Experimental study and phase diagram calculation in Al-Zn-Mg-Si quaternary system

The phase equilibrium of the Al-Zn-Mg-Si quaternary system containing (Al), (Si), MgZn(2) and Mg(2)Si phases has been studied by means of scanning electron microscopy (SEM), electron dispersive spectrometry (EDS). X-ray diffraction (XRD) and differential scanning calorimeter (DSC) as well as calculation of phase diagram based on PANDAT software. Two three-phase fields and one four-phase field among the 15 wt% Al-Zn-Mg-6 wt% Si alloys in the concentration of Zn ranging from 57 wt% to 67 wt% have been confirmed at 573 K The result showed non-existence of quaternary compound in this region Based on the experimental results, the appropriate thermodynamic description of Mg-Si system was chosen The ternary interactions in the liquid phase of Al-Mg-Si and Mg-Zn-Si systems have been assessed and the calculated ternary phase diagrams agreed well with the experimental data Combining with the related ternary systems, the thermodynamic description of the Al-Zn-Mg-Si system was presented, and the good agreement between the calculated results and the experimental results was obtained. (C) 2010 Elsevier B V All rights reserved