U.S. patent application number 13/554896 was filed with the patent office on 2013-07-25 for particulate aluminium matrix nano-composites and a process for producing the same.
This patent application is currently assigned to Aditya Birla Science and Technology Company Limited. The applicant listed for this patent is Giri Anirban, Srivastava Vivek. Invention is credited to Giri Anirban, Srivastava Vivek.
Application Number | 20130189151 13/554896 |
Document ID | / |
Family ID | 44307343 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130189151 |
Kind Code |
A1 |
Vivek; Srivastava ; et
al. |
July 25, 2013 |
PARTICULATE ALUMINIUM MATRIX NANO-COMPOSITES AND A PROCESS FOR
PRODUCING THE SAME
Abstract
The present invention provides a process for reinforced aluminum
matrix composite. The aluminum matrix composite is reinforced with
compound selected from the group consisting of Titanium carbide,
Titanium boride, Vanadium and Zirconium compounds. The process is
carried out pneumatically using pressurized carrier gas. The
pressurized carrier gas also provides efficient stirring during the
process which leads to uniform dispersion of the particulate in the
aluminum matrix.
Inventors: |
Vivek; Srivastava; (Lucknow,
IN) ; Anirban; Giri; (Kolkata, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vivek; Srivastava
Anirban; Giri |
Lucknow
Kolkata |
|
IN
IN |
|
|
Assignee: |
Aditya Birla Science and Technology
Company Limited
Mumbai
IN
|
Family ID: |
44307343 |
Appl. No.: |
13/554896 |
Filed: |
July 20, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/IN2011/000043 |
Jan 20, 2011 |
|
|
|
13554896 |
|
|
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|
Current U.S.
Class: |
420/542 ;
164/57.1; 420/528 |
Current CPC
Class: |
C22C 1/1068 20130101;
C22C 21/00 20130101; C22C 1/1036 20130101; C22C 32/0052 20130101;
C22C 32/0073 20130101; C22C 21/08 20130101; C22C 32/0036 20130101;
B22D 25/00 20130101 |
Class at
Publication: |
420/542 ;
164/57.1; 420/528 |
International
Class: |
C22C 21/08 20060101
C22C021/08; B22D 25/00 20060101 B22D025/00; C22C 21/00 20060101
C22C021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2010 |
IN |
168/MUM/2010 |
Claims
1. A process for preparing particulate aluminum matrix
nano-composites, said process comprising the following steps: a.
injecting a mixture comprising (i) at least one metal bearing
compound selected from the group consisting of titanium compounds,
vanadium compounds and zirconium compounds, and (ii) at least one
non-metal bearing compound selected from the group containing
carbon bearing compounds, boron bearing compounds and oxygen
bearing compounds, into molten aluminum metal maintained at a
temperature in the range of 7500 C to 12000 C to obtain a melt; b.
agitating the melt for a period of 5 to 60 minutes to obtain molten
alloy; and c. casting and solidifying the molten alloy.
2. The process as claimed in claim 1, wherein the injecting step is
carried out such that at least one of the compounds in the mixture
is injected pneumatically.
3. The process as claimed in claim 1, wherein the injecting step is
carried out pneumatically using pressurized carrier gas.
4. The process as claimed in claim 1, wherein at least one of the
compounds in the mixture in step a) is pneumatically injected into
the molten aluminum through a feeder attached to a submersible
lance, said lance being immersed in the molten aluminum metal.
5. The process as claimed in claim 1, wherein the melt is agitated
with a carrier gas.
6. The process as claimed in claim 1, wherein the melt is agitated
with the carrier gas over a period of 5 to 60 minutes.
7. The process as claimed in claim 1, wherein the carrier gas is
selected from the group consisting of argon and nitrogen.
8. The process as claimed in claim 1, wherein the compound in step
a) is selected from the group consisting of potassium titanium
fluoride, titanium oxide, titanium diboride, silica, alumina, zinc
oxide and cuprous oxide.
9. The process as claimed in claim 1, wherein the compound in step
a) is a titanium compound selected from the group consisting of
potassium titanium fluoride and titanium oxide.
10. The process as claimed in claim 1, wherein the metal bearing
compound is in powder form.
11. The process as claimed in claim 1, wherein the non metal
bearing compound is selected from carbon bearing compounds and is
further selected from the group consisting of graphite powder,
carbon-dioxide and methane gas.
12. The process as claimed in claim 1, wherein the metal bearing
compound selected is a compound of titanium and the non metal
bearing compound is selected from carbon bearing compounds and the
particulate aluminum matrix nano-composite so formed contains up to
15% titanium carbide composite.
13. The process as claimed in claim 1, wherein the particulate
aluminum matrix nano-composite further comprises at least one
alloying metal selected from the group consisting of magnesium,
copper, zinc and silicon.
14. An aluminum matrix nano-composite as prepared by the process
claimed in claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of
International Patent Application No. PCT/IN2011/000043 filed on
Jan. 20, 2011. Accordingly, this application claims benefit of
International Patent Application No. PCT/IN2011/000043 under 35
U.S.C. .sctn.120. Thus, International Patent Application No.
PCT/IN2011/000043 is hereby incorporated by reference in its
entirety.
[0002] International Patent Application No. PCT/IN2011/000043
claims priority to Indian Patent Application No. 168/MUM/2010 filed
on Jan. 21, 2010. Accordingly, this application claims priority to
Indian Patent Application No. 168/MUM/2010 under 35 U.S.C.
.sctn.119(a). Accordingly, Indian Patent Application No.
168/MUM/2010 is hereby incorporated by reference in its
entirety.
FIELD OF INVENTION
[0003] The present disclosure relates to metal matrix
composites.
[0004] Particularly, the present disclosure envisages a reinforced
Aluminum composites and a process for producing the same.
DEFINITION OF THE TERM USED IN THE SPECIFICATION
[0005] The term "Pneumatically" used in the specification means a
process (function/operation) carried out using air, gas such as a
carrier/inert gas or a gaseous mixture.
BACKGROUND OF INVENTION
[0006] A metal matrix composite (MMC) is a composite material with
at least two constituent parts, one being a metal and the other
material being a different non metallic material such as a ceramic
or inorganic compound.
[0007] Metal matrix composites (MMC) are tailor made material
comprising a reinforcing material dispersed in a metal matrix. The
reinforcing material can be synthesized externally and added to the
metal matrix or else prepared in-situ in the metal.
[0008] One particular class of MMC that have gained more interest
in the recent times is particulate reinforced aluminum matrix
composites, prepared by in-situ techniques. These composites have
superior mechanical properties compared to the aluminum matrix and
have applications in transportation, electronics and recreational
products.
[0009] U.S. Pat. No. 4,772,452, discloses a process for TiC
reinforced aluminum matrix composites wherein the aluminum metal,
titanium bearing compound and the carbide, all provided in the
powder form are pre-mixed, compacted and further heated at a
reaction temperature approximating melting point of the aluminum to
produce the composite.
[0010] U.S. Pat. No. 6,843,865, discloses a process for TiC
reinforced aluminum matrix composites wherein the mixture of
aluminum and titanium metals in its molten form is reacted with a
halide of carbon to produce the composite. The reaction is carried
out under vigorous mechanical stirring.
[0011] U.S. Pat. No. 4,748,001 discloses a process for TiC
reinforced aluminum matrix composites wherein the carbon powder
preheated to 7000 C is added to the molten mixture of aluminum and
titanium metals and the melt is stirred vigorously at high
temperature and additional processing is carried out at a very high
temperature (1100 to 1400.degree. C.) to produce the desired
composite. The melt is agitated by mechanical stirring.
[0012] One severe limitation of the above techniques is
heterogeneous distribution of the reinforced particulate, leading
to variation in the properties within the sample and batch to
batch. Also other parameters such as additional processing at a
very high temperature (1100 to 1400.degree. C.), preheating of
precursors to allow wetting of the powders to the melt and
controlled powder size within tight specifications to enable good
mixing and wetting leads to high processing cost. Some of the
process as disclosed above are used to make composites with up to
5% particulate reinforcement, beyond which the mixing is very
poor.
[0013] Therefore, there is felt a need to develop a composite
having higher amount of particulate reinforcement and uniform
homogenous distribution of the particulate reinforcement for
superior mechanical properties.
OBJECTS
[0014] Main object of the present disclosure is to prepare aluminum
composites with fine and uniform distribution of the
particulate.
[0015] Another object of the present disclosure is to provide
aluminum composites with improved mechanical properties.
[0016] Yet another object of the disclosure is to provide a cost
effective process for preparing aluminum composites.
SUMMARY OF INVENTION
[0017] A process for preparing particulate aluminum matrix
nano-composites, said process comprising the following steps:
[0018] a) injecting a mixture comprising (i) at least one metal
bearing compound selected from the group consisting of titanium
compounds, vanadium compounds and zirconium compounds, and (ii) at
least one non-metal bearing compound selected from the group
containing carbon bearing compounds, boron bearing compounds and
oxygen bearing compounds into molten aluminum metal maintained at a
temperature in the range of 7500 C to 12000 C to obtain a melt;
[0019] c) agitating the melt for a period of 5 to 60 minutes to
obtain molten composite; and [0020] d) casting and solidifying the
molten composite.
[0021] In a preferred embodiment of the present disclosure the
injecting step is carried out such that at least one of the
compounds in the mixture is injected pneumatically. Typically, the
injecting step is carried out pneumatically using pressurized
carrier gas.
[0022] Typically, at least one of the compounds in the mixture in
step a) is pneumatically injected into the molten aluminum through
a feeder attached to a submersible lance, said lance being immersed
in the molten aluminum metal.
[0023] In a preferred embodiment of the present disclosure the melt
is agitated with a carrier gas. Typically, the melt is agitated
with the carrier gas over a period of 5 to 20 minutes.
[0024] Typically, the carrier gas is selected from the group
consisting of argon and nitrogen.
[0025] Typically, the temperature in the step a) to step b) is
maintained in the range of 8500 C to 10000 C.
[0026] In preferred embodiment of the present disclosure the
compound in step a) is selected from the group consisting of
potassium titanium fluoride, titanium oxide, titanium diboride.
[0027] Typically, the compound is titanium compound selected from
the group consisting of potassium titanium fluoride and titanium
oxide. Typically, the titanium compound is in the powder form.
[0028] In a preferred embodiment of the present disclosure, the
carbon is selected form the group consisting of graphite powder,
carbon-dioxide and methane gas.
[0029] In a preferred embodiment of the present disclosure, the
oxygen is selected from the group consisting of oxygen gas, silica,
alumina, zinc oxide and cuprous oxide.
[0030] In a preferred embodiment of the present disclosure, the
particulate aluminum matrix nano-composite as formed contains up to
15% titanium carbide composite.
[0031] In another aspect of the present disclosure, the particulate
aluminum matrix nano-composite further comprises at least one
alloying metal selected from the group consisting of magnesium,
copper, zinc and silicon.
BRIEF DESCRIPTION OF DRAWINGS
[0032] FIG. 1 represents XRD overlay of samples prepared according
to present disclosure and the conventional route.
[0033] FIG. 2 represents Scanning electron micrographs of prepared
according to present disclosure and the conventional route.
[0034] FIG. 3 represents Tensile curve of cast aluminum sample and
composite made by present disclosure
[0035] FIG. 4 represents Photographs of samples produced by (a)
method of present disclosure and (b) conventional stir casting
method.
[0036] FIG. 5 represents Optical micrograph of sample prepared by
method of present disclosure employing carbon dioxide as source of
carbon.
[0037] FIG. 6 represents Aging curve for composite sample prepared
by method of this disclosure.
[0038] FIG. 7 represents Extruded composite samples.
[0039] FIG. 8 represents Forged composite samples.
DETAILED DESCRIPTION
[0040] Metal matrix composites (MMC) are tailor made material
consisting a reinforcing material dispersed in a metal matrix. The
matrix is a monolithic material into which the reinforcement is
embedded. The reinforcement is provided to improve physical
properties such as wear resistance, friction coefficient, or
thermal conductivity of the metal.
[0041] Various methods are used to prepare MMC such as i) Solid
state method, where powdered metal and reinforcement material are
mixed and then bonded through a process of compaction, degassing,
and thermo-mechanical treatment. ii) Liquid state method wherein
reinforcement material is stirred into the molten metal and allowed
to solidify. iii) A chemical reaction between the reactants to form
reinforcement material in-situ in metal matrix. iv) Vapor
deposition wherein the fiber is passed through a thick cloud of
vaporized metal, coating it.
[0042] Aluminum Matrix Composites are manufactured by the
fabrication methods such as Powder metallurgy (sintering), Stir
casting and Infiltration. Usually the reinforcement of Aluminum
Matrix Composites results in high strength, high stiffness (modulus
of elasticity), Low density, High thermal conductivity and
excellent abrasion resistance of the reinforced metal compared to
properties of pure metal.
[0043] Aluminum Matrix Composites (AMC) are used for manufacturing
automotive parts (pistons, pushrods, brake components), brake
rotors for high speed trains, bicycles, golf clubs, electronic
substrates, cars for high voltage electrical cables.
[0044] The present disclosure provides a process for in-situ
reinforced aluminum matrix composite. The aluminum matrix composite
is reinforced with at least one compound obtained by the reaction
of a metal bearing compound selected from the group consisting of
Titanium compounds, Vanadium compounds, Zirconium compounds, and a
non-metal bearing compound selected from the group consisting of
carbon bearing compounds, boron bearing compounds and oxygen
bearing compounds, wherein the preferred reinforcing compound is
Titanium carbide. TiC particulate is prepared in-situ by injecting
titanium bearing compound and a carbon bearing compound into the
molten aluminum. The Titanium compound is selected from the group
consisting of Potassium titanium fluoride, titanium boride and
titanium oxide. A pressurized powder injection lance is used to
inject the ingredients in the molten aluminum metal. The Titanium
bearing compound (e.g. Potassium titanium fluoride, titanium oxide)
in powder form is injected pneumatically into the molten aluminum
through a submerged lance placed in the bottom of the bath. Carbon
can be added either as graphite powder mixed with titanium bearing
salt or in the form of CO2/methane gas. An inert or reactive gas
acts as the powder carrier and disperses the powder within the
melt. The gas also agitates the melt to ensure intimate mixing,
which enhances the reaction kinetics and lowers the processing
temperature (750-12000 C) and time (5 to 60 min) The process thus
avoids mechanical stirring which may lead to irregular particulate
size Improvement is also observed in the homogeneity of mechanical
properties, e.g. hardness variation is <5% within the casting.
The present disclosure allows higher amount of reinforcement to be
introduced in the melt (up to 15%), without compromising casting
integrity. Composites prepared by this process have a finer and
more uniform distribution compared to those prepared by
conventional route of mechanical stirring. Therefore for the same
volume fraction of particles, composites according to the
disclosure have superior mechanical properties.
[0045] The disclosure will now be described with respect to the
following examples which do not limit the disclosure in any way and
only exemplifies the disclosure.
Example 1
[0046] 462 gms of aluminum metal was melt in a graphite crucible at
900.degree. C. A mixture of Potassium titanium fluoride and carbon
powder (97.3 g of K2TiF6 and 7.5 g of C) was added to the molten
aluminum using a screw feeder attached to an alumina lance immersed
in the molten melt using argon as the carrier gas. After feeding
the additives for 8 minutes, the screw feeder was switched off and
the melt was mixed with argon stirring for additional 5 minutes.
The amount of addition corresponds to a nominal addition of 5% TiC
by volume. At the end of stirring, the crucible was removed from
the furnace, the dross was skimmed off from the melt. Composite
sample, generally represented by numeral 101 was cast in cast iron
moulds.
[0047] FIG. 1 shows the X-ray diffraction pattern of the composite
with peaks corresponding to aluminum, TiC and minor Al3Ti
phases.
[0048] FIG. 2a shows Scanning Electron Microscope analysis showing
a very fine and uniform distribution of equi-axed particles of
Al4C3 and TiC. A few plates of Al3Ti are also found to be
present.
[0049] To compare the homogeneity of the casting produced by the
present disclosure and the convention method, samples prepared by
stir casting (mechanical stirring), generally represented by
numeral 102 and Sample prepared by method of present disclosure,
101 were produced under identical conditions i.e. 9000 C and 30
minutes reaction time. About 15 hardness readings were taken on the
longitudinal section of the casting and analyzed statistically. For
the casting made using submerged lance and argon carrier gas in
accordance with the present disclosure, Vicker's hardness was
measured to be 60.5+/-1.1, while for the casting made using
graphite stirrer the hardness was 65.1+/-1.7. This shows that that
casting made from the present disclosure leads to more homogenous
casting compared to stir casting method
Example 2
[0050] A number of casting were made by the two different methods
as described in example 1 under different process parameters as
tabulated in Table 1. XRD analysis of the composites shows that the
present disclosure allows composites with large volume fraction of
TiC precipitates to be prepared at lower temperatures, in shorter
cycle times and without the need for pre-heating the precursor
material. The presence of TiC precipitates lead to enhancement of
yield strength, tensile strength and Young's modulus as shown in
FIG. 3. Due to the equiaxed and well distributed nature of TiC
precipitates, the ductility of the composites is not
sacrificed.
Example 3
[0051] Metal matrix composites were made as described in example 1.
One
[0052] Sample was prepared using coarse K2TiF6 powder having d90 of
300 micron while another sample was prepared using ground and
sieved K2TiF6 powder having d90 of 68 micron. Hardness of both the
samples was measured to be 51 Hv.
Example 4
[0053] Composite sample, generally represented by numeral 103 was
prepared by the method of the present disclosure as described in
Example 1. 12 kg of aluminum was melt to 9000 C and to the molten
aluminum, a mixture of K2TiF6 and carbon powder was added through a
screw feeder using argon as the carrier gas. The total addition
corresponds to nominal addition of 10% of TiC volume fraction. The
total batch time for the reaction was 20 minutes. After completion
of the reaction, dross was removed from the crucible and skimmed
melt was poured into a sand mould to produce billets. FIG. 4a shows
the photograph of the defect free cast billet.
[0054] Another sample was prepared by the conventional stir casting
method by melting 500 gms of aluminum to 9000 C. A mixture of 495 g
of K2TiF6 and 22 g of carbon powders were mixed and added to the
melt while stirring with graphite stirrer. The reaction was
completed in 20 minutes. Due to high viscosity of the melt,
skimming operation could not be carried out properly and some dross
was left within the melt. The melt was poured in a cast iron mould.
FIG. 4b shows a photograph of the casting.
Example 5
[0055] Aluminum composite sample, generally represented by numeral
104 was prepared by melting 530 gms of aluminum in a SiC crucible
at 950 C. 113 g of K2TiF6 powder was added to the melt and stirred
manually using an alumina rod. CO2 gas was bubbled through the
molten mixture for 10 minutes through an alumina lance submerged in
the melt. The crucible was then removed from the furnace, dross was
skimmed from the top of the melt and melt poured in cast iron
moulds. XRD analysis revealed the formation of TiC precipitates in
the casting and hardness was measured to be 48.2 Hv. Optical
micrograph of the sample is shown in FIG. 5.
Example 6
[0056] A melt comprising of aluminum and K2TiF6 was bubbled with a
mixture of CO2/N2 to produce Al--AlN--TiC composites.
Alternatively, air was used as carrier gas instead of argon in
Example 1 to produce Al--AlN--TiC composites.
Example 7
[0057] A Composite sample, generally represented by numeral 105 was
prepared using the method described in example 1. Additional
alloying additions of 0.5% Mg and 0.8% Si were made before pouring
the composite in moulds. Sample test samples were prepared from the
cast composite. The test samples were solutionized at 5500 C for 1
h and quenched in water. Solutionized samples were then heat
treated at 1700 C for different duration and hardness taken. The
aging curve is shown in FIG. 6.
Example 8
[0058] A number of composite samples were prepared by the method
described in example 1. The cast samples were machined into billet
form and extruded in the temperature range of 400 to 550 C in a die
to form extruded sections like rod and I-beam. FIG. 7 shows the
extruded products without any visual surface defects. Some of the
other samples were forged after preheating to 450 C and are shown
in FIG. 8.
TABLE-US-00001 TABLE 1 K2TiF6 Carbon Reaction Batch Hard- S. No
Matrix Preheating (g) (g) Process temp time ness Precipitates 1
Al-Si No 0 0 Lance 950 5 44.2 None 2 Pure No 0 0 Stirrer 950 20
30.0 None Al 3 Al-Si No 85 4 Present 900 20 59.2 TiC disclosure 4
Pure No 109 8 Present 900 18 42.2 TiC Al disclosure 5 6063 No 155
16 Present 900 15 36.9 TiC Al disclosure 6 Pure Yes 151 16 Stirrer
900 45 40.0 Al3Ti. Al TiC 7 Pure Yes 106.9 11 Stirrer 990 20 42.0
TiC Al 8 Pure Yes 107 11 Stirrer 900 20 40.1 Al3Ti. Al TiC
[0059] Analysis of the composites as tabulated in Table 1 shows
that the present disclosure allows composites with large volume
fraction of TiC precipitates to be prepared at lower temperatures,
in shorter cycle times and without the need for pre-heating the
precursor material.
[0060] Hardness of the composite prepared in accordance with the
present disclosure was found to be 59 Hv5 compared to 44 Hv5 for
Al--Si matrix using conventional technique. Hardness of composites
prepared by mechanical stirring under similar conditions have
hardness of 30 Hv5. Elastic modulus of the cast composite was
measured from tensile tests to be 90 GPa compared to 69 GPa for
pure aluminum.
[0061] Small pieces were cut from the cast ingot and hot forged at
450.degree. C. These samples showed no signs of cracking during hot
forging.
[0062] Sliding wear tests show significantly improved wear
performance; 1.14 mm3/km for the composite compared to 2.27 mm3/km
for pure aluminum.
[0063] While considerable emphasis has been placed herein on the
specific steps of the preferred process, it will be appreciated
that additional steps can be made and that many changes can be made
in the preferred steps without departing from the principles of the
disclosure. These and other changes in the preferred steps of the
disclosure will be apparent to those skilled in the art from the
disclosure herein, whereby it is to be distinctly understood that
the foregoing descriptive matter is to be interpreted merely as
illustrative of the disclosure and not as a limitation.
* * * * *