Rationalizing Al-Mg, Al-Mg-Si, and multicomponent aluminum alloy design with segregation susceptibility predictions

Macro-segregation is a type of unacceptable defects, which normally occurs for aluminum alloys and other nonferrous alloys. In this work, the macro-segregation susceptibility (MAS) of commercial 5xxx and 6xxx alloys and Al-Mg and Al-Mg-Si alloys have been investigated via a criterion based on the solidification curves from thermodynamic calculations. Equilibrium solute distribution coefficients, k, with different initial alloying concentrations and their relationships with the MAS are discussed. Of all commercial 5xxx and 6xxx aluminum alloys, the AA5754, AA5182, AA6181A and AA6016 alloys have shown less susceptible to macro-segregation than others. Of all Al-Mg and Al-Mg-Si alloys in this study, Al-Mg alloys with higher Mg, and Al-Mg-Si alloys with both higher Mg and Si have shown less susceptible to macro-segregation than other compositions. Finally, the role of mass transfer behavior in improving macro-segregation is discussed from the perspective of thermodynamic and kinetic calculations.