System and process for formation of extrusion structures

Abstract

An extrusion apparatus and process are disclosed that produce high-performance extrusion structures. The extrusion apparatus includes a shear tool that applies a rotational shear force and an axial extrusion force to the face of a billet material that plasticizes the billet material. Plasticized material is extruded through an extrusion die along the length of the inner bore of the shear tool which yields hollow and solid extrusion structures. The process refines the microstructures of the extrusion structures and extrusion materials.

What is claimed is: 
     
         1 . A shear-assisted extrusion system for production of an extrusion structure, the system comprises:
 a shear tool configured to simultaneously apply a rotational shearing force and an axial extrusion force to the face of a billet material at the shear tool/billet interface that plastically deforms the billet material, the shear tool includes an extrusion die with an orifice having a selected shape that extrudes the plasticized billet material that forms the extrusion structure with a selected shape at an axial extrusion force less than that required for extrusions performed absent the rotational shearing force.   
     
     
         2 . The system of  claim 1 , wherein the extrusion die is configured to extrude the plasticized billet material along the length of an inner bore of the shear tool in response to the axial extrusion pressure applied to the face of the billet material. 
     
     
         3 . The system of  claim 1 , further includes a mandrel configured to insert a selected depth into the inner bore of the shear tool during extrusion that allows plasticized material to flow past the mandrel along the length of the inner bore that yields a hollow extrusion structure. 
     
     
         4 . The system of  claim 3 , wherein the mandrel is a fixed mandrel or a floating mandrel, or the extrusion die is a bridge die. 
     
     
         5 . The system of  claim 1 , wherein the shear tool includes at least one surface feature disposed at an end thereof configured to engage the face of the billet during extrusion operation. 
     
     
         6 . The system of  claim 1 , further includes a heating or a cooling device disposed to heat or cool the billet material. 
     
     
         7 . The system of  claim 1 , wherein the system is configured to apply the shearing force at the shear tool/billet interface by rotation of the shear tool relative to a stationary billet, by rotation of the billet relative to a stationary shear tool, and/or by rotation of the shear tool at a rotation speed that is different relative to the rotation of the billet or vice versa. 
     
     
         8 . A shear-assisted extrusion process for production of an extrusion structure or product, the process comprising the steps of:
 applying a rotational shearing force and an axial extrusion force to the face of the billet material with a shear tool at the shear tool/billet interface at a selected rotation speed to plastically deform the billet material; and   extruding the plasticized material through an orifice of an extrusion die of the shear tool that includes a selected shape to form the extrusion structure or product with a selected shape at an axial extrusion force less than that required for extrusions performed absent the rotational shearing force.   
     
     
         9 . The process of  claim 8 , wherein the plasticized billet material extrudes along the length of the inner bore of the shear tool in response to the axial extrusion pressure applied to the face of the billet material. 
     
     
         10 . The process of  claim 8 , further including introducing a mandrel into the inner bore of the ram tool to a selected depth such that the plasticized material extrudes through the orifice of the extrusion die past the mandrel along the length of the inner bore of the shear tool producing a hollow extrusion structure with a selected shape. 
     
     
         11 . The process of  claim 10 , wherein the extrusion is performed with a fixed mandrel or a floating mandrel, or the extrusion is performed with a stationary bridge die. 
     
     
         12 . The process of  claim 8 , wherein applying the rotational shear force includes engaging the billet material with the shear tool that includes a feature disposed at the end thereof. 
     
     
         13 . The process of  claim 8 , wherein the extrusion structure includes a uniform inner wall thickness, a uniform inner dimension, and a selected shape; or a non-uniform inner wall thickness, a non-uniform inner dimension, and a selected shape. 
     
     
         14 . The process of  claim 8 , wherein the process includes heating or cooling the billet material with a selected heating device and/or cooling device. 
     
     
         15 . The process of  claim 8 , wherein the process includes heating the plasticized billet material with frictional heat generated during deformation of the billet material. 
     
     
         16 . The process of  claim 8 , wherein extrusion of the plasticized billet material is performed at a temperature selected between about −196° C. and about 0° C.; or between about 0° C. and about 1000° C.; or greater. 
     
     
         17 . The process of  claim 8 , wherein the rotational shear force is applied by rotating the billet at a selected rotational speed while keeping the shear tool stationary, by rotating the shear tool at a selected rotational speed while keeping the billet material stationary, or by rotating the shear tool at a selected rotational speed different than the rotational speed of the billet material or vice versa. 
     
     
         18 . The process of  claim 17 , wherein the selected rotational speed is up to about 1000 revolutions-per-minute. 
     
     
         19 . The process of  claim 8 , wherein the axial extrusion pressure is at or below about 50 MPa. 
     
     
         20 . The process of  claim 8 , wherein the process includes altering the morphology of second-phase particles in the billet material from an aspect ratio above about 2 prior to extrusion to an aspect ratio below about 2 following extrusion. 
     
     
         21 . The process of  claim 8 , wherein the process yields microstructure grains in the extrusion structure or product at least about one-half the size of the grains prior to extrusion. 
     
     
         22 . The process of  claim 8 , wherein the process yields microstructure grains with a size less than or equal to about 10 microns, less than or equal to about 5 microns, or finer. 
     
     
         23 . The process of  claim 8 , wherein the extrusion structure is a tubular extrusion structure included as a component of a compression device, a stent device, a bending resistant device, including combinations of these devices.