Recording of continuous cooling precipitation diagrams of aluminium alloys

The purpose of this report is to present a methodology to record continuous cooling precipitation (CCP) diagrams over the complete range of technical interesting cooling rates for some aluminium wrought alloys. With the information out of CCP-diagrams, the quenching step of the heat-treatment process “Age Hardening” can be optimized. The nanosized precipitations were detected via Differential Scanning Calorimetry (DSC) by identifying their exothermal heat. Aluminium wrought alloy EN AW-6005A was age hardened in three different DSCs whereby cooling rate range varies over 3 orders of magnitude. With increasing cooling rate, the precipitation heat is decreasing. The CCP-diagram covers cooling rates form close to equilibrium conditions at 0.1 K/min up to the critical cooling rate at 375 K/min where the precipitation reaction is suppressed completely. The DSC delivers a very useful method to record full range CCP-diagrams of aluminium alloys. Opposite to other possible methods, it also delivers a measure for the amount of the nanosized precipitates by the amount of released heat. A strategy is presented for the deconvolution of overlapping DSC-peaks.