Computational phase studies in commercial aluminium and magnesium alloys

Computational phase studies in commercial aluminium and magnesium systems a re presented using the example of the quaternary Al-Cu-Mg-Zn system. Thermo dynamic datasets for the ternary subsystems have been developed, and modell ing of the ternary solution phases C14, C15, and C36 (Laves phases) and the so called T and V phases is described. For the descriptions of these phase s the crystal structures, thermodynamic data, and phase equilibrium data we re taken into account. The ternary datasets were combined in a single compu ter database. Some of the ternary solution phases also show large homogenei ty ranges extending into the quaternary system, ranging from one boundary t ernary system to the other. This behaviour was taken into account to establ ish a quaternary thermodynamic dataset, The results are illustrated by mean s of calculated ternary and quaternary isothermal sections, vertical sectio ns, and phase fraction diagrams. To illustrate the computer simulation of m icrostructural development in aluminium and magnesium light alloys during r apid solidification processes, a Scheil-Gulliver calculation for the magnes ium casting alloy AZ91 is presented. MST/4803.