SOLIDIFICATION, MACROSTRUCTURE AND MICROSTRUCTURE ANALYSIS OF AL-CU ALLOYS DIRECTIONALLY SOLIDIFIED FROM THE CHILL FACE

ALICIA ESTHER ARES; CARLOS ENRIQUE SCHVEZOV

San Francisco, California, USA

Simposio; Shape Casting: Third International Symposium; 2009

The Metallurgical Society of AIME

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-US; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The understanding of the phenomenon of the Columnar to Equiaxed Transition (CET) is very important for metallurgical applications. In the present study the CET was observed in aluminum-copper alloys of different compositions (Al-2wt%Cu, Al-20wt%Cu and Al-33.2wt%Cu, which were solidified directionally from a chill face. The main parameters analyzed include cooling rates, temperature gradients, solidification velocities of the liquidus fronts, recalescence, grain size, primary and secondary dendritic arm spacing and eutectic spacing. The temperature gradient and the velocity of the liquidus front reach low critical values before the transition. These critical values are between 0.4 to 3.8 mm.s-1 for the velocity and -0.44 to 0.10 K.mm-1 for the temperature gradient. In the case of the eutectic alloys, the transition from columnar to equiaxed occurs with similar characteristics as for the other concentrations, the resultant lamellar, rod-like or mixed solidification microstructure have parameters which also depend on solidification conditions, mainly velocity.