System and process for formation of extrusion products
Devices and processes for performing shear-assisted extrusion include a rotatable extrusion die with a scroll face configured to draw plasticized material from an outer edge of a billet generally perpendicularly toward an extrusion orifice while the extrusion die assembly simultaneously applies a rotational shear and axial extrusion force to the billet.
1. An extrusion device for shear-assisted extrusion, comprising:
an extrusion die with a scroll face in the form of a spiral that surrounds an extrusion orifice arranged in a center of the extrusion die, the scroll face configured to spin with respect to a billet to draw plasticized billet material from an outer edge of the billet in contact with the scroll face toward the extrusion orifice while applying a simultaneous rotational shear and axial extrusion force to the billet; whereby the extrusion die is configured to extrude the plasticized billet material through the extrusion orifice yielding an extrusion product with microstructure grains in the extrusion product that are one-half the size of microstructure grains in the billet prior to extrusion.
2. The device of claim 1 , wherein the scroll face includes raised ridges that extend from a face of the extrusion die to form flow path channels that extend from an outer edge of the extrusion die toward the center of the extrusion die so as to draw the plasticized billet material from the outer edge of the billet toward the extrusion orifice as the scroll spins with respect to the billet.
3. The device of claim 2 , wherein the raised ridges are arranged in a pattern comprising at least one start on the scroll face.
4. The device of claim 1 , further comprising a container defining a chamber with a fixed mandrel disposed at a central position within the chamber, the mandrel configured to connect to and mount the billet within the chamber prior to extrusion.
5. An extrusion process, comprising the steps of:
simultaneously applying a rotational shearing force and an axial extrusion force to a billet while contacting one end of the billet with a scroll face of an extrusion die in the form of a spiral that surrounds an extrusion orifice arranged in a center of the extrusion die, the scroll face configured to spin with respect to the billet to engage and move plasticized billet material toward the extrusion orifice whereby the plastically deformed billet material flows from an outer edge of the billet through the orifice forming an extrusion product with microstructure grains one-half the size of microstructure grains in the billet prior to extrusion.
6. The process of claim 5 , wherein an extrusion pressure from the axial extrusion force is less than 50 MPa during extrusion and the billet does not require preheating before extrusion.
7. The process of claim 6 , wherein a billet feed rate is less than 0.2 inches (0.51 cm) per minute and the rotational shearing force is generated from spinning the extrusion die or the billet at a rate between 100 rpm to 500 rpm.
8. The process of claim 5 , wherein the billet contains a magnesium alloy.
9. A shear-assisted extrusion process for forming products of a desired composition from billets of a magnesium alloy comprising the steps of:
simultaneously applying a rotational shearing force and an axial extrusion force to the same location on the billet with a scroll face of an extrusion die in the form of a spiral that surrounds an extrusion orifice arranged in a center of the extrusion die, the scroll face configured to spin with respect to the billet to plasticize billet material from the billet while extruding the plasticized billet material through the orifice of the extrusion die forming an extrusion product whereby microstructure grains in the extrusion product are one-half the size of microstructure grains in the billet prior to extrusion.
10. The process of claim 9 , wherein the billet does not require preheating before extrusion.
11. The process of claim 9 , wherein an extrusion pressure from the axial extrusion force is at or below 100 MPa.