COLUMNAR TO EQUIAXED TRANSITION STUDIES IN ALUMINUM-MAGNESIUM AND ALUMINUM-ZINC ALLOYS

ARES, ALICIA;; RIOS, CARLOS;; CARAM, RUBENS; SCHVEZOV, CARLOS

Light Metals 2003

Paul E. Crepeau, editor. A publication of the Minerals, Metals, & Materials Society

Lugar: San Diego, California. USA.; Año: 2003; p. 1047 - 1054

The columnar-to-equiaxed transition (CET) was investigated in Al-2wt%Mg, Al-4wt%Mg, Al-2wt%Zn and Al-4wt%Zn alloys directionally solidified from the chill face. The transition occurs when the temperature gradients in the melt ahead of the columnar dendrites are in the range of (-1.54 to 0.31) °C/cm for Al-2wt%Mg, (-1.67 to 0.09) °C/cm for Al-4wt%Mg, (-1.54 to 0.91) °C/cm for Al-2wt%Zn and (-11.38 to –0.22) °C/cm for Al-4wt%Zn. When the CET occurs, the liquidus interface velocities were about (0.10 to 0.14) cm/s, (0.11 to 0.18) cm/s, (0.10 to 0.14) cm/s and (0.12 to 0.18) cm/s, respectively. Also, a supercooling of (0.23 to 1.15) °C for Al-Mg and (0.91 to 1.40) °C for Al-Zn where measured, which was associated with the supercooling for the nucleation and growth of the equiaxed grains ahead of the columnar front. The results obtained in both alloys systems are presented and discussed.