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Título:
Macroestructuras de Aleaciones Al-Zn Obtenidas por Solidificación Direccional
Autor/es:
ALICIA ESTHER ARES ; RUBENS CARAM; CARLOS ENRIQUE SCHVEZOV
Lugar:
Joinville. Brasil
Reunión:
Congreso; SULMAT 2004. CONGRESSO DE CIENCIA DE MATERIAIS DO MERCOSUL; 2004
Institución organizadora:
Programa de pos-graduación en Ciencia y Ingeniería de los Materiales de la Universidade do Estado de Santa Catarina. Brasil
Resumen:
The columnar-to-equiaxed transition was investigated in Al 2 pct Zn and Al 4 pct Zn alloys solidified directionally from the chill face. Was considered the effect of thermal conditions during solidification, the cooling rates, interface velocities, local solidification time and the alloy composition. In directionally solidified alloys, the position at the CET occurs, and it depends on the temperature distribution in the system. It happens when the temperature gradients in the melt ahead of liquid interface become minimum and critical. This value of critical gradient seems to be independent of the solute concentration, natural convection, superheat, geometry of the mould and number of columnar and equiaxial grains. The interface velocities were compared with those calculated by Lipton equation and utilized in the WangBeckermann model for dendritic equiaxial growth. Transition occurs when the temperature gradients in the melt ahead of the columnar dendrites are in the range of (-1.54 to 0.91) °C/cm for Al 2 pct Zn, (-11.38 to 0.22) °C/cm for Al 4 pct Zn. At the time of the transition the liquidus interface velocities were about (0.11 to 0.70) cm/s and (0.11 to 0.18) cm/s, respectively. Also, a supercooling of (0.95 to 1.40) °C was measured, which was associated with the supercooling required for the nucleation and growth of the equiaxed grains ahead of the columnar front.