Precipitation kinetics of an aluminium alloy during Newtonian cooling simulated in a differential scanning calorimeter

The purpose of this report is to compare linear and non-linear cooling with respect to the precipitation behaviour of aluminium alloy EN AW-6082. Therefore an approximation of gas cooling by Newtonian law was performed. However, DSCs are typically designed for linear scanning. Hence a completely new method has been developed, to perform DSC-experiments during non-linear cooling. The temperature/time profile for two different types of DSCs was optimized avoiding overshoots at each change of cooling rate. Smooth curves were obtained by normalizing the measured heat flow rate by the actual heating rate yielding excess heat capacity as function of temperature. For the investigated aluminium alloy EN AW-6082 both kinds of cooling, linear and Newtonian, delivered comparable information about the characteristic precipitation reactions. Essential parts of the continuous cooling precipitation diagram could be recorded for both types of cooling. The intensities of the reactions, measured by the specific precipitation heat, were similar. (C) 2011 Elsevier B.V. All rights reserved.