A STUDY OF THE DECOMPOSITION OF ALPHA(AL)-SOLID SOLUTION ON HEATING FOR QUENCHING OF CAST MANGANESE-ALLOYED AL-10-PERCENT MG AND AL-6-PERCENT ZN-1.5-PERCENT MG-1-PERCENT CU CAST ALLOYS

Transmission electron microscopy was used to study the phase compositi on and the kinetics of phase transformations during the decomposition of alpha(Al)-solid solution on heating for quenching of cast Al-10% Mg -0.4% Mn and Al-6% Zn-1.5% Mg-1% Cu-0.4% Mn alloys. Complex electron d iffraction patterns of manganese aluminide particles were identified. Electron microscopy data were used to plot isothermal transformation d iagrams of the decomposition of alpha(Al)-solid solution on heating of cast alloys. The phase composition and precipitation kinetics of mang anese aluminides were found to depend on the composition, of the solid solution regarding the major alloying elements. Thermodynamic calcula tions were carried out to construct a polythermal section Al-10% Mg-Mn and determine the distribution of manganese across the section of a d endrite cell as a result of non-equilibrium solidification.