Investigation of early stages of precipitation in Al-Mg-Si alloys

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The group of Al-Mg-Si alloys (6000 alloys) is investigated. The aim is to understand the precipitation processes at room temperature (and also at other temperatures in the range -20 to 70°C) immediately after solutionising and quenching and to relate the findings to the ensuing artificial ageing behaviour. We apply a multi-method concept in which the kinetics of precipitation are monitored by in-situ measurements of positron lifetime and electrical resistivity and by fast ex-situ measurements of hardness and heat dissipation. The already known stages of early precipitation are to be established for a range of binary, ternary and even more complex alloys. The temperature dependence of the transition times between various stages and complete modelling of resistivity curves yield activation energies for the various stages. The potential of fast dynamic positron lifetime measurement is used to obtain information about the mechanisms of early atom cluster formation.