Initial Development of Micro-Shrinkage Crack During Early Stages of Direct Chill Casting of Al-4.5% Cu Alloy

Abstract

An investigation has been carried out under controlled laboratory conditions designed to approximate the conditions encountered during the early stages of direct chill of Al-4:5 % Cu aluminum alloy ingots to study the formation of micro-shrinkage crack. Also, a couple models have been established at the author's organization to compute convection patterns, thermal fields, interdendritic thermo-metallurgical strain and macrosegregation distributions. Comparisons between the available microstructure taken from the samples and model predictions of convection streams to verify the mechanism of the random sedimentation of free crystals and therefore the micro-shrinkage crack formation were performed where good agreements were obtained. The effects of convection streams of various melt superheats at different locations in the aluminum ingots on the formation micro-shrinkage crack have been studied and analyzed. The mechanism of micro-shrinkage crack formation with different convection streams patterns and superheats were also discussed.