U.S. patent application number 15/455432 was filed with the patent office on 2018-03-15 for methods and apparatus for rejuvenation of amorphous alloys and micro-alloying.
The applicant listed for this patent is Apple Inc.. Invention is credited to Naoto Matsuyuki, Yoshihiko Yokoyama.
Application Number | 20180073104 15/455432 |
Document ID | / |
Family ID | 61559202 |
Filed Date | 2018-03-15 |
United States Patent
Application |
20180073104 |
Kind Code |
A1 |
Yokoyama; Yoshihiko ; et
al. |
March 15, 2018 |
METHODS AND APPARATUS FOR REJUVENATION OF AMORPHOUS ALLOYS AND
MICRO-ALLOYING
Abstract
The disclosure provides a method of modifying a surface of a
metallic glass. The method includes applying an electron beam
within an energy band to a crystalline metal portion at a surface
zone of the metallic glass. The method also includes changing the
crystalline metal portion to an amorphous portion at the surface
zone of the metallic glass, while a bulk region embedded in the
metallic glass under the surface zone remains crystalline.
Inventors: |
Yokoyama; Yoshihiko; (Tokyo,
JP) ; Matsuyuki; Naoto; (Kasugai-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
61559202 |
Appl. No.: |
15/455432 |
Filed: |
March 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62394070 |
Sep 13, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 45/008 20130101;
C22C 1/02 20130101; C22C 45/10 20130101; C22C 45/003 20130101 |
International
Class: |
C22C 1/02 20060101
C22C001/02; C22C 45/00 20060101 C22C045/00; C22C 45/10 20060101
C22C045/10 |
Claims
1. A method of modifying a crystalline metal portion in a metallic
glass comprising: applying an electron beam within an energy band
to the crystalline metal portion at a surface zone of the metallic
glass; and changing the crystalline metal portion to an amorphous
portion at the surface zone of the metallic glass, while a bulk
metal region embedded in the metallic glass under the surface zone
remains crystalline.
2. The method of claim 1, wherein the surface zone has a depth up
to 100 .mu.m.
3. The method of claim 1, further comprising selecting the energy
band of the electron beam by filtering out electrons having energy
above an upper threshold energy.
4. The method of claim 3, comprising filtering out the electrons
having energy below a lower threshold energy.
5. The method of claim 1, wherein the electron beam is a pulsed
electron beam.
6. The method of claim 1, wherein the surface zone has the same
chemical composition as the bulk region.
7. The method of claim 1, wherein the metallic glass is selected
from a group consisting of a Zr-based metallic glass, a Pt-based
metallic glass, a Pd-based metallic glass, a Au-based metallic
glass, a Ag-based metallic glass, a Ni-based metallic glass, and a
Fe-based metallic glass.
8. A method of micro-alloying an element on a metallic glass
comprising: placing a target material onto a portion of a surface
of the metallic glass; and alloying the target material with the
metallic glass to form an amorphous surface zone with a depth of up
to 5 .mu.m in the metallic glass.
9. The method of claim 8, wherein the amorphous surface zone has a
different composition from the metallic glass.
10. The method of claim 8, wherein the target material comprises
copper.
11. The method of claim 8, wherein the metallic glass comprises a
Zr-based metallic glass, a Pt-based metallic glass, a Pd-based
metallic glass, a Au-based metallic glass, a Ag-based metallic
glass, a Ni-based metallic glass, and a Fe-based metallic
glass.
12. The method of claim 8, further comprising applying an electron
beam to the surface of the metallic glass, before alloying the
target material.
13. The method of claim 12, wherein the electron beam is a pulsed
electron beam.
14. A method of modifying a surface of a metallic glass comprising:
applying an electron beam to a localized crystalline metal portion
at the surface of the metallic glass to heat the metallic glass at
a temperature below the melting temperature of the metallic glass;
and rejuvenating the localized crystalline metal portion into an
amorphous portion.
15. The method of claim 14, wherein the amorphous portion has a
depth of up to 100 .mu.m.
16. A metal comprising a metallic coating diffused into a surface
of a metallic glass substrate to a depth of at least 50
microns.
17. The metal according to claim 16, wherein the metallic coating
is diffused into the metallic glass substrate to a depth of at
least 75 microns.
18. The metal according to claim 16, wherein the metallic coating
is diffused into the metallic glass substrate to a depth of at
least 90 microns.
19. A metal comprising a metallic coating diffused into a metallic
glass substrate to a depth up to 5 microns.
20. An electronic device comprising a housing, the housing
comprising the metal according to claim 19.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] This patent application claims the benefit of U.S. patent
application Ser. No. 62/394,070, entitled "METHODS AND APPARATUS
FOR REJUVENATION OF AMORPHOUS ALLOYS AND MICRO-ALLOYING," filed on
Sep. 13, 2016 under 35 U.S.C. .sctn. 119(e), which is incorporated
herein by reference in its entirety.
FIELD
[0002] The disclosure is directed to apparatuses and methods for
surface modification by pulsed electron beam radiation.
BACKGROUND
[0003] Amorphous alloys have properties such as high corrosion
resistance, high strength, and large elastic elongation. However,
amorphous alloys are metastable phase materials, which can change
from an amorphous structure towards a thermally stable structure
under certain external factors, such as physical stress. The
transition is a one-way reaction. When the amorphous structure
makes the transition to become the thermally stable structure, such
as a crystalline structure, structural relaxation occurs.
Embrittlement is associated with the structural relaxation.
[0004] In some cases, plastic deformation can localize into a
narrow band region at room temperature, resulting in sudden
fracture, exhibiting almost no macroscopic plastic deformation
under uniaxial tensile and compressive loadings. This brittle
nature can limit the use of amorphous alloys as structural
materials.
SUMMARY
[0005] In an embodiment, a method is provided for surface
modification of a metallic glass. The method includes applying an
electron beam within an energy band to a crystalline metal portion
at the metallic glass surface. The method also includes changing
the crystalline metal portion to an amorphous portion at a surface
zone of the metallic glass surface, while a bulk region embedded in
the metallic glass under the surface zone remains crystalline. The
surface zone may have a depth up to 100 .mu.m. In some variations,
the depth of the surface zone can be greater than 100 .mu.m. The
surface zone may also have the same composition as the bulk
region.
[0006] In an embodiment, a method is provided for micro-alloying an
element on a metallic glass. The method may include sputtering a
target material onto a surface of the metallic glass. The method
may also include alloying the target material with the metallic
glass to form an amorphous surface zone comprising the target
material and the metallic glass. The surface zone may have a depth
of up to 5 .mu.m. The surface zone may also have a different
composition from the metallic glass.
[0007] In an embodiment, a method is provided for surface
modification of a metallic glass. The method may include applying
an electron beam within an energy band to a localized crystalline
metal portion within the surface of the metallic glass. The method
may also include changing the localized crystalline metal portion
at a surface zone of the metallic glass to an amorphous portion
while a bulk region embedded in the metallic glass under the
surface zone remains crystalline. The surface zone may have a depth
of up to 5 .mu.m.
[0008] Additional embodiments and features are set forth in part in
the description that follows, and will become apparent to those
skilled in the art upon examination of the specification or may be
learned by the practice of the disclosed subject matter. A further
understanding of the nature and advantages of the disclosure may be
realized by reference to the remaining portions of the
specification and the drawings, which forms a part of this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The description will be more fully understood with reference
to the following figures and data graphs, which are presented as
various embodiments of the disclosure and should not be construed
as a complete recitation of the scope of the disclosure,
wherein:
[0010] FIG. 1 illustrates a schematic for a conventional apparatus
for pulsed electron beam radiation in accordance with embodiments
of the disclosure.
[0011] FIG. 2 is an optical image that depicts a surface of a
metallic glass including damage by a high intensity electron beam
radiation in accordance with embodiments of the disclosure.
[0012] FIG. 3 illustrates a schematic for a modified apparatus for
pulsed electron beam radiation in accordance with embodiments of
the disclosure.
[0013] FIG. 4 illustrates a schematic configuration of a modified
apparatus for pulsed electron beam radiation including electrically
isolated metallic plates for sputtering and micro-alloying in
accordance with embodiments of the disclosure.
[0014] FIG. 5 shows an optical photo of a modified metallic glass
surface that has a slightly different compositional change due to
micro-alloying from sputtered atoms by the pulsed electron beam
radiation using the modified of FIG. 4 in accordance with
embodiments of the disclosure.
[0015] FIG. 6A illustrates a micro-alloyed surface of Zr-based
metallic glass in an embodiment of the disclosure.
[0016] FIG. 6B illustrates a rejuvenated surface structure on a
crystalline metal portion in a metallic glass in an embodiment of
the disclosure.
[0017] FIG. 7A is a schematic that illustrates an amorphous
structure having a surface melted by an electron beam radiation in
accordance with embodiments of the disclosure.
[0018] FIG. 7B is a schematic that illustrates the surface
modification of the amorphous structure after rejuvenation by the
electron beam in accordance with embodiments of the disclosure.
[0019] FIG. 8 shows X-ray diffraction patterns for a crystalline
metal portion of a metallic glass prior to rejuvenation and an
amorphous portion of the metallic glass after rejuvenation in an
embodiment of the disclosure.
[0020] FIG. 9 is an optical image of a crystalline metal portion in
a metallic glass prior to rejuvenation in an embodiment of the
disclosure.
[0021] FIG. 10 is an optical image of a metallic glass including a
rejuvenated amorphous portion and a crystalline metal portion after
rejuvenation in an embodiment of the disclosure.
[0022] FIG. 11 depicts a portable electronic device having a
metallic glass coating embedded therein.
DETAILED DESCRIPTION
[0023] The disclosure may be understood by reference to the
following detailed description, taken in conjunction with the
drawings as described below. It is noted that, for purposes of
illustrative clarity, certain elements in various drawings may not
be drawn to scale.
[0024] Because metallic glasses may crystallize due to mechanical
stress, or reheating and slowly cooling, the disclosure is directed
to methods of and an apparatus for modifying the surface of the
metallic glass after crystallization. In some embodiments, the
method may include applying an electron beam to a surface of
crystalline metal portion within a metallic glass and rejuvenating
the crystalline surface to become amorphous.
[0025] Rejuvenation is a process that can change a metastable phase
(e.g. crystalline phase or structure) into an amorphous structure
without changing the chemical composition of the metallic glass.
Rejuvenation is accompanied by an increase in the enthalpy and free
volume and is thus the inverse of aging.
[0026] In some embodiments, the method may include rejuvenating a
surface of a metallic glass that has localized regions of
crystalline portion within a metallic glass to become amorphous.
The disclosure also provides a method for micro-alloying at least
one element onto a metallic glass surface. The method may include
sputtering a target material onto the surface of the metallic glass
and micro-alloying the target material with the metallic glass and
forming an amorphous surface region.
[0027] The disclosure also provides a modified pulsed electron beam
radiation apparatus for achieving rejuvenation of a crystalline
metal portion on a metallic glass using pulsed electron beam
radiation. In some embodiments, the modified pulsed electron beam
radiation apparatus includes a pulsed electron beam radiation
apparatus and an energy filter for filtering electrons. The
modified pulsed electron beam radiation apparatus can be used for
surface modification, rework, or repair by healing the surface of
the crystalline metal portion in a metallic glass, which may have
structural relaxation or embrittlement.
[0028] The disclosure also provides a modified pulsed electron beam
radiation apparatus for micro-alloying a surface of a metallic
glass using pulsed electron beam radiation. In some embodiments,
the modified pulsed electron beam radiation apparatus may include a
sputtering capability for scattering a target material toward the
surface of the metallic glass and micro-alloying the target
material with the metallic glass to form an amorphous layer over
the metallic glass.
[0029] FIG. 1 shows a conventional pulsed electron beam apparatus,
which is a pulsed electron beam source or gun. As shown in FIG. 1,
a conventional apparatus 100 includes a cathode 102, an anode 104,
and a high voltage source 106 between the cathode 102 and anode 104
for producing high energy electrons in a vacuum chamber 110. The
vacuum chamber 110 also includes an aperture 112 for outputting an
electron beam. The pulsed electron beam radiation apparatus 100
also includes an electro-lens 108 for focusing an electron beam 114
and outputting the electron beam 114 through the aperture 112.
[0030] The electron beam 114 outputted through the aperture 112 is
in a three-dimensional (3D) cone shape. In the conventional pulsed
electron beam radiation apparatus 100, the electrons have a
relatively broad energy band or energy distribution, i.e. the
electrons have variations in energy. For example, some electrons
may have higher energy than other electrons. The electron beam 114
has an electron energy distribution 122, which is the intensity I
of the electrons versus energy E. As shown in FIG. 1, the electron
energy distribution 122 may look like a bell curve, with a peak
intensity 116 in the middle of the energy distribution, an extra
high energy band 118 near the high energy end (e.g. to the right
side of the peak intensity 116), and a low energy band 120 near the
low energy end (e.g. to the left side of the peak intensity
116).
[0031] One of the drawbacks of the conventional pulsed electron
beam radiation apparatus 100 is that the very high energy of the
electron beam may damage a surface of a metallic glass. In some
cases, the high energy electron beam in the conventional pulsed
electron beam apparatus 100 can create a large hole on the surface
of the metallic glass. FIG. 2 is an image that depicts a surface of
a metallic glass after an accidental attack by high intensity
electron beam radiation, such as from the electrons with energy in
the extra high energy band 118. As shown in FIG. 2, a large hole
202 appears on the surface of a metallic glass 206. Also, a small
hole 204 appears on the surface of the metallic glass 206.
[0032] The modified pulsed electron beam radiation apparatus
disclosed herein can be used to modifying crystalline metal
portions on the surface of the metallic glass. The apparatus can be
used to apply an electron beam to a crystalline metal portion in a
metallic glass surface, and rejuvenating the surface to become
amorphous. In some embodiments, the apparatus can be used to
rejuvenate localized crystalline metal portions to become
amorphous. In other embodiments, the apparatus can be used to form
an amorphous layer on crystalline metal portion in a metallic
glass.
[0033] In some embodiments, the modified pulsed electron beam
radiation includes a filter to reduce the power of the electron
beam radiation. FIG. 3 illustrates a schematic for a modified
apparatus for pulsed electron beam radiation in an embodiment.
Modified pulsed electron beam radiation apparatus 300 includes a
magnet 302 for changing the direction of the electron beam. The
magnet 302 may be formed of a solenoid coil among others.
[0034] As shown in FIG. 3, an electron beam 304 passes through the
aperture 112 of the conventional pulsed electron beam radiation
apparatus 100. The magnet 302 can be used to change the orientation
of the electron beam 304 to bend the electron beam 304 and to
output a beam 306. For example, as illustrated in FIG. 3, the
electron beam 304 impacts the magnet 302 and its orientation is
rotated about 90.degree.. Other orientations are possible, and the
magnet can rotate the electron beam 304 range from 0 to
180.degree..
[0035] Initially, the electron beam 306 has the broad energy
distribution 122 of the conventional pulsed electron beam radiation
apparatus 100. However, the apparatus 300 includes an energy filter
308, such as a bending filter, for modifying the energy
distribution. The energy filter 308 removes both the high energy
electrons and the low energy electrons to output a filtered
electron beam 310, which has a narrower modified energy
distribution 312 than the energy distribution 122. The modified
energy distribution 312 of the modified pulsed electron beam
radiation apparatus 300 has a mean energy 316 and a width 314,
which is smaller than the width 128 of the energy distribution 122
of the electron beam.
[0036] The modified energy distribution 312 of the output electron
beam 310 can be controlled in the modified apparatus 300 by the
filter 308. For example, the mean energy 316 and width 314 of the
modified energy distribution 312 of the electron beam 310 may vary
depending upon applications. In some embodiments, the electrons in
both the extra high energy region 118 and the low energy region 116
are filtered by the filter 308. In some embodiments, the electrons
in the extra high energy region 118 may be filtered out by using
the filter in the modified apparatus 300, while the electrons in
the low energy region 116 may not be filtered.
[0037] In some embodiments, the filter 308 may be a bent type
filter. In alternative embodiments, other filters may be used to
control the energy distribution of the electron beam. The filtered
electron beam 310 may have a varying beam size, which may be
controlled by the filter 308.
[0038] In another embodiment, a target material can be sputtered
onto a specimen by the pulsed electron beam. FIG. 4 illustrates a
schematic configuration of a modified pulsed electron beam
radiation apparatus including electrically isolated metal plates
that contain the target material. The target material is sputtered
from the metal plates, and can be micro-alloyed onto the metallic
glass surface.
[0039] The modified apparatus 400 can be used for sputtering a
target material onto the surface of the metallic glass and
micro-alloying the target material with the metallic glass and
forming an amorphous surface region. Apparatus 400 includes a
pulsed electron beam radiation apparatus 410 as an electron source
and also electrically isolated metal plates 416A-B, which may be
positioned on opposite sides of an electron beam 420 that is
outputted from the pulsed electron beam radiation apparatus 410.
The metal plates 416A-B and the electron beam 420 can all be
contained within a vacuum chamber (not shown). The metal plates 416
may be formed of a target material, such as copper among other
metals. The metal plates 416 must be electrically isolated to keep
the electron beam 420 scattering.
[0040] Sputtering occurs when the side portions 420A and 420B of
the electron beam 420 hit the target materials on both sides of the
electron beam. Sputtering is a process for ejecting atoms from a
solid target material by bombardment of the target by energetic
particles. Sputtering can deposit a layer of the target material
onto the specimen 424, which is placed inside the vacuum chamber
(not shown). The specimen 424 may be a metallic glass.
[0041] When the electron beam 420 hits the metal plates 416, atoms
or ions of the target material are knocked out, referred to as
sputtered atoms. Sputtered atoms or ions may be scattered to the
surface 406 of a metallic glass to form sputtered zones 408A and
408B, respectively, on the surface 406. The middle portion 420C of
the electron beam 420 reaches the inner surface region 404 inside
the sputtered zones or regions 408A and 408B. In the sputtered
regions 408A and 408B, micro-alloying of the target material with
the metallic glass occurs such that the surface composition is
slightly different from the metallic glass.
[0042] In the sputtered zones 408A and 408B, an incoming portion of
the electron beam 420 and the sputtered atoms or ions reach the
surface of the metallic glass 424 simultaneously. As such, the
electron beam 420 causes melting of the metallic glass and
micro-alloying of the sputtered atoms or ions with the metallic
glass 424 in the sputtered zone.
[0043] Also, an electron beam 420 radiating through an aperture 112
of the pulsed electron beam radiation apparatus 410 can be in a
three-dimensional (3D) cone shape. Therefore, the beam size or
diameter 414 near the metal plates 416A-B can be controlled by
varying the distance 412A between the metal plates 416A-B and the
aperture 112. The metal plates include the target material, such as
copper, aluminum, among others.
[0044] The locations of the sputtered regions 408A and 408B can be
controlled by adjusting the distance 418 between two metal plates
416A and 416B and the distance 412B from the surface of the
metallic glass 424.
Methods of Rejuvenating Surfaces of Metallic Glasses using Electron
Beam Radiation
[0045] Crystals on the surface of the metallic glass are not
desirable. The pulsed electron beam radiation can be used for
healing inclusions, e.g. crystals with high melting temperatures.
For example, an electronic case or cover may be formed of a
metallic glass. When crystals appear on the outer surface of an
electronic case, the crystals can detract from the cosmetic appeal
of the electronic case. Also, the inner surface of the electronic
case may need to have a very good control of the geometric
dimensions, such that all the components can fit tightly inside the
electronic case.
[0046] In some embodiments, rejuvenation of a surface of a
localized crystalline portion of a metallic glass by electron beam
radiation may repair the surface of a metallic glass having
localized regions of crystallization. For example, localized
crystalline regions or zones in a metallic glass sample may be
treated with an electron beam to transform localized crystalline
regions into an amorphous structure. For example, an embrittled
sample can be healed by the pulsed electron beam radiation using
the apparatus as shown in FIG. 3. By using electron beam radiation,
a portion of the crystalline metal portion in a metallic glass can
be rejuvenated (i.e. the morphology changed to amorphous).
[0047] The method for surface modification of a metallic glass may
include selecting an energy band for an electron beam from an
electron source. The method may also include applying the electron
beam to a surface of a metallic glass having localized regions of
crystallization and repairing the surface to change the morphology
the localized crystalized regions to become amorphous via the
electron beam radiation. In various aspects, the energy band is
designed to heat the metallic glass to a temperature below the
melting temperature of the metallic glass. The melting temperature
of the metallic glass can depend on the alloy, and can be known for
a particular metallic glass, or can be determined as known to those
skilled in the art.
[0048] In some embodiments, rejuvenation of the surface of the
metallic glass by electron beam radiation may produce a rejuvenated
amorphous region with a depth up to about 100 .mu.m. In some
embodiments, the depth may be less than 90 .mu.m. In some
embodiments, the depth may be less than 80 .mu.m. In some
embodiments, the depth may be less than 70 .mu.m. In some
embodiments, the depth may be less than 60 .mu.m. In some
embodiments, the depth may be less than 50 .mu.m. In some
embodiments, the depth may be less than 40 .mu.m. In some
embodiments, the depth may be less than 30 .mu.m. In some
embodiments, the depth may be less than 20 .mu.m. In some
embodiments, the depth may be greater than 10 .mu.m. In some
embodiments, the depth may be greater than 20 .mu.m. In some
embodiments, the depth may be greater than 30 .mu.m. In some
embodiments, the depth may be greater than 40 .mu.m. In some
embodiments, the depth may be greater than 50 .mu.m. In some
embodiments, the depth may be greater than 60 .mu.m. In some
embodiments, the depth may be greater than 70 .mu.m. In some
embodiments, the depth may be greater than 80 .mu.m. In some
embodiments, the depth may be greater than 90 .mu.m. In some
embodiments, the depth may be greater than 100 .mu.m.
[0049] The method for surface modification of a metallic glass may
include selecting an energy band for an electron beam from an
electron source. The method may also include applying the electron
beam to a surface of a crystalline metal portion in a metallic
glass. The method may further include rejuvenating the surface to
form a surface zone of the crystalized metallic glass, wherein the
surface zone becomes amorphous after the electron beam radiation,
while a bulk region under the surface zone remains crystalline
after the electron beam radiation.
[0050] In other embodiments, the methods and apparatus can be used
to rejuvenate a portion of a crystalline metal portion in a
metallic glass. For example, FIG. 6B illustrates a rejuvenated
metallic glass layer on a crystalline metal portion in a Zr-based
metallic glass in an embodiment. As shown in FIG. 6B, a metallic
glass layer 606 is formed on the crystalline metal portion of a
metallic glass 608 by the pulsed electron beam radiation using the
modified pulsed electron beam radiation apparatus 300. The
rejuvenation is facilitated by controlling the energy of the
electron beam via the electron beam apparatus 300, as described
above. The rejuvenated metallic glass layer 606 is can be about 100
.mu.m thick. In some aspects, the rejuvenated metallic glass layer
is at least 50 .mu.m thick. In some aspects, the rejuvenated
metallic glass layer is at least 150 .mu.m thick. In some aspects,
the rejuvenated metallic glass layer is at least 250 .mu.m thick.
In some aspects, the rejuvenated metallic glass layer is at least
350 .mu.m thick.
[0051] Rejuvenation occurs by electron penetration into the
metallic glass, causing the crystalline metal portion in a metallic
glass to change to an amorphous phase without melting the metallic
glass. This process differs from micro-alloying. The average energy
may vary with the metallic glass and would be low enough in order
not to melt the surface of the metallic glass, but only rejuvenate
the surface of the crystalline metal portion in the metallic glass.
The electron beam of a pulsed electron beam may have an average
energy lower than that used for micro-alloying.
[0052] As demonstrated herein, the electrons may have high enough
energy to melt the surface of the metallic glass and to allow the
metallic glass to micro-alloy with other target elements. FIG. 7A
is a schematic that illustrates an amorphous structure having a
surface melted by an electron beam in an embodiment. As shown in
FIG. 7A, an electron beam 702 radiates toward a surface area 704 of
an amorphous structure or a metallic glass 706. A temperature rise
occurs near the surface area 704 to form a thin temperature rise
region 708, for example, having a thickness of about a few microns,
e.g. 2-3 .mu.m. In the temperature rise region 708, the temperature
may rise to be above the melting temperature of the metallic glass.
Micro-alloying can occur in the melted surface region 708.
[0053] FIG. 7B is a schematic that illustrates the surface
modification or rejuvenation of a crystalline metal portion in a
metallic glass by the electron beam radiation. The surface
temperature rises as a result of the electron beam radiation. A
portion of the electron beam 702 penetrates through the temperature
rise region 708. As such, the penetrated electron beam can change
the atoms of the crystalline metal portion in the metallic glass
706 to become an amorphous phase and to form a rejuvenated
amorphous region 710 from the surface 704. The rejuvenated
amorphous region 710 has a depth of up to 100 .mu.m. The electron
beam radiation modifies the surface region of the crystalline metal
portion in the metallic glass, but does not affect the bulk of the
crystalline metal portion in the metallic glass that extends beyond
the rejuvenated amorphous region 710. A large flux of the electron
beam may be used to enhance the depth of rejuvenated amorphous
region 710. The energy level for the electron beam radiation may be
different from that used for micro-alloying.
[0054] In order to identify the structure of the rejuvenated
surface as shown in FIG. 6B, X-ray diffractometry was used for
analysis. FIG. 8A is an X-ray diffraction pattern for a crystalline
metal portion in a metallic glass prior to rejuvenation in an
embodiment. An X-ray diffraction pattern 800A of the crystalline
metal portion in the metallic glass before the electron beam
radiation includes two major peaks 802, which indicate a
.beta..sub.2 crystalline phase with a composition similar to a
nominal composition.
[0055] FIG. 8B is an X-ray diffraction pattern for a crystalline
metal portion in a metallic glass of FIG. 8A after rejuvenation in
an embodiment. An X-ray diffraction pattern 800B of the metallic
glass after the electron beam radiation includes a broad peak 804,
which indicates an amorphous phase.
[0056] The composition of the rejuvenated surface region remains
unchanged, because no diffusion of elements occurs during the
healing process of a crystalline metal portion in a metallic glass
when healing a crystalline metal portion in a metallic glass by
using an electron beam radiation apparatus 300 having a controlled
energy to form a rejuvenated amorphous structure with a depth of up
to 100 .mu.m. Diffusion refers to a process where two different
material surfaces are in contact, upon the application of
sufficient energy, and atoms from one material move into the other
material through the interface, resulting in an intermediate region
that includes alloys formed by the two materials as a result of the
diffusion.
[0057] FIG. 9 is an optical image of a crystalline metal portion in
a metallic glass prior to rejuvenation by pulsed electron beam
radiation in an embodiment. The metallic glass is crystallized,
including a crystalline metal portion in a metallic glass 904 and a
surface layer 902. It appears that the surface layer 902 has
embrittlement, such that the surface layer 902 includes a
crystalline portion, and appears slightly different from the
metallic glass 904 prior to electron beam radiation.
[0058] FIG. 10 is an optical image of a crystalline metal portion
in a metallic glass after rejuvenation by pulsed electron beam
radiation in an embodiment. As shown in FIG. 10, a surface layer
1002 of a metallic glass substrate 1004 is rejuvenated by the
pulsed electron beam radiation using the apparatus 300 to form a
rejuvenated amorphous structure having a depth of about 60 .mu.m,
which is less than that shown in FIG. 6B. The bulk of the metallic
glass 1004 still remains crystallized, and only the surface region
becomes an amorphous structure without any change in its
composition. Also, as shown in FIG. 10, the amorphous layer 1002 is
homogeneous, which may be better than a partially melted region
from a welding, which causes non-homogeneousness to the
surface.
Methods of Micro-alloying Metallic Glasses using Electron Beam
Radiation
[0059] In other embodiments, the disclosure is directed to methods
of using electron beam radiation to micro-alloy metallic glasses.
The mechanisms for micro-alloying and rejuvenation are different.
Micro-alloying occurs in the surface melt region of the metallic
glass, while rejuvenation occurs by penetrating electrons into the
metallic glass and causing a crystalline metal portion in a
metallic glass to change to an amorphous phase, as explained
above.
[0060] Micro-alloying of metallic glasses can be achieved by
placing a target material, such as Cu, Al, etc., at an intermediate
position between an electron beam gun or source and a specimen, as
shown in FIG. 4. The micro-alloying technique can form an amorphous
surface region with a depth of up to a few microns on the metallic
glass. In some embodiments, the surface zone has a depth of up to
10 .mu.m. In some embodiments, the surface zone has a depth of up
to 5 .mu.m. In some embodiments, the surface zone has a depth of up
to 4 .mu.m. In some embodiments, the surface zone has a depth of up
to 3 .mu.m. In some embodiments, the surface zone has a depth of up
to 2 .mu.m. In some embodiments, the surface zone has a depth of up
to 1 .mu.m. The surface zone has a slightly different composition
from the metallic glass.
[0061] The electron beam is a pulsed electron beam. The average
energy may vary with the metallic glass and would be high enough to
melt the surface of the metallic glass to alloy micro-alloying with
the target material. The electron beam may have an energy band
width sufficient to heat the alloy at or above its melting point.
The melting point of the alloy can readily be determined by those
skilled in the art.
[0062] Generally, the method includes placing a pair of metal
plates between an electron beam source and a surface of a metallic
glass, the metal plates including a target material. The method
also includes sputtering the target material from the metal plates
on the surface of the metallic glass. The method further includes
micro-alloying the target material with the metallic glass and
forming an amorphous surface zone.
[0063] FIG. 5 shows the trial data of copper (Cu) sputtered on a
Zr-based bulk metallic glass (BMG). A ring region 504 is formed on
a metallic glass 502. The ring region 504 is a Cu sputtered region.
The atoms or ions from the target material may be knocked out by
the electron beam radiation to generate sputtered atoms or ions,
which are scattered onto a surface of the metallic glass. The
sputtered atoms or ions can be micro-alloyed with the metallic
glass on the surface by using the pulsed electron beam radiation.
After oxidization, the Cu sputtered region 504 changes color to
become darker. This color change can be caused by micro-alloying of
Cu with the metallic glass.
[0064] The effect of micro-alloying on the metallic glass by pulsed
electron beam radiation was examined. FIG. 6A illustrates a
micro-alloyed surface of a Zr-based metallic glass with Cu in an
embodiment. The micro-alloyed region on the metallic glass may be a
few microns thick. The surface composition can be controlled by
micro-alloying of a target material with the metallic glass by
using the modified pulsed electron beam radiation apparatus 400. As
shown, a copper layer of about 0.5 .mu.m thick was sputtered or
plated on a Zr-based bulk metallic glass. The depth of the melted
region of FIG. 6A may be from about 3 .mu.m to 5 .mu.m. Therefore,
the micro-alloyed region may be about 2 .mu.m thick. In this
micro-alloyed region, the Zr-based metallic glass is micro-alloyed
with Cu. Outside the micro-alloyed region, the Zr-based metallic
glass remains unchanged. The conditions for the pulsed electron
beam include an acceleration voltage, which controls the electron
kinetic energy. Radiation energy can depend upon both density of
electrons and kinetic energy of the electrons. Kinetic energy plays
an important role in affecting the surface modification. The
kinetic energy seems an important factor to control the surface
condition.
[0065] In some embodiments, the acceleration voltage may be at
least 1 kV. In some embodiments, the acceleration voltage may be
greater than 2 kV. In some embodiments, the acceleration voltage
may be greater than 5 kV. In some embodiments, the acceleration
voltage may be greater than 10 kV. In some embodiments, the
acceleration voltage may be greater than 15 kV. In some
embodiments, the acceleration voltage may be greater than 20 kV. In
some embodiments, the acceleration voltage may be greater than 25
kV. In some embodiments, the acceleration voltage may be greater
than 30 kV. In some embodiments, the acceleration voltage may be
less than 35 kV. In some embodiments, the acceleration voltage may
be less than 30 kV. In some embodiments, the acceleration voltage
may be less than 25 kV. In some embodiments, the acceleration
voltage may be less than 20 kV. In some embodiments, the
acceleration voltage may be less than 15 kV. In some embodiments,
the acceleration voltage may be less than 10 kV. In some
embodiments, the acceleration voltage may be less than 5 kV.
[0066] The conditions for the pulsed electron beam may also include
an argon plasma with a pressure of at least 0.01 Pa. In some
embodiments, the pressure may be greater than 0.02 Pa. In some
embodiments, the pressure may be greater than 0.03 Pa. In some
embodiments, the pressure may be greater than 0.04 Pa. In some
embodiments, the pressure may be greater than 0.05 Pa. In some
embodiments, the pressure may be greater than 0.06 Pa. In some
embodiments, the pressure may be greater than 0.07 Pa. In some
embodiments, the pressure may be greater than 0.08 Pa. In some
embodiments, the pressure may be greater than 0.09 Pa. In some
embodiments, the pressure may be greater than 0.10 Pa. In some
embodiments, the pressure may be greater than 0.11 Pa. In some
embodiments, the pressure may be greater than 0.12 Pa. In some
embodiments, the pressure may be greater than 0.13 Pa. In some
embodiments, the pressure may be greater than 0.14 Pa. In some
embodiments, the pressure may be less than 0.15 Pa. In some
embodiments, the pressure may be less than 0.14 Pa. In some
embodiments, the pressure may be less than 0.13 Pa. In some
embodiments, the pressure may be less than 0.12 Pa. In some
embodiments, the pressure may be less than 0.11 Pa. In some
embodiments, the pressure may be less than 0.10 Pa. In some
embodiments, the pressure may be less than 0.09 Pa. In some
embodiments, the pressure may be less than 0.08 Pa. In some
embodiments, the pressure may be less than 0.07 Pa. In some
embodiments, the pressure may be less than 0.06 Pa. In some
embodiments, the pressure may be less than 0.05 Pa. In some
embodiments, the pressure may be less than 0.04 Pa. In some
embodiments, the pressure may be less than 0.03 Pa. In some
embodiments, the pressure may be less than 0.02 Pa.
[0067] The conditions for the pulsed electron beam may also include
a solenoid coil voltage. In some embodiments, the coil voltage may
be greater than 0.1 kV. In some embodiments, the coil voltage may
be greater than 0.2 kV. In some embodiments, the coil voltage may
be greater than 0.3 kV. In some embodiments, the coil voltage may
be greater than 0.4 kV. In some embodiments, the coil voltage may
be greater than 0.5 kV. In some embodiments, the coil voltage may
be greater than 0.6 kV. In some embodiments, the coil voltage may
be greater than 0.7 kV. In some embodiments, the coil voltage may
be greater than 0.8 kV. In some embodiments, the coil voltage may
be greater than 0.9 kV. In some embodiments, the coil voltage may
be greater than 1.0 kV. In some embodiments, the coil voltage may
be greater than 1.1 kV. In some embodiments, the coil voltage may
be greater than 1.2 kV. In some embodiments, the coil voltage may
be greater than 1.3 kV. In some embodiments, the coil voltage may
be greater than 1.4 kV. In some embodiments, the coil voltage may
be greater than 1.5 kV. In some embodiments, the coil voltage may
be greater than 1.6 kV. In some embodiments, the coil voltage may
be greater than 1.7 kV. In some embodiments, the coil voltage may
be greater than 1.8 kV. In some embodiments, the coil voltage may
be greater than 1.9 kV. In some embodiments, the coil voltage may
be less than 2.0 kV. In some embodiments, the coil voltage may be
less than 1.9 kV. In some embodiments, the coil voltage may be less
than 1.8 kV. In some embodiments, the coil voltage may be less than
1.7 kV. In some embodiments, the coil voltage may be less than 1.6
kV. In some embodiments, the coil voltage may be less than 1.5 kV.
In some embodiments, the coil voltage may be less than 1.4 kV. In
some embodiments, the coil voltage may be less than 1.3 kV. In some
embodiments, the coil voltage may be less than 1.2 kV. In some
embodiments, the coil voltage may be less than 1.1 kV. In some
embodiments, the coil voltage may be less than 1.0 kV. In some
embodiments, the coil voltage may be less than 0.9 kV. In some
embodiments, the coil voltage may be less than 0.8 kV. In some
embodiments, the coil voltage may be less than 0.7 kV. In some
embodiments, the coil voltage may be less than 0.6 kV. In some
embodiments, the coil voltage may be less than 0.5 kV. In some
embodiments, the coil voltage may be less than 0.4 kV. In some
embodiments, the coil voltage may be less than 0.3 kV. In some
embodiments, the coil voltage may be less than 0.2 kV.
[0068] In summary, the disclosure provides a pulsed electron beam
radiation apparatus including a filter that can remove the extra
high energy electrons and control the energy of the electron beams.
The pulsed electron beam radiation apparatus can be used for
healing a surface having structural relaxation or embrittlement,
such as a metallic glass that is crystallized.
[0069] In other embodiments, the apparatus can also include adding
a pair of electrically isolated metal plates that are placed
between the pulsed electron beam source and the specimen to be
treated. The metal plates include a target material, which can be
sputtered onto the surface for micro-alloying the surface of the
metallic glass. This micro-alloying technique can be used for
adding an oxide layer on the metallic glass to change the color,
wear resistance, or corrosion resistance, among other
applications.
[0070] In some embodiments, for an as-cast bulk amorphous structure
or bulk metallic glass, the surface of the as-cast bulk amorphous
structure can be treated by the pulsed electron beam radiation to
avoid cracking originating from the surface of the amorphous
structure.
[0071] The systems and methods described herein can be applicable
to any suitable metallic glass known in the art. In some
non-limiting aspects, the metallic glass can be based on, or
alternatively include, one or more elements that oxidize, such as
Zr, Ti, Ta, Hf, Mo, W, and Nb. In some variations, the metallic
glass includes at least about 30% of one or more of Zr, Ti, Ta, Hf,
Mo, W, and Nb. In some variations, the metallic glass includes at
least about 40% of one or more of Zr, Ti, Ta, Hf, Mo, W, and Nb. In
some variations, the metallic glass includes at least about 50% of
one or more of Zr, Ti, Ta, Hf, Mo, W, and Nb. In certain
embodiments, the metallic glass can be based on, or alternatively
include, Zr. In some variations, the metallic glass includes at
least about 30% Zr. In some variations, the metallic glass includes
at least about 40% Zr. In some variations, the metallic glass
includes at least about 50% Zr. Similarly, the surface treated
metallic glass material described herein as a constituent of a
composition or article can be of any type.
[0072] As used herein, the terms including metallic glass, metallic
glass alloy, amorphous metal, amorphous alloy, bulk metallic glass,
and BMG are used interchangeably.
[0073] The metallic glass can include multiple transition metal
elements, such as at least two, at least three, at least four, or
more, transitional metal elements. The metallic glass can also
optionally include one or more nonmetal elements, such as one, at
least two, at least three, at least four, or more, nonmetal
elements. A transition metal element can be any of scandium,
titanium, vanadium, chromium, manganese, iron, cobalt, nickel,
copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium,
ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum,
tungsten, rhenium, osmium, iridium, platinum, gold, mercury,
rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium,
ununnilium, unununium, and ununbium. In one embodiment, a BMG
containing a transition metal element can have at least one of Sc,
Y, La, Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru,
Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, and Hg. Depending
on the application, any suitable transitional metal elements, or
their combinations, can be used.
[0074] Depending on the application, any suitable nonmetal
elements, or their combinations, can be used. A nonmetal element
can be any element that is found in Groups 13-17 in the Periodic
Table. For example, a nonmetal element can be any one of F, CI, Br,
I, At, O, S, Se, Te, Po, N, P, As, Sb, Bi, C, Si, Ge, Sn, Pb, and
B. Occasionally, a nonmetal element can also refer to certain
metalloids (e.g., B, Si, Ge, As, Sb, Te, and Po) in Groups 13-17.
In one embodiment, the nonmetal elements can include B, Si, C, P,
or combinations thereof. Accordingly, for example, the alloy can
include a boride, a carbide, or both.
[0075] In some embodiments, the metallic glass described herein can
be fully alloyed. The term fully alloyed as used herein can account
for minor variations within the error tolerance. For example, it
can refer to at least 90% alloyed, such as at least 95% alloyed,
such as at least 99% alloyed, such as at least 99.5% alloyed, or
such as at least 99.9% alloyed. The percentage herein can refer to
either volume percent or weight percentage, depending on the
context. These percentages can be balanced by impurities, which can
be in terms of composition or phases that are not a part of the
alloy. The alloys can be homogeneous or heterogeneous, e.g., in
composition, distribution of elements, amorphicity/crystallinity,
etc.
[0076] The metallic glass can include any combination of the above
elements in its chemical formula or chemical composition. The
elements can be present at different weight or volume percentages.
Alternatively, in one embodiment, the above-described percentages
can be volume percentages, instead of weight percentages.
[0077] In certain embodiments, the metallic glass can be
zirconium-based. The metallic glass can also be substantially free
of various elements to suit a particular purpose. For example, in
some embodiments, the metallic glass can be substantially free of
nickel, aluminum, titanium, beryllium, or combinations thereof. In
one embodiment, the alloy or the composite is completely free of
nickel, aluminum, titanium, beryllium, or combinations thereof.
[0078] The metallic glasses can further include additional
elements, such as additional transition metal elements, including
Nb, Cr, V, and Co. The additional elements can be present at less
than or equal to about 30 wt %, less than or equal to about 20 wt
%, less than or equal to about 10 wt %, or less than or equal to
about 5 wt %. In one embodiment, the additional, optional element
is at least one of cobalt, manganese, zirconium, tantalum, niobium,
tungsten, yttrium, titanium, vanadium and hafnium to form carbides
and further improve wear and corrosion resistance. Further optional
elements may include phosphorous, germanium and arsenic, totaling
up to about 2%, and preferably less than 1%, to reduce the melting
point. Otherwise incidental impurities should be less than about 2%
and preferably 0.5%.
[0079] In some embodiments, the metallic glass can include a small
amount of impurities. The impurity elements can be intentionally
added to modify the properties of the composition, such as
improving the mechanical properties (e.g., hardness, strength,
fracture mechanism, etc.) and/or improving the corrosion
resistance. Alternatively, the impurities can be present as
inevitable, incidental impurities, such as those obtained as a
byproduct of processing and manufacturing. The impurities can be
less than or equal to about 10 wt %, about 5 wt %, about 2 wt %,
about 1 wt %, about 0.5 wt %, or about 0.1 wt %. In some
embodiments, these percentages can be volume percentages instead of
weight percentages.
[0080] The methods of modifying the surface of a metallic glass,
methods of micro-alloying, and methods of changing crystalline
metal portions in a metallic glass surface can be used in any
metal-containing device known in the art. FIG. 11 depicts a
portable electronic device 1100. The metal substrate that makes up
housing 1102 can be modified as described herein. In various
aspects, the metallic glass can be rejuvenated using lower energy
electron beams. In some aspects, a localized crystalline metal
portion within a metallic glass can be rejuvenated to form an
amorphous structure. Any portion of an electronic device, including
housings, can be formed or altered in any manner as described
herein.
[0081] The methods and apparatus disclosed herein can be valuable
in the fabrication of electronic devices using a metallic
glass-containing part. An electronic device herein can refer to any
electronic device known in the art. For example, it can be a
telephone, such as a mobile phone, and a land-line phone, or any
communication device, such as a smart phone, including, for example
an iPhone.RTM., a watch, for example and AppleWatch.RTM., and an
electronic email sending/receiving device. It can be a part of a
display, such as a digital display, a TV monitor, an
electronic-book reader, a portable web-browser (e.g., iPad.RTM.),
and a computer monitor. It can also be an entertainment device,
including a portable DVD player, conventional DVD player, Blue-Ray
disk player, video game console, music player, such as a portable
music player (e.g., iPod.RTM.), etc. It can also be a part of a
device that provides control, such as controlling the streaming of
images, videos, sounds (e.g., Apple TV.RTM.), or it can be a remote
control for an electronic device. It can be a part of a computer or
its accessories, such as the hard drive tower housing or casing,
laptop housing, laptop keyboard, laptop track pad, desktop
keyboard, mouse, and speaker. The article can also be applied to a
device such as a watch or a clock.
[0082] The methods can also be valuable in forming wearable
metallic glass products that have a good cosmetic profile and do
not readily degrade or show evidence of wear.
[0083] Any ranges cited herein are inclusive. The terms
"substantially" and "about" used throughout this Specification are
used to describe and account for small fluctuations. For example,
they can refer to less than or equal to .+-.5%, such as less than
or equal to .+-.2%, such as less than or equal to .+-.1%, such as
less than or equal to .+-.0.5%, such as less than or equal to
.+-.0.2%, such as less than or equal to .+-.0.1%, such as less than
or equal to .+-.0.05%.
[0084] Having described several embodiments, it will be recognized
by those skilled in the art that various modifications, alternative
constructions, and equivalents may be used without departing from
the spirit of the invention. Additionally, a number of well-known
processes and elements have not been described in order to avoid
unnecessarily obscuring the present invention. Accordingly, the
above description should not be taken as limiting the scope of the
invention.
[0085] Those skilled in the art will appreciate that the presently
disclosed embodiments teach by way of example and not by
limitation. Therefore, the matter contained in the above
description or shown in the accompanying drawings should be
interpreted as illustrative and not in a limiting sense. The
following claims are intended to cover all generic and specific
features described herein, as well as all statements of the scope
of the present method and system, which, as a matter of language,
might be said to fall there between.
* * * * *