RELATION BETWEEN AS-CAST MECHANICAL PROPERTIES, MICROSTRUCTURE AND SOLIDIFICATION CONDITIONS FOR ZNAL ALLOYS

ALICIA ESTHER ARES; RUBENS CARAM .; CARLOS E. SCHVEZOV

Modeling of Casting, Welding and Advanced Solidification Processes - XI

TMS

Lugar: Warrendale; Año: 2009; p. 659 - 666

The columnar and equiaxed mode of solidification occur when equiaxed grains can nucleateand grow ahead of the columnar front provoking the columnar to equiaxed transition (CET).The prediction of the columnar to equiaxed transition is of great interest for the evaluation anddesign of the mechanical properties of castings products. Experiments are conducted to analyzethe CET during the upward unsteady state directional solidification of Al-Zn and Zn-Al alloys,under different conditions of superheat and heat transfer efficiencies at the metal/mouldinterface. A combined theoretical and experimental approach is developed to quantitativelydetermine the solidification thermal parameters: growth rates, thermal gradients and coolingrates. The effects of solidification parameters like cooling rate, growth rate and temperaturegradient on the CET position are investigated. Although the metallurgical and micromechanicalaspects of the factors controlling microstructure, microhardness, strength and ductility of alloysare complex, it is well known that solidification processing variables are of a high order ofimportance. The present paper proposes general empirical expressions which permit thecorrelation between secondary dendrite spacings, growth rate, local solidification time andultimate tensile strength for Zn-Al alloys