U.S. patent application number 14/222468 was filed with the patent office on 2014-09-25 for system and process for formation of extrusion structures.
This patent application is currently assigned to BATTELLE MEMORIAL INSTITUTE. The applicant listed for this patent is Richard W. Davies, Glenn J. Grant, Darrell R. Herling, Saumyadeep Jana, Vineet V. Joshi, Curtis A. Lavender, Dean M. Paxton. Invention is credited to Richard W. Davies, Glenn J. Grant, Darrell R. Herling, Saumyadeep Jana, Vineet V. Joshi, Curtis A. Lavender, Dean M. Paxton.
Application Number | 20140283574 14/222468 |
Document ID | / |
Family ID | 51568135 |
Filed Date | 2014-09-25 |
United States Patent
Application |
20140283574 |
Kind Code |
A1 |
Lavender; Curtis A. ; et
al. |
September 25, 2014 |
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.
Inventors: |
Lavender; Curtis A.;
(Richland, WA) ; Joshi; Vineet V.; (Richland,
WA) ; Paxton; Dean M.; (Kennewick, WA) ; Jana;
Saumyadeep; (Kennewick, WA) ; Grant; Glenn J.;
(Benton City, WA) ; Herling; Darrell R.;
(Richland, WA) ; Davies; Richard W.; (Pasco,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lavender; Curtis A.
Joshi; Vineet V.
Paxton; Dean M.
Jana; Saumyadeep
Grant; Glenn J.
Herling; Darrell R.
Davies; Richard W. |
Richland
Richland
Kennewick
Kennewick
Benton City
Richland
Pasco |
WA
WA
WA
WA
WA
WA
WA |
US
US
US
US
US
US
US |
|
|
Assignee: |
BATTELLE MEMORIAL INSTITUTE
Richland
WA
|
Family ID: |
51568135 |
Appl. No.: |
14/222468 |
Filed: |
March 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61804560 |
Mar 22, 2013 |
|
|
|
Current U.S.
Class: |
72/262 ; 72/269;
72/271 |
Current CPC
Class: |
B21C 23/218 20130101;
B21C 23/002 20130101; B21C 27/00 20130101; B21C 29/003 20130101;
B21C 23/212 20130101 |
Class at
Publication: |
72/262 ; 72/271;
72/269 |
International
Class: |
B21C 23/00 20060101
B21C023/00; B21C 29/00 20060101 B21C029/00 |
Goverment Interests
STATEMENT REGARDING RIGHTS TO INVENTION MADE UNDER
FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
[0002] This invention was made with Government support under
Contract DE-AC05-76RLO-1830 awarded by the U.S. Department of
Energy. The Government has certain rights in the invention.
Claims
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.degree. C. and about 0.degree. C.; or between about
0.degree. C. and about 1000.degree. 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.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a Non-Provisional application that claims priority
from U.S. Provisional Application No. 61/804,560 filed 22 Mar.
2013, which reference is incorporated herein in its entirety.
FIELD OF THE INVENTION
[0003] The present invention relates generally to extrusion
processing and extrusion tools. More particularly, the invention
relates to a shear-assisted extrusion system and process for
production of extrusion structures including high-performance
extrusion structures.
BACKGROUND OF THE INVENTION
[0004] Extrusion is a process in which a billet or block of
material composed of metals, polymers, ceramics, or foodstuffs is
forced through an extrusion die with a ram tool that transmits an
extrusion force to the billet that plasticizes the material. The
plasticized material is then extruded through the orifice of an
extrusion die that forms an extrusion product (extrudate). The
resulting extrusion product has a cross-sectional area or profile
that is typically smaller than that of the original billet. In
conventional extrusion, only the linear or axial motion of the ram
plasticizes and extrudes the billet material. Extrusion processes
fall under two general categories: (i) direct extrusion, and (ii)
indirect extrusion. In direct extrusion, the extrusion die and a
solid ram are positioned on opposite ends of the billet. In
indirect extrusion, the extrusion die is attached to a hollow ram
on the same side of the billet. A mandrel may be attached to the
hollow ram during extrusion of the billet material to produce
hollow extrudates. Problems with extrusion processing are well
known in the art. Conventional extrusion requires high extrusion
pressures on the order of 400 MPa or higher. In addition,
non-uniform deformation of extrudates is common, which yields
extrusion products with structural and physical property variations
in both the longitudinal and transverse directions. Further,
microstructure refinement is often inconsistent and typically
insufficient so mechanical properties vary widely. And, while
processes like mechanical alloying, rapid solidification, friction
stir processing, equal channel angular extrusion, twist extrusion,
waffle pattern rolling, non-axis symmetric rolling, and other
processes have been used to make high performance materials, such
processes are not presently cost-effective for commercial
production. Accordingly, new extrusion processing tools and
processes are needed that overcome conventional force requirements
and other limitations of conventional extrusion processing. The
present invention addresses these needs. The purpose of the
foregoing abstract is to enable the United States Patent and
Trademark Office and the public generally, especially scientists,
engineers, and practitioners in the art who are not familiar with
patent or legal terms or phraseology, to determine quickly from a
cursory inspection the nature and essence of the technical
disclosure of the application. The abstract is neither intended to
define the invention of the application, which is measured by the
claims, nor is it intended to be limiting as to the scope of the
invention in any way.
SUMMARY OF THE INVENTION
[0005] The present invention includes an extrusion assembly and
process for production of high-performance extrusion structures and
extrusion products. The extrusion assembly may include a shear tool
with an extrusion die of a selected shape. The shear tool is
configured to apply a rotational shear (shearing) force and an
axial extrusion pressure to the face of a billet material at the
shear tool/billet interface positioned within the die chamber of
the extrusion assembly that plastically deforms the billet
material. The billet may include various selected materials
including, but not limited to, e.g., metals, metal alloys, cast
solids, powders, and non-solids. The extrusion die may be
positioned at the billet end of the shear tool and may include an
orifice with a selected shape and selected dimensions. The
extrusion die may extrude the plasticized billet material 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 yielding
extrusion structures and products with selected shapes including
complex shapes with selected dimensions. The inner bore of the
shear tool may include selected dimensions. The shear tool forms
extrusion structures and products at an axial extrusion pressure
significantly lower than required for extrusion structures without
the shearing force applied. The extrusion die may extrude the
plasticized billet material 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.
[0006] The present invention also includes a shear-assisted
extrusion process that produces extrusion structures including
high-performance extrusion structures. The process may include
applying a rotational shearing force and an axial extrusion force
to the face of the billet material at the shear tool/billet
interface to plasticize the billet material. The shearing force may
be applied at the shear tool/billet interface by rotation of the
shear tool at a selected rotation speed relative to a stationary
billet, or 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.
The plasticized material may be extruded the through an orifice of
an extrusion die positioned on the billet side of the shear tool.
The orifice of the extrusion die may include various selected shape
that yield extrusion structures with selected shapes. Rotational
shear force values are not limited. Shear forces are selected that
reduce the axial extrusion pressures needed to plasticize billet
materials. The extrusion assembly extrudes the billet material at
an axial extrusion force less than that required for extrusions
performed without the rotational shearing force applied by the
shear tool and/or the billet at the shear tool/billet
interface.
[0007] In some applications, the billet may be a pierced cast
billet, a pre-drilled cast billet, a solid cast billet, or loose
powder billets.
[0008] Extrusion structures may be hollow or solid. The extrusion
assembly may include a mandrel that inserts into the inner bore of
the shear tool to a selected depth. In some applications, the
mandrel may be introduced through the center of the billet and into
the inner bore through an orifice of the extrusion die positioned
at the billet end or other end of the shear tool. The mandrel may
include a width dimension that is less than the dimension of the
orifice of the extrusion die that forms a separation gap between
the surface of the mandrel and the inner wall of the extrusion die
when the mandrel is inserted. During extrusion, the separation gap
allows plasticized materials to flow past the mandrel along the
length of the inner wall of the extrusion die and into the inner
bore of the shear tool that yields hollow extrusion structures with
selected shapes. The extrusion die determines the wall thickness of
hollow extrusion structures produced during extrusion.
[0009] Shapes are not limited. In various applications, extrusion
structures may be hollow tubular structures with selected uniform
or non-uniform inner dimensions and selected uniform or non-uniform
wall thicknesses. In various applications, extrusion structures may
be solid extrusion structures with selected uniform or non-uniform
cross-sections. No limitations are intended.
[0010] In some applications, the mandrel may be a fixed mandrel or
a floating mandrel. In some applications, the extrusion die may be
a bridge extrusion die. However, mandrels and extrusion dies are
not limited thereto.
[0011] The shear tool may include one or more surface features
positioned at the billet end of the shear tool that engage the face
of the billet material to facilitate shear-assisted extrusion and
flow of plasticized materials during operation. Features may
include, but are not limited to, e.g., scrolls, flutes, vanes, or
other features including combinations of these features.
[0012] In some applications, the extrusion assembly may include a
heating device such as an external heating device or an embedded
heating device and/or a cooling device positioned to heat or cool
the billet material positioned within the die chamber,
respectively. Billet materials may also be heated using the
frictional heat generated from the plastically deformed billet
materials.
[0013] Extrusion temperatures are not limited. In some
applications, extrusion of the plasticized billet material may be
performed at a temperature selected between about -196.degree. C.
and about 0.degree. C. In some applications, extrusion of the
plasticized billet material may be performed at a temperature
selected between about 0.degree. C. and about 1000.degree. C., or
greater.
[0014] Shearing forces applied by the present invention may be
obtained by rotating the billet while keeping the shear tool
stationary, by rotating the shear tool while keeping the billet
material stationary, or by rotating the shear tool at a rotational
speed different than the rotational speed of the billet material or
vice versa.
[0015] In some applications, applying the rotational shear force
and extruding the plasticized billet material may be performed
simultaneously. In some applications, applying the rotational shear
force and extruding the plasticized billet material may be
performed independently from the other step.
[0016] In some applications, axial extrusion pressures required for
extrusion may be reduced by at least a factor of about 16 times
compared to extrusion operations performed without the rotational
shearing force. In some applications, the axial extrusion pressure
is at or below about 50 MPa. In some applications, the axial
extrusion pressure is at or below about 25 MPa. However, axial
pressures are not limited.
[0017] Feed rates for the billet are not limited. In some
applications, feed rates may be between about 0.15 inches (0.38 cm)
per minute and about 1.18 inches (3.0 cm) per minute.
[0018] Rotational speeds are not limited. In various applications,
rotation may be performed at a rotation speed between about 500
revolutions-per-minute (rpm) and about 1000 rpm. In some
applications, rotation may be performed at a rotation speed up to
about 1000 rpm. In some applications, rotation speed may be between
about 10 rpm and about 1000 rpm.
[0019] Shear-assisted extrusion processing of the present invention
can refine the microstructure of billet materials including cast
billet materials and powdered billet materials, or other processed
materials. For example, billets containing coarse matrix grains and
second-phase intermetallic particles with sizes up to a millimeter
(1000 microns) may be refined in a single process step to yield
smaller grains and particles. In some applications, the process
refines the microstructure to yield fine matrix grains and
second-phase intermetallic particles with a size less than or equal
to about 10 microns. In some applications, the process yields very
(ultra) fine matrix grains and second-phase intermetallic particles
with a size less than or equal to about 1 micron or finer. In some
applications, the process yields grains with a size less than about
100 nanometers or finer. However, no limitations are intended. In
some applications, the present invention alters the morphology of
second-phase particles in the starting billet material from an
aspect ratio above about 2 to an aspect ratio below about 2
following the shear-assisted extrusion processing. In some
applications, microstructure grains and particles of the original
billet material are refined by at least a factor of 2 times to a
size that is at least one-half that of the original billet material
prior to extrusion processing or finer. Shear-assisted extrusion
processing can also uniformly distribute grains and particles
within the refined microstructure.
[0020] In some applications, extrusion structures are tubular
extrusion structures that may be included as components of a
compression device, a stent device, a bending-resistant device.
Compression devices include, but are not limited to, e.g.,
compression bumpers or collapsible safety frames deployed in
automobiles. In various applications, extrusion structures of the
present invention may be incorporated as components of selected
structures such as in support pillars or other structures deployed
in vehicles to enhance mechanical properties, performance, or to
resist bending. In some applications, extrusion structures may be
included as components of a stent device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is an isometric external view of an extrusion
assembly of an indirect extrusion type, according to one embodiment
of the present invention.
[0022] FIG. 2 shows exemplary internal and external components of
the extrusion assembly.
[0023] FIG. 3A is a cross-sectional view of the extrusion assembly
of FIG. 1.
[0024] FIG. 3B is an expanded view of the embodiment of FIG.
3A.
[0025] FIG. 3C shows a cross-sectional view of an extrusion
assembly of a direct extrusion type, according to another
embodiment of the present invention.
[0026] FIG. 4 is a perspective view of a shear tool that includes a
scroll feature.
[0027] FIG. 5 compares extrusion pressure data for conventional
indirect extrusion and shear-assisted extrusion of the present
invention.
[0028] FIG. 6 shows exemplary tubular extrusion structures produced
by the process of the present invention.
[0029] FIG. 7 is a photomicrograph showing grains and particles in
the extrusion structure following extrusion processing.
DETAILED DESCRIPTION OF THE INVENTION
[0030] A new shear-assisted extrusion apparatus and process are
disclosed for producing high-performance extrusion structures
including, e.g., hollow and solid extrusion structures. In the
following description, embodiments of the present invention are
shown and described that include a best mode contemplated for
carrying out the invention. It will be clear from the following
description that the invention is susceptible of various
modifications and alternative constructions. The present invention
is intended to cover all modifications, alternative constructions,
and equivalents falling within the spirit and scope of the
invention as defined in the claims. Therefore the description
should be seen as illustrative and not limiting.
[0031] FIG. 1 shows an extrusion assembly 100 of an indirect
extrusion type for production of high-performance extrusion
structures. Extrusion assembly 100 may include a shear tool 2 that
is configured to apply a rotational shear (shearing) force 26 and
an axial extrusion force 24 to the face of a billet material (not
shown) positioned within a die chamber 10 that assists
plasticization of the billet material. Extrusion assembly 100 and
shear tool 2 may be constructed of, e.g., steel alloys (e.g., H-13
tool steel), titanium alloys, nickel alloys, and combinations of
these materials that resist physical and chemical wear at a wide
range of temperatures, are mechanically strong, and effectively
distribute heat through the billet during extrusion processing.
[0032] Extrusion assembly 100 may include a container 8 comprised
of, e.g., an upper container plate 7 and a lower container plate 9.
Container 8 may also be a single component. No limitations are
intended. In the instant embodiment, outer (top) die ring 14 and a
lower die ring (described further in reference to FIG. 2) couple
together to form die chamber 10. Die chamber 10 may also be a
single machined component. Again, no limitations are intended. The
billet (described hereafter in reference to FIG. 3) may be
positioned within die chamber 10 to provide aligned contact with
shear tool 2 when shear tool 2 is introduced into die chamber 10
during operation.
[0033] Shear tool 2 may include an inner bore 4 of a selected inner
dimension with orifices 5 positioned at respective ends of shear
tool 2. Outer (top) die ring 14 and lower die ring (not shown)
secure shear tool 2 in die chamber 10. Outer die ring 14 may be
secured with locking keys (not shown) that insert into key slots 20
positioned on respective sides of shear tool 2. Position and number
of key slots 20 is not limited. During operation, plasticized
billet materials extrude along the length of inner bore 4 and exit
from an orifice 5 of shear tool 2 as extrusion structures
(extrudates) 6. Direction of release of extrudates is not limited,
as detailed further herein.
[0034] FIG. 2 is a three-dimensional view of die assembly 100
showing selected internal components. In the figure, outer (top)
die ring 14 is shown positioned atop bottom (base) die ring 16.
Keys (not shown) described previously in reference to FIG. 1 insert
into key slots 20 positioned on opposite sides of outer die ring 14
that lock top die ring 14 and bottom die ring 16 together. A
mandrel 28 is shown positioned at the base of die chamber 10.
Mandrels may include, e.g., fixed mandrels and floating mandrels.
Mandrel 28 may insert into inner bore 4 of shear tool 2, e.g., from
the billet end of shear tool 2. Mandrel 28 may direct flow of
extruded billet materials along the length of inner bore 2.
Extruded materials may release through an orifice 5 positioned,
e.g., at a top end of shear tool 2. However, release is not limited
thereto, as detailed further herein.
[0035] FIG. 3A is a cross-sectional view of extrusion assembly 100
of an indirect extrusion type described previously in reference to
FIG. 1. Extrusion assembly 100 is shown in assembled form with the
flow of plasticized billet material illustrated during extrusion
operation. In the figure, outer die ring 14 and lower die ring 16
couple together to form die chamber 10. In some embodiments, die
chamber 10 may also be a single machined component. Die chamber 10
may be assembled within the container between, e.g., upper
container plate 7 and lower container plate 9. In some embodiments,
the container may also be a single component. In the figure, billet
22 is shown positioned within die chamber 10 to provide aligned
contact with shear tool 2 when shear tool 2 is introduced into die
chamber 10. A mandrel 28 described previously in reference to FIG.
2 may be positioned in chamber 10, which may insert to a selected
depth in inner bore 4 of shear tool 2 during assembly through an
optional spacer (e.g., a graphite spacer) 32 through billet 22 and
through an orifice 5 of an extrusion die 11. Extrusion die 11 may
be positioned at the billet end of shear tool 2. Extrusion dies are
not limited. In some embodiments, a bridge die may be employed.
Orifice 5 of extrusion die 11 may include selected shapes described
further herein. The extrusion die determines at least in part the
shape of extrusion structures produced during extrusion operation.
Mandrel 28, optional spacer 32, and billet 22 may be secured in
chamber 10 by introducing locking keys (described previously) into
key slots 20 positioned on respective sides of outer die ring 14 as
described previously herein.
[0036] In operation, shear tool 2 when introduced into chamber 10
applies a rotational shear (shearing) force 26 and an axial
extrusion force 24 to the face of billet material 22 at the shear
tool/billet interface within die chamber 10. Rotational shear
(shearing) force 26 assists or promotes plasticization of billet
material 22. In some embodiments, rotational shear (shearing) force
26 may be applied by rotating the shear tool 2 at a selected
rotation speed while keeping billet 22 stationary. In some
embodiments, rotational shear (shearing) force 26 may be applied by
rotating the billet 22 while keeping shear tool 2 stationary. In
some embodiments, rotational shear (shearing) force 26 is applied
by rotating shear tool 2 and billet 22 at different rotation speeds
relative to the other component or material.
[0037] Die assembly 100 may further include an optional
heater/cooler 36 that couples externally to, or is embedded within,
outer die ring 14 to heat or cool billet material 22 positioned
within chamber 10. Heating and cooling of billet material 22 can be
used to assist deformation of billet material 22, e.g., by
softening the billet material in cases where the billet material
shows limited initial plasticity. Heating may also be used, e.g.,
to lower frictional forces that assist extrusion of the plasticized
billet material. All heating and cooling devices as will be
selected by those of ordinary skill in the art in view of this
disclosure are within the scope of the present invention. No
limitations are intended.
[0038] Application of axial extrusion force 24, rotational shear
force 26, and/or heat or cooling to billet material 22 plasticizes
the billet material, which forms a region of plastic deformation
(SPD) 34 positioned at the shear tool/billet interface. SPD region
34 is typically narrow (e.g., <300 microns) to reduce extrusion
force 24 needed to extrude the plasticized billet materials.
[0039] Plasticized billet materials may enter into inner bore 4
through an orifice (not shown) positioned, e.g., at the billet end
of shear tool 2. In the instant embodiment, plasticized material
extrudes past mandrel 28 and flows upward to yield extrusion
structures (extrudates) 6 that are hollow extrusion structures
(e.g., tubes). In some embodiments, extrusion structures may
include uniform inner dimensions and wall thicknesses. In some
embodiments, extrusion structures may include non-uniform inner
dimensions and wall thicknesses. When mandrel 28 is not employed,
extrusion structures are solid structures. Solid extrusion
structures may include uniform dimensions or non-uniform
dimensions. In the instant embodiment, extrusion structures
(extrudates) 6 may be released through another orifice 5 positioned
at the top end of shear tool 2.
[0040] FIG. 3B shows an expanded view of the die assembly 100 of
FIG. 3A. As shown in the figure, plasticized billet materials may
flow from deformation region 34 through a gap 30 formed between the
surface of mandrel 28 and the inner wall of extrusion die 11. Other
components of extrusion assembly 100 including billet 22 positioned
in chamber 10, optional spacer 32, upper die ring 14, and lower die
ring 16 have been described previously herein.
[0041] FIG. 3C is a cross-sectional view of another embodiment of
extrusion assembly 100 of a direct extrusion type. Die assembly 100
is shown in assembled form and also shows flow of plasticized
billet material during extrusion operation. In the figure, die
assembly 100 includes a billet rotation tool or device, e.g., die
ring 16, configured to apply rotational shear force 26 to the
billet material 22 positioned within die chamber 10. Billet
material 22 may be in aligned contact with tool 2 or a die support.
A mandrel 28 described previously in reference to FIG. 3A may be
positioned in chamber 10, which may insert to a selected depth in
inner bore 4 of shear tool 2 during assembly through an optional
spacer (e.g., a graphite spacer) 32 through billet 22 and through
an orifice (not shown) of extrusion die 11 positioned at the billet
end of shear tool 2. Extrusion dies are not limited. In some
embodiments, a bridge die may be employed. In operation, billet
rotation tool 16 applies a rotational shear (shearing) force 26 and
an axial extrusion force 24 to the face of billet material 22 at
the shear tool/billet interface within die chamber 10. Extrusion
assembly 100 may further include an optional heater/cooler (not
shown) described previously in reference to FIG. 3A. Application of
axial extrusion force 24, rotational shear force 26, and/or heat or
cooling to billet material 22 plasticizes the billet material,
which forms a region of plastic deformation (SPD) 34 positioned at
the shear tool/billet interface. SPD region 34 is preferably narrow
(e.g., <300 microns) to reduce the extrusion force 24 needed to
extrude plasticized billet materials. Plasticized billet materials
may flow downward from deformation region 34 and extrude through an
orifice 5 of extrusion die 11 that is positioned at the billet end
of tool 2 into inner bore 4. Plasticized billet materials may then
flow through gap (FIG. 3B) formed between the external surface of
mandrel 28 and the inner wall (not shown) of extrusion die 11. In
the instant embodiment, plasticized material extrudes past mandrel
28 and flows downward to yield extrusion structures (extrudates) 6
that are hollow extrusion structures (e.g., tubes). In some
embodiments, extrusion structures may include uniform inner
dimensions and wall thicknesses. In some embodiments, extrusion
structures may include non-uniform inner dimensions and wall
thicknesses. When mandrel 28 is not employed, extrusion structures
are solid structures. Solid extrusion structures may include
uniform dimensions or non-uniform dimensions. In the instant
embodiment, extrusion structures (extrudates) 6 may be released
through another orifice 5 positioned at the bottom end of tool
2.
[0042] FIG. 4 is a perspective view showing an exemplary
configuration for shear tool 2. In the instant embodiment, shear
tool 2 includes a scroll feature 38 positioned at an end (face) of
shear tool 2 that engages the face of the billet (FIG. 3) to
facilitate shear-assisted extrusion and flow of plasticized
materials. Features include, but are not limited to, e.g., scrolls,
flutes, vanes, and like features. Number of features and types of
features are not intended to be limited.
Billets
[0043] Billets may be in the form of solids, cast solids, blocks,
semi-solids, non-solids, and/or powders. Cast billets may be cast
using casting techniques known in the casting arts. Billets may be
composed of, or include, any material that can be plastically
deformed (plasticized) at selected temperatures. Billet materials
are preferred that deliver desirable mechanical properties such as
ductility, compression strength, bendability, or selected
microstructural refinement, or other suitable properties to the
extrusion structures or products produced. However, no limitations
are intended. In various embodiments, billets may include or be
constructed of various materials including selected alloys and
high-performance alloys. In some embodiments, billets may employ
magnesium alloys. Magnesium alloys include, but are not limited to,
e.g., magnesium alloys (e.g., AZ31F); magnesium-aluminum (Mg--Al)
alloys; magnesium-zinc (Mg--Zn) alloys; magnesium-zirconium
(Mg--Zr) alloys; magnesium-silicon (Mg--Si) alloys (e.g., Mg-2Si;
Mg-7Si); magnesium alloys that include rare-earth (RE) elements;
magnesium alloys that include various non-rare-earth elements;
magnesium-zinc-zirconium alloys (e.g., ZK60-T5), and combinations
of these various alloys. While magnesium-based alloys are described
herein due to their desirable ductility properties for compression
applications, the present invention is not intended to be limited
thereto. In some embodiments, billets used for extrusion may
include a central bore or hollow cavity through which the mandrel
may be introduced during extrusion. In some embodiments, billets
may be solid billets that are pierced or predrilled prior to
use.
Extrusion Shapes
[0044] The shear tool of the present invention may include an
extrusion die that includes an inner bore with various selected
shapes that delivers extrusion structures with selected shapes
including complex shapes. Shapes include, but are not limited to,
e.g., round, oval, circular, square, rectangular, triangular,
pentagonal, hexagonal, octagonal, ellipsoidal, trapezoidal,
rhombal, or combinations of these various shapes. Complex shapes
include, but are not limited to, e.g., spherical, tetrahedral,
pyramidal, pentagonal, pentagonal pyramidal, irregular, ortahedral,
icosahedral, dedecahedral, stars, cones, boat-shape ovals,
parallelograms, rounded rectangles, chevrons, round left, round
right, bent arrows, arrows, double arcs, curved, obround, single-D,
double-D, long-D, quad-D, letters, numerical, alpha-numerical,
symmetrical shapes, non-symmetrical shapes, oblong shapes, rings,
pictoral shapes, other non-standard shapes, including, e.g.,
embedded shapes such as, e.g., ovals within a square, squares
within an oval, and like embedded shapes. All shapes as will be
selected by those of ordinary skill in the art in view of the
disclosure are within the scope of the present invention. No
limitations are intended.
Process Parameters
[0045] TABLE 1 lists compositions of alloy billets and process
parameters employed in selected extrusion tests.
TABLE-US-00001 TABLE 1 Test Matrix for selected extrusion
structures of the present invention. Ram Rotation Feed Rate Test
No. Alloy (rpm) (inches/min) 1 Mg--2Si 500 0.15 2 Mg--7Si 500 0.15
3 AZ31F 500 0.15 4 ZK60-T5 500 0.15
[0046] Billet feed rates are not limited. Feed rates may be
selected that maximize extrusion throughput, plasticity, flow,
uniformity of the extrudates, and other physical and mechanical
properties. In some embodiments, feed rates for billet deformation
may be greater than about 0.01 inches per minute. In some
embodiments, feed rates for billet deformation may be between about
0.01 inches per minute and about 0.1 inches per minute. In some
embodiments, feed rates for billet deformation may be between about
0.1 inches per minute and about 1.0 inches per minute. In some
embodiments, feed rates for billet deformation may be between about
1.0 inches per minute and about 10 inches per minute.
Rotation
[0047] Rotation rates for the rotatable shear tool or the billet
are not limited. In some embodiments, rotation may proceed at a
rate up to about 1000 revolutions-per-minute (rpm). In some
embodiments, rotation speed may be between about 50 rpm and about
500 rpm. In some embodiments, the process may include rotating the
ram at a rate between about 500 rpm and about 1000 rpm.
Extrusion Temperatures
[0048] Extrusion temperatures are not limited. Temperatures may be
selected that maximize shear on the face of the billet, plastic
deformation of the selected billet materials, microstructure
refinement, and other physical and mechanical properties. In some
embodiments, extrusion may be performed at temperatures above about
100.degree. C. In some embodiments, extrusion may be performed at
temperatures between about 100.degree. C. and about 500.degree. C.
In some embodiments, extrusion may be performed at temperatures
between about 500.degree. C. and about 1000.degree. C. In some
embodiments, extrusion may be performed at temperatures above about
1000.degree. C. In some embodiments, extrusion may be performed at
temperatures below about 100.degree. C. In some embodiments,
extrusion may be performed at temperatures between about 0.degree.
C. and about -100.degree. C. In some embodiments, extrusion may be
performed at temperatures between about -100.degree. C. and about
-196.degree. C. (the temperature of liquid nitrogen). No
limitations are intended. In other embodiments, temperatures may be
selected that are identified from equilibrium phase diagrams of the
selected alloys or the billet materials being processed. No
limitations are intended.
[0049] FIG. 5 plots extrusion pressure (axial load/billet cross
sectional area) against the displacement (i.e., depth) of the shear
tool. Data in the figure compare axial extrusion pressure (force)
for shear-assisted extrusion processing of the present invention
against conventional extrusion applied to the face of a 1.25''
(3.18 cm) diameter magnesium alloy billet [e.g., a ZK60 grade
magnesium-zinc-zirconium (Mg--Zn--Zr) alloy, Luoyang Kunyao Metal
Material Co., Ltd., Luoyang, China]. As shown, significantly higher
extrusion pressures are required for the extrusion performed absent
the shear tool when compared to the shear-assisted extrusion.
Maximum process pressure applied by the shear tool during
shear-assisted extrusion is less than about 20 MPa at a shear tool
displacement of 0.13 inches (0.32 cm). By comparison, conventional
extrusion processing requires an extrusion pressure greater than
about 400 MPa (e.g., 430 MPa) and a temperature of 350.degree. C.
(i.e., when billets are already soft), a factor of 16 times greater
than shear-assisted extrusion processing of the present invention.
In some embodiments, the present invention employs an extrusion
pressure below about 50 MPa. In some embodiments, shear-assisted
extrusion processing employs an extrusion pressure below about 25
MPa. Dimensions of hollow extrusion structures including the inner
bore dimension and inner wall thickness are not limited. Extrusion
structures may also be solid structures. Cross sectional
dimensions, shapes, and length dimensions are not limited. TABLE 2
lists dimensions of exemplary hollow extrusion structures of the
present invention obtained in selected extrusion tests from
selected alloy billets. FIG. 6 shows photos of the tubes
obtained.
[0050] TABLE 2 lists results obtained from extrusion of selected
materials.
TABLE-US-00002 O.D. I.D. Extrusion Extrusion TEST # ALLOY Inches mm
Inches mm Ratio Rate 1 Mg--2Si 0.292 7.42 0.231 5.87 48.977 7.347 2
Mg--7Si 0.291 7.39 0.233 5.92 51.412 7.712 3 AZ31F 0.291 7.39 0.232
5.89 50.637 7.596 4 ZK60-TS 0.293 7.44 0.23 5.84 47.422 7.113
AVERAGE 0.292 7.41 0.232 5.88 49.612 7.442 STD. DEV. 9.5E-4 2.4E-2
1.3E-3 0.033 1.779 0.267
[0051] Extrusion ratio (R) may be calculated from Equation [1], as
follows:
R=A.sub.0/A.sub.f [1]
[0052] Here, (A.sub.0) is the initial cross sectional area of the
billet, and (A.sub.f) is the final cross-sectional area of the
extrusion structures following extrusion.
[0053] In some embodiments, shear-assisted extrusion of the present
invention may be performed continuously to produce extrusion
structures of any selected and/or extended lengths. In some
embodiments, shear-assisted extrusion may be performed
semi-continuously or batch-wise to produce various and/or multiple
extrusion structures.
Microstructure Refinement
[0054] Shear-assisted extrusion processing of the present invention
refines the microstructure of cast billets. For example, billets
containing coarse matrix grains and second-phase intermetallic
particles with sizes up to a millimeter (1000 microns) may be
refined in a single process step. In some embodiments, the process
yields a microstructure containing fine matrix grains and
second-phase intermetallic particles with a size less than or equal
to about 10 microns. In some embodiments, the process yields a
microstructure containing very (ultra) fine matrix grains and
second-phase intermetallic particles with a size less than or equal
to about 1 micron or finer. However, no limitations are intended.
For example, in some embodiments, the present invention alters the
morphology of second-phase particles in the starting billet
material from an aspect ratio above about 2 to an aspect ratio
below about 2 following shear-assisted extrusion processing. In
some embodiments, microstructure grains and particles of the
original billet material are refined by at least a factor of 2
times or finer. Grains and/or particles are formed that have a size
at least one-half that of grains in the original billet material
prior to extrusion processing. Shear-assisted extrusion processing
can further distribute grains and particles uniformly within the
refined microstructure.
[0055] FIG. 7 is a photomicrograph showing refined grains in an
exemplary high-performance extrusion structure following
shear-assisted extrusion. In the figure, grains include a size
below about 10 microns, and more particularly below about 5
microns. In some embodiments, the resulting microstructure may be
amorphous, meaning grain size is approximately zero. Thus, no
limitations are intended.
Applications
[0056] Extrusion structures of the present invention find
application as parts, pieces, or components in various devices. In
some embodiments, tubular extrusion structures of the present
invention may find application as crush tubes or compression
structures in front and rear bumpers of automobiles or in other
compression applications. In other embodiments, extrusion
structures of the present invention may be in the form of
lightweight alloy tubes that find application as dissolvable
stents. For example, tubes may be inexpensively produced and
subsequently machined into stents. In yet other embodiments, hollow
extrusion structures of the present invention may find application
as bendable components, e.g., in pillar applications for use in
automobiles. All applications as will be envisioned by those of
ordinary skill in the art in view of the disclosure are within the
scope of the present invention. No limitations are intended.
[0057] While preferred embodiments of the present invention have
been shown and described, it will be apparent to those of ordinary
skill in the art that many changes and modifications may be made
without departing from the invention in its true scope and broader
aspects. The appended claims are therefore intended to cover all
such changes and modifications as fall within the spirit and scope
of the invention.
* * * * *