U.S. patent application number 15/965266 was filed with the patent office on 2018-11-01 for system and method for forming nano-particles in additively-manufactured metal alloys.
The applicant listed for this patent is Lehigh University, TE Connectivity Corporation. Invention is credited to Martin William Bayes, Wojciech Z. Misiolek, Gregory Thomas Pawlikowski, Anthony P. Ventura.
Application Number | 20180311736 15/965266 |
Document ID | / |
Family ID | 63915522 |
Filed Date | 2018-11-01 |
United States Patent
Application |
20180311736 |
Kind Code |
A1 |
Pawlikowski; Gregory Thomas ;
et al. |
November 1, 2018 |
System and Method for Forming Nano-Particles in
Additively-Manufactured Metal Alloys
Abstract
In some embodiments, a method of producing a metallic article
includes providing a metallic powder, selecting a predetermined
concentration for a reactive component, providing a controlled
atmosphere including the reactive component at the predetermined
concentration, and additively manufacturing the metallic article
from the metallic powder under the controlled atmosphere. The
metallic powder includes a metallic element or metallic alloy. The
reactive component reacts with the metallic powder in a weld pool
formed during the additive manufacturing to form a dispersion of
nano-particles in the weld pool. The nano-particles are dispersed
throughout the metallic article in a substantially uniform manner.
In some embodiments, the metallic powder includes the reactive
component. Metallic articles formed by the disclosed methods are
also disclosed.
Inventors: |
Pawlikowski; Gregory Thomas;
(Windsor, PA) ; Bayes; Martin William; (Hopkinton,
MA) ; Ventura; Anthony P.; (South Glastonbury,
CT) ; Misiolek; Wojciech Z.; (Blue Bell, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TE Connectivity Corporation
Lehigh University |
Berwyn
Bethlehem |
PA
PA |
US
US |
|
|
Family ID: |
63915522 |
Appl. No.: |
15/965266 |
Filed: |
April 27, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62491792 |
Apr 28, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2301/10 20130101;
B22F 1/0022 20130101; B33Y 10/00 20141201; B22F 2003/1057 20130101;
C22C 1/053 20130101; B22F 2201/20 20130101; Y02P 10/25 20151101;
B22F 3/1007 20130101; B22F 2998/10 20130101; C22C 32/0021 20130101;
B22F 3/1055 20130101; B22F 2999/00 20130101; B22F 2999/00 20130101;
B22F 3/1055 20130101; B22F 3/1007 20130101; B22F 2201/03 20130101;
B22F 2201/02 20130101; B22F 2201/30 20130101; B22F 2999/00
20130101; B22F 3/1055 20130101; C22C 1/053 20130101 |
International
Class: |
B22F 3/105 20060101
B22F003/105; B22F 1/00 20060101 B22F001/00 |
Claims
1. A method of producing a metallic article, the method comprising:
providing a metallic powder, wherein the metallic powder comprises
a metallic element or metallic alloy; selecting a predetermined
concentration for a reactive component; providing a controlled
atmosphere comprising the reactive component at the predetermined
concentration; and additively manufacturing the metallic article
from the metallic powder under the controlled atmosphere such that
the reactive component reacts with the metallic powder in a weld
pool formed during the additive manufacturing to form a dispersion
of nano-particles in the weld pool; wherein the nano-particles are
dispersed throughout the metallic article in a substantially
uniform manner.
2. The method of claim 1, wherein the metallic powder is copper or
a copper-based alloy.
3. The method of claim 2, wherein the copper-based alloy is a
copper-nickel-silicon alloy or a copper-tin alloy.
4. The method of claim 1, wherein the controlled atmosphere further
comprises an inert gas.
5. The method of claim 4, wherein the inert gas is selected from
the group consisting of argon, nitrogen, and a combination
thereof.
6. The method of claim 1, wherein the controlled atmosphere is a
vacuum.
7. The method of claim 1, wherein the reactive component comprises
an element selected from the group consisting of oxygen, nitrogen,
silicon, carbon, and a combination thereof.
8. The method of claim 1, wherein the nano-particles are nano-oxide
particles.
9. The method of claim 1 further comprising subjecting the metallic
article to a single-step precipitation hardening process, without
solutionizing the metallic article between the additive
manufacturing and the precipitation hardening, to enhance at least
one mechanical property of the metallic article.
10. The method of claim 1, wherein the additive manufacturing
comprises selective laser melting or electron beam melting.
11. A metallic article formed by the method of claim 1.
12. A method of producing a metallic article, the method
comprising: selecting a predetermined concentration for a reactive
component; providing a metallic powder, wherein the metallic powder
comprises a metallic element or metallic alloy and the reactive
component at the predetermined concentration; providing a
controlled atmosphere; and additively manufacturing the metallic
article from the metallic powder under the controlled atmosphere
such that the reactive component reacts with the metallic powder in
a weld pool formed during the additive manufacturing to form a
dispersion of nano-particles in the weld pool; wherein the
nano-particles are dispersed throughout the metallic article in a
substantially uniform manner.
13. The method of claim 12, wherein the metallic element or
metallic alloy is copper, a copper-based alloy, a
copper-nickel-silicon alloy or a copper-tin alloy.
14. The method of claim 12, wherein the controlled atmosphere is an
inert gas atmosphere.
15. The method of claim 14, wherein the inert gas is selected from
the group consisting of argon, nitrogen, and a combination
thereof.
16. The method of claim 12, wherein the controlled atmosphere is a
vacuum.
17. The method of claim 12, wherein the reactive component
comprises an element selected from the group consisting of oxygen,
nitrogen, silicon, carbon, and a combination thereof.
18. The method of claim 12, wherein the nano-particles are
nano-oxide particles.
19. The method of claim 12 further comprising subjecting the
metallic article to a single-step precipitation hardening process,
without solutionizing the metallic article between the additive
manufacturing and the precipitation hardening, to enhance at least
one mechanical property of the metallic article.
20. The method of claim 12, wherein the additive manufacturing
comprises selective laser melting or electron beam melting.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is an application under 35 USC 111(a) and
claims priority under 35 USC 119 from Provisional Application Ser.
No. 62/491,792, filed Apr. 28, 2017 under 35 USC 111(b). The
disclosure of that provisional application is incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The described invention relates in general to additive
manufacturing processes, and more specifically to a system and
method for forming nano-particles in certain types of metal alloys,
particularly those created by beam melting processes such as
selective laser melting and electron beam melting.
BACKGROUND OF THE INVENTION
[0003] When a cast pure metal or alloy is permanently deformed in
any manner, it is considered a wrought metal. Wrought metals are
mostly base metal alloys, such as stainless steel,
cobalt-chromium-nickel, nickel-titanium, and beta-titanium. Because
of plastic deformation, the microstructure of an alloy is altered
and the alloy exhibits mechanical properties that are different
from those it had in the as-cast state. The most significant
changes are its proportional limit and ductility. Ductility refers
to a solid material stretching under tensile stress. If ductile, a
material may be stretched into a wire or similar structure.
Malleability, a similar mechanical property, is a material's
ability to deform under pressure (compressive stress). If
malleable, a material may be flattened by hammering or rolling.
[0004] Precipitation hardening, also called age hardening, is a
heat treatment technique used to increase the yield strength of
malleable materials, including most structural alloys of aluminum,
magnesium, nickel, titanium, and some steels and stainless steels.
The process of precipitation hardening produces uniformly dispersed
particles (i.e., precipitates) within the grain structure of a
metal that hinder dislocation motion, thereby strengthening the
metal and enhancing its mechanical properties. These precipitates
are generally conventionally formed using a two-step process: (i)
an initial solution heat treatment (i.e. solutionization) at a high
temperature; and (ii) a precipitation hardening treatment at a
lower temperature, which results in the formation of precipitates.
The solution heat treatment results in a single-phase solution, and
the precipitation hardening treatment results in the formation of
precipitates of appropriate size and morphology to enhance certain
mechanical properties of the material. Precipitation hardening is
typically performed in a vacuum having an inert atmosphere at
temperatures ranging from 900.degree. F. to 1150.degree. F.
(480.degree. C. to 620.degree. C.) for steel alloys to below
400.degree. F. (200.degree. C.) for some aluminum alloys. The
process ranges in time from one to twenty-four hours depending on
the specific material and specified characteristics.
Precipitation-hardened alloys may be used for a variety of
applications, including those where prolonged exposure to elevated
temperatures or other harsh environments may occur.
[0005] As an alternative to using wrought alloys for creating
components or parts, selective laser melting (SLM) and electron
beam melting (EBM) are additive manufacturing techniques that
utilize a directed energy to selectively fuse together a
predetermined portion of the surface of a bed of powdered metal
material. SLM uses a laser beam as the directed energy, whereas EBM
uses an electron beam as the directed energy. The directed energy
source is automatically aimed at points in space that are defined
by a series of horizontal layers within a three-dimensional (3D)
model, thereby melting/welding the powdered metal into a solid
structure. SLM and EBM machines are commercially available and
utilize a 3D computer-aided design (CAD) model, where a data file
is created and then sent to the machine's processing unit. A
technician typically manipulates this 3D model to best orient the
geometry for part building and adds one or more support structures
as appropriate. Once this "build file" has been completed, it is
"sliced" into the horizontal layers that the machine builds in and
is downloaded to the machine, allowing the build to commence.
[0006] Both selective laser melting and electron beam melting
operate inside an environmentally-controlled build chamber that
also includes a material dispensing system, a build platform, and a
re-coater blade that is used to move new powder over the build
platform. The environment inside the chamber is conventionally
either an inert gas or a vacuum. Metal powder is fused into a solid
part by melting or welding the powder locally using the directed
energy beam. Parts are built up additively layer by layer,
typically using layers between about 20 to 100 micrometers (0.8 to
3.9 mil) thick. Such beam melting processes permit highly complex
part geometries to be created directly from 3D CAD data, in a fully
automated manner, in a relatively short period of time, and without
any tooling.
[0007] Selective laser melting and electron beam melting are
net-shape processes that produces parts with high accuracy and
detail resolution, good surface quality, and excellent mechanical
properties. These beam melting processes have many benefits over
traditional manufacturing techniques, including the ability to
rapidly produce a unique part without any special tooling being
required. They also provide for more rigorous testing of prototypes
due to the fact that they are useable with most alloys.
Accordingly, functional prototypes can be created from the same
material as production components. Such systems may also be used in
full-scale production in addition to prototyping. Because
components are built additively, i.e., layer by layer, it is
possible to include internal features and passages that could not
be cast or otherwise machined. Beam melting processes are used to
manufacture direct parts for a variety of industries including
aerospace, dental, medical, and other industries that required
small to medium size, highly complex parts.
[0008] Components or parts made using the beam melting processes
may also be precipitation hardened to increase strength and
durability. However, components or parts made by these processes
may possess certain advantageous characteristics compared to the
wrought forms of the same or similar alloys. Accordingly, there is
an ongoing need for understanding and enhancing the systems and
methods used in such processes to enable the creation of materials
having superior performance characteristics.
BRIEF DESCRIPTION OF THE INVENTION
[0009] The following provides a summary of certain exemplary
embodiments of the present invention. This summary is not an
extensive overview and is not intended to identify key or critical
aspects or elements of the present invention or to delineate its
scope.
[0010] In accordance with one aspect of the present invention, a
method of producing a metallic article includes providing a
metallic powder, selecting a predetermined concentration for a
reactive component, providing a controlled atmosphere including the
reactive component at the predetermined concentration, and
additively manufacturing the metallic article from the metallic
powder under the controlled atmosphere. The metallic powder
includes a metallic element or metallic alloy. The reactive
component reacts with the metallic powder in a weld pool formed
during the additive manufacturing to form a dispersion of
nano-particles in the weld pool. The nano-particles are dispersed
throughout the metallic article in a substantially uniform
manner.
[0011] In accordance with another aspect of the present invention,
a method of producing a metallic article includes selecting a
predetermined concentration for a reactive component, providing a
metallic powder, providing a controlled atmosphere, and additively
manufacturing the metallic article from the metallic powder under
the controlled atmosphere. The metallic powder includes a metallic
element or metallic alloy and the reactive component at the
predetermined concentration. The reactive component reacts with the
metallic powder in a weld pool formed during the additive
manufacturing to form a dispersion of nano-particles in the weld
pool. The nano-particles are dispersed throughout the metallic
article in a substantially uniform manner.
[0012] Additional features and aspects of the present invention
will become apparent to those of ordinary skill in the art upon
reading and understanding the following detailed description of the
exemplary embodiments. As will be appreciated by the skilled
artisan, further embodiments of the invention are possible without
departing from the scope and spirit of the invention. Accordingly,
the descriptions are to be regarded as illustrative and not
restrictive in nature.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Exemplary embodiments of the present invention are described
below. Although the following detailed description contains many
specifics for purposes of illustration, a person of ordinary skill
in the art will appreciate that many variations and alterations to
the following details are within the scope of the invention.
Accordingly, the following embodiments of the invention are set
forth without any loss of generality to, and without imposing
limitations upon, the claimed invention.
[0014] The present invention relates generally to additive
manufacturing processes, and more specifically to systems and
methods for forming nano-particles, such as, for example,
nano-oxide particles, in certain types of metal alloys, such as,
for example, copper-based alloys created by additive
manufacturing.
[0015] Additive manufacturing, as used herein, refers to any
three-dimensional (3D) printing process by which a metallic article
is formed using a directed energy source to additively melt and
fuse a metallic powder layer-by-layer to build up the article.
Additive manufacturing processes include, but are not limited to,
selective laser melting (SLM), selective laser sintering (SLS),
direct metal laser sintering (DMLS), direct metal laser melting
(DMLM), and electron beam melting (EBM).
[0016] Selective laser melting, as used herein, refers to any
additive manufacturing process using a laser beam as the directed
energy source. Selective laser melting processes include, but are
not limited to, SLS, DMLS, and DMLM.
[0017] A nano-particle, as used herein, refers to any dispersoid
particle formed in a melt pool during an additive manufacturing
process by reaction between a reactive component and a metal. In
some embodiments, the nano-particle has a size in the range of
about 1 nm to about 100 nm, alternatively in the range of about 1
nm to about 200 nm, alternatively in the range of about 1 nm to
about 1000 nm, or any value, range, or sub-range therebetween,
depending on the conditions under which the nano-particle is
formed.
[0018] A non-reactive gas, as used herein, refers to a gas that
does not react with the melt pool formed by the metallic powder of
a metallic element or alloy during an additive manufacturing
process. As certain gases may react with one metallic element or
alloy but not another, whether a particular gas is non-reactive may
be dependent on the specific metallic element or alloy being used
to additively manufacture an article.
[0019] A reactive component, as used herein, refers to a compound
or element that reacts with the melt pool formed by the metallic
powder of a metallic element or alloy during an additive
manufacturing process. The reactive component may be provided in
the atmosphere of the additive manufacturing device or in the
powder from which the article is additively manufactured.
[0020] One aspect of this invention involves modifying or otherwise
manipulating the composition of the metallic powder and/or the
composition of the gas or gases contained in the atmosphere inside
the printing chamber used in an additive manufacturing system
(referred to as "headspace modulation") to form metal compounds
that confer desired characteristics such as nano-particles. In some
embodiments, the atmosphere includes primarily a non-reactive gas
but also a predetermined level of a reactive component. In some
embodiments, the atmosphere is a reduced pressure atmosphere or
vacuum with a predetermined concentration of a reactive component.
In some embodiments, the powder includes a predetermined
concentration of a reactive component. In some embodiments, the
predetermined concentration of the reactive component is selected
to produce an article having specific mechanical properties or a
specific concentration of nano-particles.
[0021] The metallic powder may have any composition that reacts
with a reactive component. In some embodiments, the metallic powder
is a pure metallic element. In some embodiments, the metallic
powder is a metallic alloy. In some embodiments, the metallic
powder is pure copper, a copper-based alloy, a copper-tin alloy, or
a copper-nickel-silicon alloy. In some embodiments, the metallic
powder is an iron-based alloy or a steel alloy. In some
embodiments, the metallic powder is not a steel alloy. In some
embodiments, the metallic powder is not an iron-based alloy.
[0022] In some embodiments, the reactive component is oxygen. The
unique effect from the additive manufacturing process, however, may
not be limited to the use of oxygen as the reactive component to
form of nano-oxide particles, but may be extended to other metal
compounds that may be formed in the presence of suitable gases
within the chamber gases, such as nitrides (through the presence of
small quantities of nitrogen in a vacuum or an argon atmosphere) or
silicides/carbides (through the presence of volatile silicon or
carbon compounds in a vacuum or in a nitrogen or an argon
atmosphere). In some embodiments, the reactive component is not
oxygen but instead is a reactive component other than oxygen.
Changing the relative concentrations and/or the composition of the
purge gases surrounding the printing parts would presumably control
the type and quantity of other metal compounds within the printed
parts, thereby yielding desired improvements in mechanical
properties.
[0023] The melt pool formed during the additive manufacturing
process is understood to be very dynamic, with significant flow
occurring within the melt pool leading to significant mixing,
stirring, and entraining. This movement permits an increased level
of incorporation of a reactive component from the atmosphere into
the melt pool and also an increased rate of reaction between the
reactive component and the metallic element or alloy to form the
nano-particles. In some embodiments, the amount of formed
dispersoids from the additive manufacturing and precipitates from
the precipitation hardening is greater than what is possible by
solutionizing and precipitation hardening for the same metallic
element/alloy. The rapid cooling which occurs upon removal of the
directed heat source essentially then leads to freezing of the
nano-particles in place and a relatively homogeneous distribution
of the nano-particles in the additively-manufactured article.
[0024] The rapid cooling of the melt pool in the additive
manufacturing process provides homogeneity in the formed article
similar to a first solutionizing step of a conventional
precipitation hardening process of a wrought material. With regard
to certain copper/nickel/silicon (CuNiSi) alloys, the
micro-precipitation of a Ni--Si compound improves the mechanical
properties, and the additional formation of the nano-oxide
particles further enhances the mechanical properties. These
enhanced mechanical properties are maintained over an extended
exposure of the alloy to elevated temperatures that would normally
have resulted in a decrease in such mechanical properties for a
wrought form of the same alloy. Accordingly, precipitation
hardening from nano-particles formed during an additive
manufacturing process may be utilized to create Cu-based structures
that maintain their mechanical properties for longer time periods
at elevated temperatures. Such materials are beneficial for
electrical connector applications in harsh environments, where
extreme temperatures typically degrade the performance of
conventional copper-based contacts, or for other applications that
require copper-based parts that maintain their structural integrity
and electrical characteristics for prolonged periods of time.
[0025] As previously discussed, the precipitation of fine
inclusions (precipitation hardening) is a mechanism for
modification of the mechanical properties of metal/metal alloys. In
the processing of metals, the approach typically used to create a
particular material is to form a melt with a desired composition,
solidify that material, and then apply a variety of
post-solidification heat treatments to the material. However, the
compositions attainable (and consequently the types of precipitated
inclusions that are possible) are generally limited to those that
form melts.
[0026] The precipitation hardening process confers greater hardness
to the article subjected to the process. Heat aging processes
increase the mechanical properties of metals up to a maximum before
experiencing a loss of the enhanced mechanical properties as the
exposure of the materials to elevated temperatures continues. The
systems and methods of the present invention provide
additively-manufactured metals and alloys that may be precipitation
hardened in a simpler and more efficient manner than the wrought
versions of these alloys and that may retain the beneficial aspects
of precipitation hardening for a longer period of time or at higher
temperatures due to the presence of nano-particles in the
materials, either as additively-manufactured or after precipitation
hardening.
[0027] Copper-based alloys made by an SLM process have been
observed to include dispersoids in the form of nano-particles, more
specifically nano-oxide particles, and such alloys possess certain
advantageous characteristics compared to the wrought forms of the
same or similar alloys. In addition, the very rapid cooling of
materials formed by additive manufacturing simplifies the process
of precipitation hardening of such materials by making the solution
treatment step (i.e., the first step in the process) unnecessary.
Accordingly, the present invention includes methods for modifying
or manipulating the additive manufacturing process to affect the
formation of advantageous dispersoids.
[0028] In some embodiments, the enhanced mechanical properties of
the article include a tensile strength, more specifically an
ultimate tensile strength, that is better maintained at an elevated
temperature over an extended period of time. This enhanced
mechanical property provides at least two potential advantages.
First, it makes the article easier to process than a wrought
article, because the length of time for the precipitation hardening
is less critical for achieving a predetermine tensile strength or
ultimate tensile strength. Second, it permits use of the article
for a longer period of time without risk of failure in a
high-temperature application compare to a wrought article. In some
embodiments, the enhanced mechanical properties include an enhanced
tensile strength, more specifically an enhanced ultimate tensile
strength. In some embodiments, the enhanced mechanical properties
include an enhanced tensile strength, more specifically an enhanced
ultimate tensile strength, that is better maintained at an elevated
temperature over an extended period of time.
EXAMPLES
[0029] An article was formed by an additive manufacturing process,
more specifically an SLM process of DMLS/DMLM, from a powder of a
copper-tin (Cu--Sn) Cu-4% Sn alloy (95.5-96.5 wt % copper and
3.5-4.5 wt % tin; bronze). In analyzing the structural
characteristics of the article, the nano-oxide particles of the
additively-manufactured alloy were observed to be very stable at an
annealing temperature of 600.degree. C. (1100.degree. F.).
Dispersed nano-oxide particles were identified within the bulk of
the SLM-formed Cu-4% Sn alloy.
[0030] With regard to the Cu-4% Sn alloy, the observed nano-oxide
particles are assumed to have been continuously created during the
SLM process and were observed to be dispersed throughout the bulk
interior of the copper alloy. The nano-oxide particles may be
formed either as a result of the molten metal pool scavenging
residual oxygen present in the otherwise inert (nitrogen)
atmosphere within the deposition chamber or from traces of oxides
in the metallic powders used in the SLM process.
[0031] An article was formed by an additive manufacturing process,
more specifically an optimized SLM process of DMLS/DMLM, from a
powder of a commercial Corson alloy based on CuNiSi, referred to as
70250, having a composition of 2.2-4.2 wt % Ni, 0.25-1.2 wt % Si,
0.05-0.30 wt % magnesium (Mg), up to 0.20 wt % iron (Fe), up to 1.0
wt % zinc (Zn), up to 0.1 wt % manganese (Mn), up to 0.05 wt % lead
(Pb), and a balance of Cu. The article was then subjected to a
precipitation hardening process to maximize its physical and
mechanical properties. The nano-particles in the article after the
precipitation hardening were observed to be substantially spherical
with an average diameter of about 33 nm and to be present at a
concentration of about 0.25 vol % of the article. Similar to other
copper-based alloys, Corson alloys (i.e., alloys that derive their
enhanced mechanical properties from a precipitation process carried
out at elevated temperatures) demonstrate decreased mechanical
properties under longer aging times at elevated temperatures as a
result of a strengthening precipitate coarsening process. In a
separable electrical contact that depends on a spring force to
maintain good conductivity, the loss of mechanical properties may
result in a decreased normal force on the separable interface and a
degradation of the electrical performance across the separable
interface.
[0032] The precipitation hardening process followed the additive
manufacturing of the CuNiSi-based article without a solutionizing
step between the additive manufacturing and the precipitation
hardening. The precipitation hardening process was thus simplified
because an initial solutionizing step was not required.
[0033] In this embodiment, the Corson alloy based on CuNiSi (70250)
alloy powder was created using an optimized SLM process for
printing high density parts and components. This process, which
optimized laser power, laser travel speed, beam focus, spacing
between laser lines, beam offsets, and width of laser raster scan,
was developed to: (i) obtain a relatively smooth and defect free
finish on external surfaces; (ii) attain interior sections with a
density of 98%-100% relative to the reported density of the wrought
form of the alloy; and (iii) create strong and continuous support
structures that sufficiently bond to steel build plates as well as
to the initial layers or printed parts. The laser parameters for a
commercially available bronze alloy were found to be inadequate to
process the CuNiSi alloy. Accordingly, the laser energy
(power/laser scan speed) was increased and a more focused beam
setting was applied.
[0034] Another aspect of this invention involves the formation of
nano-particles, specifically nano-oxide particles, in
additively-manufactured CuNiSi alloys. Precipitation-hardened
CuNiSi materials normally experience a decrease in mechanical
properties when exposed to elevated temperatures for extended
times. As discussed above, nano-oxide particles were identified
within the bulk of both a Cu-4% Sn alloy (bronze) and a CuNiSi
alloy, and are believed to be responsible for an observed reduced
rate of microstructural grain coarsening at 600.degree. C.
(1100.degree. F.). These nano-oxide particles are presumably
created during the additive manufacturing process, which disperses
the particles throughout the bulk of the interior of the material.
The nano-oxide particles may originate from trace oxide on the
surface of the metallic powder used in the DMLS printing process or
may be created during the additive manufacturing process by the
molten metal scavenging trace oxygen from the otherwise inert
atmosphere within the internal environment of an additive
manufacturing machine/system. In either case, the oxide particles
are dispersed throughout the bulk interior of the printed material.
Laboratory observations suggest that a similar phenomenon occurs in
a CuNiSi alloy and may be responsible for enhancing the mechanical
properties during an over-aging condition when fabricated using
DMLS. The unique effect from the additive manufacturing process may
not be limited to Cu/Sn alloys, but are expected to extend to other
copper-based alloys, and even other metal/metal alloy systems. The
unique effect(s) of the observed nano-particles are not expected to
be limited to oxide containing particles, but to extend to other
reactive complexes with metals.
[0035] Although only certain specific reactive components and
metallic elements and alloys are described herein, the methods
described herein may be applied to any pair of a reactive component
and a metallic element or alloy to produce nano-particles in an
additively manufactured article. As such, the metallic element or
alloy may be any composition capable of reacting with a reactive
component when in a melted state to form a nano-particle dispersoid
in a melt pool of the metallic element or alloy. In some
embodiments, the additively-manufactured article has a composition
that is not capable of being precipitation hardened after being
formed. In some embodiments, the additively-manufactured article is
subsequently subjected to a precipitation hardening process, as
described herein.
[0036] While the present invention has been illustrated by the
description of exemplary embodiments thereof, and while the
embodiments have been described in certain detail, it is not the
intention to restrict or in any way limit the scope of the appended
claims to such detail. Additional advantages and modifications will
readily appear to those skilled in the art. Therefore, the
invention in its broader aspects is not limited to any of the
specific details, representative devices and methods, and/or
illustrative examples shown and described. Accordingly, departures
may be made from such details without departing from the spirit or
scope of the general inventive concept.
* * * * *