The Importance of Viscoplastic Strain Rate in the Formation of Center Cracks during the Start-Up Phase of Direct-Chill Cast Aluminum Extrusion Ingots

摘要

A comparison of experimental observations and computer simulations shows that trends in the occurrence and severity of center cracks in direct-chill (DC) cast ingots due to different initial casting speed histories may best be explained by the changes in viscoplastic strain rate close to the center of the base of the ingot. The thermomechanical histories of five ingots were simulated and correlations between stresses, strains, strain rates, and liquid pressure drops due to feeding restrictions were considered.