MECHANISMS OFPRECIPITATES FORMATION IN AN Al- Cu- Li-ZrALLOYUSINGDSC TECHNIQUE AND ELECTRICALRESISTANCE MEASUREMENTS

Abstract: guinier-preston (gp) zone formation and precipitation behavior of t1 (al2culi) phase during the ageingof an al-cu-li-zr alloy was studied by differential scanning calorimetry (dsc) technique and electrical resistancemeasurement of the samples. results show that endothermic effects in the thermograms of the alloy between 180°cand 240°c can be related to the enthalpy of gpzones dissolution. formation of gpzones in the structure increasedhardness, tensile strength and electrical resistance of the al-cu-li-zr alloy. furthermore, precipitation of t1 phaseoccurred in temperature range of 250ºc to 300ºc whereas its dissolution occurred within the temperature of 450-530ºc. activation energies for precipitation and dissolution of t1 phase which were determined for the first time inthis research, were 122.1(kj/mol) and 130.3(kj/mol) respectively. results of electrical resistance measurementsshowed that an increase in the aging time resulted in the reduction of electrical resistance of the aged samples.