Novel method of extrusion cutting for refining grain size with a movable material container

Abstract

The use of multi-movable containers for extrusion cutting of low-alloy materials can enhance the mechanical properties of cold extrusion. The grain structure becomes denser during extrusion and deformation, and the cross-sectional metal streamlines, which align with the product's geometric contour, remain continuously distributed and unbroken. However, grain size uniformity at the edges can be further improved. This study proposes the utilization of a movable extrusion die to better control the grain size, enhancing the hardening effects of the material as it enters the die through extrusion cutting. The process employs a movable and a stationary container with a step at the boundary near the die discharge port. As the material is pushed inward and downward during forming, multiple cycles induce severe plastic deformation (SPD), altering the grain direction and refining the grain structure. DEFORM-3D simulations and calculations using the Tabor equations were performed, with results subject to experimental evaluation. Both predicted and experimental increases in hardness were similar, confirming the viability of the movable container design. Additionally, the movable container was used to form a bimetal billet comprising a copper core and an aluminum shell, yielding satisfactory results. Product test results confirmed that grain refinement occurred and hardness increased in all experiments.