinetics and mechanisms of precipitation in an Al–0.2wt.% Sc alloy

“…11. For temperatures of 370 • C and above the present solvus estimates increase with increasing temperature, and the data points are within the spread of previously reported values [19,26,33,34,[44][45][46][47][48][49]. It thus seems that the current estimates are good in this temperature regime.…”

“…In order to minimise the Sc-addition that is needed to give the desired effects in an alloy, it is necessary to be able to predict the modus and kinetics of the formation of Al 3 Sc particles from a supersaturated solid solution. Several investigations of the precipitation kinetics and precipitation mechanisms of Al 3 Sc have been published in the technical literature over the past 10-20 years [16][17][18][19][20][22][23][24][25][26][27][28][29][30][31][32][33]. The published material does, however, give only a limited overview of the regimes in which either of the two precipitation mechanisms occur, and the differences in precipitation kinetics between the two mechanisms are not accounted for.…”

In situ evaluation of the microstructure evolution during rapid hardening of an Al–2.5Cu–1.5Mg (wt.%) alloy

“…NMR distinguishes atoms on the basis of their nuclear magnetic moment, which depends on the local atomic environment and has recently been used to probe precipitation processes in Al alloys [39][40][41][42]13,43]. The spectroscopy is done in a high applied magnetic field, and the resonance frequency is proportional to the magnetic field experienced at the nucleus in the compound under study.…”

The Role of Excess Vacancies on Precipitation Kinetics in an Al-Mg-Sc Alloy

“…Second, the NMR spectra show no evidence of other Sc containing phases, confirming the expected result that the Al 3 Sc forms directly without intermediate precipitates. It should be noted that compared to binary Al-Sc alloys, [18] the Al 3 Sc peaks observed here on aging at 350°C exhibited extensive and symmetric wings due either to imperfectly formed Al 3 Sc crystallites or to Mg proximity. Finally, it is worth noting that the precipitation start and finish times estimated from resistivity are consistent with the observed appearance of the Al 3 Sc peak in the NMR spectra and the relatively small change in this peak for measurements between 1 and 2 hours.…”