Prediction of Porosity and Hot Tearing in Direct Chill Casting of AZ31 Magnesium Alloy

• Published in: Transactions of the Indian Institute of Metals Vol. 76; no. 6; pp. 1509 - 1516
• Main Authors: Sai Divya, P. V., Penumakala, P. K., Nallathambi, A. K.
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.06.2023; Springer Nature B.V
• Subjects: Billet casting; Bottom casting; Casting; Chemistry and Materials Science; Corrosion and Coatings; Deformation; Direct chill casting; Heat treating; Liquid metals; Magnesium base alloys; Materials Science; Metallic Materials; Mushy zones; Original Article; Pore formation; Porosity; Shrinkage; Solidification; Strain distribution; Strain rate; Tearing; Tribology; Porosity; Secondary cooling; Direct chill casting; Magnesium alloys; Hot tearing; Solidification shrinkage
• ISSN: 0972-2815; 0975-1645
• DOI: 10.1007/s12666-022-02838-5

Hot tears that occur in the mushy zone is a major challenge for the direct chill (DC) casting process. During solidification, absence of liquid metal flow to compensate for solidification shrinkage and deformation beyond certain solid fraction results in pore formation. The pore growth under imposed strain rate is related to hot tearing. In this study, pore fraction based hot tearing model is applied to DC casting of AZ31 billet to assess the hot tearing sensitivity. The pore fractions related to the shrinkage and deformation are calculated using the dimensionless Niyama criterion ( Ny *) proposed by Monroe (J Mater Sci 8:1439–1445, 2014). Temperature and strain distribution obtained using a macroscale axis-symmetric FEM model of a DC cast billet are used to predict pore fractions. Maximum porosity is observed at the centre and locations closer to the bottom of the billet. The study on the effect of casting speed upon pore fraction indicates greater susceptibility to hot tearing at higher casting speeds.