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 investig ated. As a result of the rapid solidification processing, fine equiaxed gra ins 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 boundar ies. The ultimate tensile strengths of Al-Mg-X alloys were found to decreas e rather remarkably at 150 degreesC although the ductility was not increase d, which may result from segregation of beta (Al3Mg2) precipitates. Fine di mples 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 boun dary sliding did not contribute despite fine grain size stabilization. The absence of superplastic behavior may be associated with low boundary misori entation in rapidly solidified AI-Mg-X alloys. (C) 2001 Elsevier Science B. V. All rights reserved.