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

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 mum 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 degreesC although the ductility was not increased, which may result from segregation of beta (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 degreesC was found to be similar to 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 AI-Mg-X alloys. (C) 2001 Elsevier Science B.V. All rights reserved.