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H.P. Degischer, A. Falahati, G. Requena, H. Mohammadian:
"Precipitation Kinetics in Al-Alloys Revealed by Dilatometry";
Talk: Materials Science and Engineering - MSE 2008, Nürnberg; 09-01-2008 - 09-04-2008.

Scanning and isothermal dilatometry are applied to investigate the precipitation kinetics in Al-alloys containing Si, Ge, Mg, Cu. The sequence, kinetics and amount of Si or Ge precipitation are compared with results of differential scanning calorimetry (DSC) and isothermal micro-calorimetry (µIC). Selected states of precipitates are verified by transmission electron microscopy (TEM).
The relative increase or reduction in length are measured by dilatometry during thermal exposure of binary and ternary Al-alloy samples. The derived temperature dependence of the instantaneous coefficient of thermal expansion is correlated with significant volume changes during precipitation or dissolution of the elements Si and Ge. Isothermal dilatometry yields a quantitative measure of the precipitation rate and of the temperature dependent volume fraction of precipitated Si or Ge. The influence of the alloying elements Mg and Cu is presented as well as that of the solution treatment temperature and of the cooling rates thereafter. The presence of eutectics and their degree of spheroidisation affect the precipitation kinetics of Si and Ge as well. Dilatometry can serve as a method to investigate the growth of Si and Ge precipitates in binary and as well as in complex age-hardening alloys.