Afify N, Gaber A-F, Mostafa M, Anooz S B, 2002, "Phase transformation kinetics during the heating of an Al - 8 at% Li alloy" High Temperatures - High Pressures 34(5) 535 – 548
Phase transformation kinetics during the heating of an Al - 8 at% Li alloy
Nasser Afify, Abdel-Fattah Gaber, Mostafa Mostafa, Saud Bin Anooz
Abstract. The kinetics of the reactions (dissolution and precipitation) in Al - 8 at% Li alloy were investigated by differential scanning calorimetry (DSC). Analysis of nonisothermal DSC scans at different heating rates was carried out to evaluate the overall activation energies associated with the transformation processes during continuous heating of the quenched alloys. An average activation energy associated with dissolution of Guinier - Preston zones was found to be 73.42 ± 5.41 kJ mol-1, which implies that the dissolution process is controlled by the migration of lithium atoms through the aluminium matrix. The average activation energy of δ' phase precipitation was 62.65 ± 4.43 kJ mol-1. The activation energies of dissolution of the δ' phase and dissolution of the δ phase or lithium in the matrix were 132.47 ± 4.03 and 398.40 ± 3.98 kJ mol-1, respectively. The reaction order of all processes indicates that they occur three-dimensionally throughout the aluminium matrix. δ and δ' phases have been detected in naturally (1800 min) aged specimens by x-ray diffraction.
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