Mechanical Behavior of Mushy Zone in DC casting using a Viscoplastic Material Model
Direct Chill (DC) casting is a semi-continuous metal manufacturing process for producing non-ferrous alloys such as aluminum and magnesium. During the solidification of the alloy, there exists a semi-solid state of material known as mushy zone which is more prone to hot tearing. Precise modeling of hot tearing is the most challenging task due to the interaction of many physical fields. The deformation of the partially coherent solid strongly influences the hot cracking. This work focuses on the material behavior of the mushy zone which is the prerequisite for the development of hot tearing criteria. The rate-dependent nature plays a crucial role at higher temperatures. Therefore, the viscoplastic material models with temperature-dependent coefficients are implemented for the characterization of the mushy zone. The numerical integration of the constitute equations are explained in detail. The liquid flow is neglected, and the momentum and energy equations are solved for the mushy and solid phases. With the help of a viscoplastic material models, the stress and strain evolution in the mushy zone is captured. It is found that the state of stress in mushy region is tensile in nature which is a favorable situation for the hot cracks. The influence of the casting speed and secondary cooling on the mushy stress state are analyzed in detail.