Calorimetric studies of 2024 Al-Cu-Mg and 2014 Al-Cu-Mg-Si alloys of various tempers

摘要

Differential scanning calorimetry (DSC) technique is used to study the solid reactions in the 2024 Al-Cu-Mg and 2014 Al- Cu-Mg-Si alloys of solutionised-water quenched, naturally aged, artificially under-, peak-, over-aged states at four different heating rates (v(h)) of 5 degrees C min(-1) , 10 degrees C min(-1) , 15 degrees C min(-1) and 20 degrees C min(-1) . All the exothermic and endothermic peaks in the DSC curves have been identified and discussed. The noticeable differences observed in the DSC curves of the 2024 and 2014 alloys have been explained which are attributed to the variations of the Cu, Mg and Si solute contents. DSC curves showed at different heating rates that all the peaks (except a few) have shifted to higher temperature with increasing heating rates (v(h)). The peak temperatures (T-p) and the heat evolved and absorbed (Delta H) during the precipitation and dissolution reactions have been determined with the help of in-built software available with the DSC unit. Attempts have been made to explain the solid-state reactions sequences in these alloys with the help of XRD and TEM micrographs.