The microstructures of as spun and as annealed ribbons in rapidly solidified Al 5Zn 2.5Mg 2.5Mn (mass,%)
alloy were investigated by using differential scanning calorimetry(DSC),X ray diffraction (XRD),transmission electron microscopy(TEM) and energy dispersive spectroscopy (EDS). The
hardness of the alloy was also measured by means of Vickers hardness meter.The results showed that there were four exothermic peaks in the DSC curve occurring in the temperature range of 90 to 110℃ and 260 to 280℃ corresponding to
precipitation of the η (MgZn\-2) and T (Al\-2Mg\-3Zn\-3)
phase respectively,similarly,the exothermic reaction at 460℃ and 480℃ was related to the formation of Al\-3Mn and Al\-6Mn dispersoid,which is consistent with the results of XRD and TEM analysis. The
microstructure of the as spun alloy was in supersaturated solid solution state and no second phase in Al matrix. When annealing at 300℃ for 1 hour,there were η and T phase in the
matrix and no Al Mn phase.Heat treatment at 500℃ for 1 hour lead to the formation of Al\-3Mn and Al\-6Mn
dispersoid and the dissolution of η and T phase.Evolution of microstructure of the alloy was checked and verified by the change of the lattice constant of the Al matrix and the hardness of the alloy. Significant increase in hardness was attributed to the precipitation or transformation of the Al Mn phase.
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