Experimental Study and Numerical Analysis of Cracking During DC Casting of Large Dimension 7075 Aluminium Billets

摘要

AA7xxx alloys are hard to cast as the chemistry of the alloys make them prone to both hot and cold cracking. The difficulty to cast sound billets increases with billet diameter due to increasing thermal gradients and associated stress build-up in the center. In this paper, 7075 0405 mm billets with varying chemical composition cast by the Low Pressure Casting technology™ have been studied using numerical modelling and industrial casting trials. The microscopic structure evolution including solidification paths and secondary phase formation has been simulated using a microstructural software and combined with semi-quantitative predictions of both hot tearing and cold cracking tendencies using process modelling software. Combined with results from industrial casting trials, the correlation between alloy chemistry and critical casting speed has been analyzed.