Coincidence Doppler broadening study of phase decomposition in a continuous cast AA 2037 Al alloy

Phase decomposition in hot band of a continuous cast AA 2037 Al alloy was investigated by coincidence Doppler broadening (CDB) of positron annihilation radiation and positron annihilation lifetime spectroscopy (PALS). It was found that there existed V-Cu and V-Cu-Mg complexes in the as-received hot band at room temperature. At 200°C, positron average lifetime appeared to be a maximum value because of the formation of semi-coherent precipitates. The shape of the CDB ratio curve was found to be characteristic of Mn, which indicated the formation of V-Mn complexes or the existence of Mn clusters in the semicoherent precipitates. Above 250°C, coarsening and dissolution of semi-coherent precipitates resulted in a decrease in lifetime and disappearance of the Mn signal, but the Cu signal increased clearly with increase in annealing temperature.