Microstructure and mechanical properties of rapidly solidified Al–7wt.%Mg–X (X=Cr, Zr or Mn) alloys

Abstract

In this study, the effect of the transition elements on the microstructure and mechanical properties of rapidly solidified Al–Mg–X alloys was investigated. As a result of the rapid solidification processing, fine equiaxed grains with a mean diameter of 2 μm were observed in these alloys. Many fine particles were found to be distributed rather homogeneously throughout the matrix with relatively big particles occasionally observed at grain boundaries. The ultimate tensile strengths of Al–Mg–X alloys were found to decrease rather remarkably at 150°C although the ductility was not increased, which may result from segregation of β(Al₃Mg₂) precipitates. Fine dimples were observed on the fracture surfaces for all alloy systems and the variation of the size and shape of dimples was not observed. The ductility at 530°C was found to be ∼100%, suggesting that grain boundary sliding did not contribute despite fine grain size stabilization. The absence of superplastic behavior may be associated with low boundary misorientation in rapidly solidified Al–Mg–X alloys.