Análisis of Solidification Parameters during Solidification of Lead and Aluminum Base Alloys

ALICIA E. ARES; SERGIO F. GUEIJMAN ,; RUBENS CARAM; CARLOS E. SCHVEZOV

JOURNAL OF CRYSTAL GROWTH

Elsevier Science B.V.

Lugar: Sara Burgerhartstraat 25. 1055 KV Amsterdam. Netherlands.; Año: 2005 vol. 275 p. 319 - 327

0022-0248

Experiments were carried out in which the conditions of columnar to equiaxed transition (CET) in directional solidification of dendritic alloys are known, in alloys sytems such as Pb-Sn, Al-Cu, Al-Si, Al-Mg and Al-Zn. These experiments allow determining that the transition does not occur in an abrupt form in the samples and it is presented when the gradient in the liquid ahead of the columnar dendrites reaches critical and minimum values, being negative in most of the cases. The transition occurs when the temperature gradients in the melt ahead of the columnar dendrites are in the range of -0.80 -1.0 ºC/cm for Pb-Sn alloys, -11.41-2.8ºC/cm for Al-Cu alloys, -4.2-0.67 ºC/cm for Al-Si alloys, -1.67-0.91 ªC/cm for Al-Mg alloys, -11.38-0.91 ªC/cm for Al-Zn alloys. Two interfaces are defined, assumed to be macroscopically flat, the liquidus and solidus interfaces. When the CET occurs, the sped of the liquidus front accelerates much faster than the solidus front, Also, the average supercooling was measured to be between 0.004 ªC to 2.75 ªC. The results obtained in all alloy systems are compared and analized.