Influence of extrusion temperature on deformation behavior of Csf/AZ91D composite during semi-solid extrusion

Deformation behavior and formability of Csf/AZ91D magnesium composite were investigated by semi-solid extrusion between 695 K and 728 K, including temperatures below and above the partial melting temperature. A method of constructing kinematically admissible velocity fields for axisymmetric extrusion based on the theory of flow function was proposed. Flow lines were analyzed in Csf/AZ91D composite after extrusion at elevated temperatures. Based on an analytic flow function, the deformation field was obtained. The results show that when the composite is extruded in a semi-solid state containing a small volume of liquid, the presence of the liquid reduces deformation resistance by relaxing the stress concentrations, and improves the formability of composites as lubricant. However, the gradient of velocity field is increased and deformation uniformity is aggravated at temperatures greater than partial melting point at 701.3 K. A more uniform deformation field was attained at the temperature close to or slightly below the partial melting temperature.

Research highlights▶ A new analytical flow line model was carried out to investigate plastic deformation. ▶ Deformations of Csf/AZ91D composite extruded between 695 K and 728 K were investigated. ▶ The excellent formability was attained containing a continuous liquid. ▶ The higher deformation uniformity develops adjacent to solidus temperature.