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Lecture

Simulation of precipitation in 6xxx aluminium alloys during continuous cooling DSC

Wednesday (06.11.2019)
14:35 - 14:55
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Precipitation during continuous cooling from an annealing temperature occurs only for slow and intermediate cooling rates. This behavior of Al-Mg-Si based 6xxx alloys is relevant in technological processing such as extrusion or forging, which calls for the realization of predictive simulation of precipitation kinetics.

The main aspect of this work lies on thermokinetic simulation of differential scanning calorimetry (DSC) cooling curves based on thermodynamic phase descriptions of Al-base systems implemented in the software package MatCalc. For the validation of simulation trends, precipitation states produced by quenching experiments from different temperatures during continuous cooling are analyzed by scanning and transmission electron microscopy. Precipitation of the thermodynamically stable Mg2Si phase occurring at higher temperatures, followed by metastable B’/β’-phases towards lower temperatures, is observed. Microstructural investigations show precipitates at grain boundaries, in the grain interior and attached to dispersoids. DSC measurements for different cooling rates confirm temperatures of two distinct precipitation events during continuous cooling.

The identified precipitation trends are in accordance with previous findings [1] and represent a suitable dataset for the validation of the thermokinetic simulation. Refining the thermodynamic description of the B´ phase [2] delivers good agreement of predicted nucleation start temperatures and precipitate sizes.


[1] B. Milkereit, M.J. Starink, Quench sensitivity of Al–Mg–Si alloys: A model for linear cooling and strengthening, Materials & Design 76 (2015) 117-129.

[2] E. Povoden-Karadeniz, P. Lang, P. Warczok, A. Falahati, W. Jun, E. Kozeschnik, CALPHAD modeling of metastable phases in the Al–Mg–Si system, Calphad 43 (2013) 94-104.






 

Speaker:
Additional Authors:
  • Andreas Pasching
    Neuman Aluminium , Werkstrasse 1, Marktl im Traisental
  • Prof. Dr. Ernst Kozeschnik
    Institute of Materials Science and Technology, TU Wien, Getreidemarkt 9
  • Prof. Dr. Erwin Povoden-Karadeniz
    Christian Doppler Laboratory for Interfaces and Precipitation Engineering CDL-IPE & Institute of Materials Science and Technology , TU Wien, Getreidemarkt 9