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

Abstract

AbstractPhase 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 semi‐coherent 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. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)