U.S. patent application number 15/127120 was filed with the patent office on 2017-04-13 for aluminum die-casting alloys.
The applicant listed for this patent is Diran Apelian, Makhlouf M. Makhlouf, Rheinfelden Alloys GmbH & Co. KG. Invention is credited to Diran Apelian, Makhlouf M. Makhlouf.
Application Number | 20170101703 15/127120 |
Document ID | / |
Family ID | 50693529 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170101703 |
Kind Code |
A1 |
Apelian; Diran ; et
al. |
April 13, 2017 |
Aluminum Die-Casting Alloys
Abstract
An aluminum die-casting alloy comprising: 1 to 6% by weight
nickel, 1 to 5% by weight manganese, 0.1 to 0.4% by weight
zirconium, 0.1 to 0.4% by weight vanadium, 0. 1 to 1% by weight
tungsten and/ or 0. 1 to 1% molybdenum, optionally up to 2% by
weight iron, optionally up to 1% by weight titanium, optionally up
to 2% by weight magnesium, optionally up to 0.5% by weight silicon,
optionally up to 0.5% by weight copper, optionally up to 0,5% by
weight zinc, optionally total maximum 5% by weight transition
elements including strontium, scandium, lanthanum, yttrium,
hafnium, niobium, tantalum, and/or chromium, and aluminum as the
remainder with further elements present as impurities due to
production such that the total maximum of impurity elements is 1%
by weight.
Inventors: |
Apelian; Diran; (West
Boylston, MA) ; Makhlouf; Makhlouf M.; (Shrewsbury,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apelian; Diran
Makhlouf; Makhlouf M.
Rheinfelden Alloys GmbH & Co. KG |
West Boylston
Shrewsbury
Rheinfelden |
MA
MA |
US
US
DE |
|
|
Family ID: |
50693529 |
Appl. No.: |
15/127120 |
Filed: |
February 27, 2015 |
PCT Filed: |
February 27, 2015 |
PCT NO: |
PCT/EP2015/054180 |
371 Date: |
September 19, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61970586 |
Mar 26, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22F 1/04 20130101; C22C
21/00 20130101 |
International
Class: |
C22F 1/04 20060101
C22F001/04; C22C 21/00 20060101 C22C021/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2014 |
EP |
14168188.2 |
Claims
1. An aluminum die-casting alloy comprising: 1 to 6% by weight
nickel, 1 to 5% by weight manganese, 0.1 to 0.4% by weight
zirconium, 0.1 to 4.4% by weight vanadium, at least one of 0.1 to
1% by weight tungsten and 0.1 to 1% molybdenum, optionally up to 2%
by weight iron, optionally up to 1% by weight titanium, optionally
up to 2% by weight magnesium, optionally up to 0.5% by weight
silicon, optionally up to 0.5% by weight copper, optionally up to
0.5% by weight zinc, optionally total maximum 5% by weight
transition elements selected from the group consisting of
strontium, scandium, lanthanum, yttrium, hafnium, niobium,
tantalum, and chromium, and aluminum as the remainder with further
elements present as impurities due to production such that the
total maximum of impurity elements is 1% by weight.
2. The aluminum die-casting alloy according to claim 1, comprising
4 to 6% by weight nickel.
3. The aluminum die-casting alloy according to claim 1, comprising
2 to 4% by weight manganese.
4. The aluminum die-casting alloy according to claim 1, comprising
0.2 to 0.8% by weight tungsten.
5. The aluminum die-casting alloy to claim 1, comprising 0.2 to
0.8% by weight molybdenum.
6. The aluminum die-casting alloy according to claim 1, comprising
0.1 to 0.3% by weight zirconium.
7. The aluminum die-casting alloy according to claim 1, comprising
0.3 to 0.4% by weight vanadium.
8. The aluminum die-casting alloy according to claim 1, including
substantially uniformly dispersed particles of
Al.sub.3V.sub.xZr.sub.1-x, where x is a fraction of unity that
depends on the ratio of Zr:V in the alloy, the particles having an
equivalent diameter of less than about 50 nm.
9. The aluminum die-casting alloy according to claim 1, including
particles of Al.sub.3Ni having an equivalent diameter of less than
about 500 nm.
10. The aluminum die-casting alloy according to claim 1, including
substantially uniformly dispersed particles of
Al.sub.12Mn.sub.1-xW.sub.x, where x is a fraction of unity that
depends on the ratio of W:Mn in the alloy, the particles having an
equivalent diameter of less than about 500 nm.
11. The aluminum die-casting alloy of claim 10, wherein the
Al.sub.12Mn.sub.1-xW.sub.x, particles have a body centered cubic
crystal structure.
12. The aluminum die-casting alloy of claim 10, wherein the
al.sub.12Mn.sub.1-xW.sub.x particles are semi-coherent with the
aluminum matrix.
13. The aluminum die-casting alloy according to claim 1, including
substantially uniformly dispersed particles of
Al.sub.12Mn.sub.1-xMo.sub.x where x is a fraction of unity that
depends on the ratio of Mo:Mn in the alloy, the particles having an
equivalent diameter of less than about 500 nm.
14. The aluminum die-casting alloy of claim 13, wherein the
Al.sub.12Mn.sub.1-xMo.sub.x particles have a body centered cubic
crystal structure.
15. The aluminum die-casting alloy of claim 13, wherein the
Al.sub.12Mn.sub.1-xMo.sub.x particles are semi-coherent with the
aluminum matrix.
16. The aluminum die-casting alloy according to claim 1, including
substantially uniformly dispersed particles of
Al.sub.12Mn.sub.1-x-yW.sub.xMo.sub.y, where x and y are fractions
of unity that depend on the ratio of W:Mo:Mn in the alloy, the
particles having an equivalent diameter of less than about 500
nm.
17. The aluminum die-casting alloy of claim 16, wherein the
Al.sub.12Mn.sub.1-x-yW.sub.xMo.sub.y particles have a body centered
cubic crystal structure.
18. The aluminum die-casting alloy of claim 16, wherein the
Al.sub.12Mn.sub.1-x-yW.sub.xMo.sub.y particles are semi-coherent
with the -aluminum matrix.
19. A high pressure die-cast component made from an aluminum alloy
according to claim 1.
20. A cast component made from an aluminum alloy according to claim
1 where in the alloy is solidified in a metal water-cooled
mold.
21. A method of producing a cast component made from an aluminum
alloy according to claim 1, wherein the alloy is age-hardened by
holding the solidified cast component at a temperature of
350.degree. C. to 450.degree. C. for 2 to 12 hours.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to aluminum alloys that are
dispersion-strengthened, age-hardenable, and can be processed by
die-casting into shaped objects that have useful mechanical
properties at temperatures up to at least 350.degree. C.
BACKGROUND OF THE INVENTION
[0002] Automotive engines made with aluminum alloys have a high
power-to-weight ratio, and therefore they have better fuel
efficiency and less negative impact on the environment than cast
iron engines. However, with the demand for yet higher fuel
efficiencies, `super-charged` engines are being designed to operate
at even higher temperatures than regular engines. Accordingly,
cylinder heads and engine blocks in `supercharged` engines are
subjected to thermal cycling over a wider temperature range, and
the alloy used in their construction has to withstand the resulting
severe thermo-mechanical loading over long periods of time.
Conventional casting aluminum alloys are not capable of
withstanding these temperatures because their precipitation
hardening effects disappear at about 200.degree. C. Consequently,
the dimensional stability, strength, and durability of cylinder
heads and engine blocks made with these alloys become compromised
at the elevated temperatures that are encountered during the
operation of `supercharged` engines. Supercharged engines and
cylinder heads are not the only automotive components that could
benefit from an aluminum alloy that is specifically designed for
service at elevated temperatures. Connecting rods, impellers, brake
calipers, and brake rotors could also benefit from such an alloy.
Therefore, there is a need for a light, thermally stable alloy that
is designed specifically for such applications.
PRIOR ART
[0003] Several attempts have been made in the past to provide
aluminum casting alloys with enhanced thermal stability. Most
notable among these attempts are alloys described in WO
2011/124590, which is therewith incorporated by reference.
[0004] When properly processed, the alloys represented in WO
2011/124590 have better mechanical properties at elevated
temperatures than traditional aluminum casting alloys. However, and
because the volume fraction of the fine zirconium-vanadium
tri-aluminide (Al.sub.3V.sub.1-xZr.sub.x) particles in the prior
art alloys do not exceed 1% by volume; they have a limited
strengthening effect. For this reason, an option of the prior art
invention calls for adding up to 5% by weight manganese to the
alloy. Upon aging at a temperature between 350.degree. C. and
450.degree. C., manganese, together with aluminum, forms metastable
manganese aluminide particles (Al.sub.12Mn) that further increase
the strength of the alloy. However, although these additional
precipitate particles add strength to the alloy at room
temperature, their strengthening effect disappears with increased
service time at elevated temperatures.
DISCLOSURE OF THE INVENTION
[0005] The present invention relates to a class of aluminum alloys
that (i) are dispersion-strengthened, (ii) can be processed by
die-casting to produce useful shaped objects, and (iii) can be
age-hardened for improved room temperature mechanical properties
that are retained at temperatures up to at least 350.degree. C.
[0006] It is an objective of the present invention to provide
lightweight, wear-resistant, and corrosion-resistant materials that
can be cast into useful objects by the conventional die-casting
process and that are thermally stable up to at least 350.degree.
C.
[0007] Alloys of the present invention have the general chemical
composition:
aluminum-nickel-manganese-tungsten/molybdenum-zirconium-vanadium,
and their chemical composition is optimized such that their
liquidus temperature is less than 725.degree. C. Such low liquidus
temperature allows the alloys of the present invention to be
processed into useful objects by traditional high-pressure
die-casting.
[0008] Unlike traditional aluminum-silicon alloys, and similar to
alloys of the prior art article, alloys of the present invention
contain a eutectic structure that is stable at temperatures
approaching 640.degree. C., and it contains strengthening
precipitate particles that are thermally stable at temperatures
approaching 350.degree. C. Also similar to alloys of the prior art
article, the microstructure of the aluminum alloys of the present
invention contains nickel trialuminide and aluminum as its eutectic
structure, together with other transition metal trialuminide
particles, namely Al.sub.3V.sub.1-xZr.sub.x. These transition metal
trialuminide particles have the highly symmetric L1.sub.2 crystal
structure, which is analogous to the face centered cubic crystal
structure of aluminum. It is this similarity in crystal structure
between the aluminum matrix and these strengthening particles that
allows for a coherent interface between the two phases; and by
doing so, it maximizes the strengthening ability of the particles,
impedes their coarsening, and enhances the thermal stability of the
alloy.
[0009] A feature of the alloys of the present invention that
distinguishes them from the prior art aluminum alloys that contain
nickel, vanadium, and zirconium together with manganese, but
without tungsten is that in the alloys of the present invention,
the Al.sub.3V.sub.1-xZr.sub.x particles are not the only thermally
stable strengthening precipitates in the alloy. Alloys of the
present invention rely on a relatively large amount of
Al.sub.12Mn.sub.1-xW.sub.x precipitate particles for added strength
at elevated temperature. Alloys of the present invention also rely
on carefully designed tungsten containing manganese-aluminide
(Al.sub.12Mn.sub.1-xW.sub.x) precipitate particles for strength at
elevated temperature. Al.sub.12Mn.sub.1-xW.sub.x precipitate
particles have the body centered cubic crystal structure, which is
akin to the face centered cubic crystal structure of the
.alpha.-aluminum matrix; and therefore they are semi-coherent with
the .alpha.-aluminum matrix. Moreover, Al.sub.12Mn.sub.1-xW.sub.x
particles do not readily coarsen when exposed to elevated
temperatures and therefore--as shown in FIG. 1--unlike the aluminum
alloys of the prior art, alloys of the present invention retain a
significant fraction of their room temperature mechanical
properties at elevated temperatures.
[0010] The main feature of the alloys of the present invention that
distinguishes them from those of the prior art is that alloys of
the present invention contain tungsten and/or molybdenum. For this
reason, in alloys of the present invention, the
Al.sub.3V.sub.1-xZr.sub.x particles are not the only thermally
stable strengthening precipitates. Because of their small quantity
in the alloy (.ltoreq.1% by volume), by themself the
Al.sub.3V.sub.1-xZr.sub.x particles can contribute only limited
high temperature strength. Alloys of the present invention rely on
a relatively large amount of Al.sub.12Mn.sub.1-xW.sub.x precipitate
particles for added strength at elevated temperature.
[0011] In general, when precipitation-strengthened aluminum alloys
are subjected to high temperature during service, the metastable
precipitates that were formed by thermal aging coarsen and begin to
transform into the stable phase. When this happens, the alloy
begins to lose its strength. Therefore, precipitates that have a
low coarsening rate have enhanced thermal stability, and alloys
that employ such precipitates for strengthening have good tensile
properties at high temperature. FIG. 1 shows that the measured
yield strength at elevated temperatures of the
Al-6Ni-4Mn-0.7W-0.4V-0.1Zr alloy of the present invention is 90 MPa
at 300.degree. C., which is significantly higher than that of the
Al-6Ni-0.4V-0.1 Zr alloy of the prior art, which is only 60 MPa at
300.degree. C. The reason for this distinguishing feature of the
present invention alloy is described in detail in the following
paragraphs.
[0012] The precipitation sequence during thermal aging of binary
Al--Mn alloys starts with formation of metastable Al.sub.12Mn
particles. These particles are, to a large extent, responsible for
the observed strength of thermally aged binary Al--Mn alloys. With
extended time at an elevated temperature, these metastable
Al.sub.12Mn particles coarsen and eventually they transform to the
stable Al.sub.6Mn phase. The Al.sub.6Mn particles have the
rhombohedral crystal structure, and therefore they have incoherent
interfaces with the surrounding .alpha.-aluminum matrix.
Transformation of the metastable, semi-coherent Al.sub.12Mn
particles into stable, incoherent Al.sub.6Mn particles signals the
loss of their strengthening effect.
[0013] The present invention capitalizes on the fact that the
lattice of the metastable Al.sub.12Mn phase is similar to that of
the Al.sub.12W phase (both are body centered cubic), and also on
the fact that the lattice parameter of the Al.sub.12Mn phase (0.754
nm) is close to that of the Al.sub.12W phase (0.758 nm). For these
two reasons, during precipitation from the super saturated solid
solution, tungsten can dissolve into the Al.sub.12Mn phase to form
Al.sub.12Mn.sub.1-xW.sub.x co-precipitates. Similar to the
Al.sub.12Mn particles, the Al.sub.12Mn.sub.1-xW.sub.x particles
have body centered cubic lattice structure and semi-coherent
interfaces with the .alpha.-aluminum matrix.
[0014] However, thermodynamic calculations show that dissolution of
tungsten into Al.sub.12Mn lowers the Gibbs free energy of the
thus-formed Al.sub.12Mn.sub.1-xW.sub.x particles relative to the
Gibbs free energy of Al.sub.12Mn. This makes the
Al.sub.12Mn.sub.1-xW.sub.x particles more resistant to coarsening
when exposed to elevated temperature, and therefore less prone to
transforming into the incoherent Al.sub.6Mn phase, than the
Al.sub.12Mn particles.
[0015] A comparable effect on the strength at elevated temperatures
can be observed with an addition of molybdenum or a combined
addition of tungsten and molybdenum.
[0016] The foregoing objective is achieved according to the present
invention by an aluminum die-casting alloy comprising the
following:
[0017] 1 to 6% by weight nickel,
[0018] 1 to 5% by weight manganese,
[0019] 0.1 to 0.4% by weight zirconium,
[0020] 0.1 to 0.4% by weight vanadium,
[0021] 0.1 to 1% by weight tungsten and/or 0.1 to 1% by weight
molybdenum,
[0022] optionally up to 2% by weight iron,
[0023] optionally up to 1% by weight titanium,
[0024] optionally up to 2% by weight magnesium,
[0025] optionally up to 0.5% by weight silicon,
[0026] optionally up to 0.5% by weight copper,
[0027] optionally up to 0,5% by weight zinc,
[0028] optionally total maximum 5% by weight transition elements
including strontium, scandium, lanthanum, yttrium, hafnium,
niobium, tantalum, and/or chromium, and aluminum as the remainder
with further elements present as impurities due to production such
that the total maximum of impurity elements is 1% by weight.
[0029] In a preferred embodiment the aluminum die-casting alloy
comprises 4 to 6% by weight nickel.
[0030] In a preferred embodiment the aluminum die-casting alloy
further comprises 2 to 4% by weight manganese.
[0031] In a further preferred embodiment the aluminum die-casting
alloy comprises 0.2 to 0.8% by weight tungsten.
[0032] In a further preferred embodiment the aluminum die-casting
alloy comprises 0.2 to 0.8% by weight molybdenum.
[0033] In a further preferred embodiment the aluminum die-casting
alloy comprises 0.1 to 0.3% by weight zirconium.
[0034] In a further preferred embodiment the aluminum die-casting
alloy comprises 0.3 to 0.4% by weight vanadium.
[0035] According to one embodiment the aluminum die-casting alloy
includes substantially uniformly dispersed particles of
Al.sub.3V.sub.xZr.sub.1-x, where x is a fraction of unity that
depends on the ratio of Zr:V in the alloy. The particles having an
equivalent diameter of less than about 50 nm, preferably less than
about 30 nm, more preferably less than about 10 nm, particularly
less than about 5 nm.
[0036] In a further embodiment the aluminum die-casting alloy
includes particles of Al.sub.3Ni having an equivalent diameter of
less than about 500 nm, preferably less than about 300 nm,
particularly less than about 100 nm.
[0037] In a further embodiment the aluminum die-casting alloy
includes substantially uniformly dispersed particles of
Al.sub.12Mn.sub.1-xW.sub.x, where x is a fraction of unity that
depends on the ratio of W:Mn in the alloy, the particles having an
equivalent diameter of less than about 500 nm, preferably less than
about 300 nm, particularly less than 100 nm. The
Al.sub.12Mn.sub.1-xW.sub.x particles have a body centered cubic
crystal structure. The Al.sub.12Mn.sub.1-xW.sub.x particles are
semi-coherent with the .alpha.-aluminum matrix.
[0038] In a further embodiment the aluminum die-casting alloy
includes substantially uniformly dispersed particles of
Al.sub.12Mn.sub.1-xMo.sub.x, where x is a fraction of unity that
depends on the ratio of Mo:Mn in the alloy, the particles having an
equivalent diameter of less than about 500 nm, preferably less than
about 300 nm, particularly less than 100 nm. The
Al.sub.12Mn.sub.1-xMo.sub.x particles have a body centered cubic
crystal structure. The Al.sub.12Mn.sub.1-xMo.sub.x particles are
semi-coherent with the .alpha.-aluminum matrix.
[0039] In a further embodiment the die casting alloy includes
substantially uniformly dispersed particles of
Al.sub.12Mn.sub.1-x-yW.sub.xMo.sub.y, where x and y are fractions
of unity that depend on the ratio of W:Mo:Mn in the alloy, the
particles having an equivalent diameter of less than about 500 nm,
preferably less than about 300 nm, particularly less than 100 nm.
The Al.sub.12Mn.sub.1-x-yW.sub.xMo.sub.y particles have a body
centered cubic crystal structure. The
Al.sub.12Mn.sub.1-x-yW.sub.xMo.sub.y particles are semi-coherent
with the .alpha.-aluminum matrix.
[0040] In a further embodiment of the invention a high pressure
die-cast component is made is made of the alloy according to the
invention.
[0041] In a further embodiment of the invention the aluminum
die-casting alloy is solidified in a metal water-cooled mold.
[0042] In a method according to the invention a cast component is
made from an aluminum die-casting alloy according to the invention,
wherein the alloy is age-hardened by holding the solidified cast
component at a temperature of 350.degree. C. to 450.degree. C. for
2 to 12 hours.
[0043] According to one embodiment the aluminum alloy comprises 5.5
to 6.0% by weight nickel, 1.75 to 2.0% by weight manganese, 0.1 to
0.3% by weight of zirconium, 0.3 to 0.4% by weight of vanadium and
0.3 to 0.4% by weight tungsten.
[0044] According to a further embodiment the aluminum alloy
comprises 5.75 to 6.00% by weight nickel, 3.75 to 4.25% by weight
manganese, 0.3 to 0.4% by weight of vanadium, 0.1 to 0.2% by weight
zirconium, 0.25 to 0.30% by weight tungsten, 0.25 to 0.30 by weight
molybdenum and Al as remainder.
EXAMPLE
[0045] The following example is intended to illustrate the present
invention and it is by no means restrictive thereof.
[0046] Measured amounts of aluminum-nickel, aluminum-manganese,
aluminum-zirconium, and aluminum-vanadium master alloys, together
with pure tungsten powder were added to commercially pure aluminum
in order to constitute an alloy of the present invention with the
nominal chemical composition: Al-6Ni-4Mn-0.8W-0.4V-0.1Zr. This
alloy was melted in an induction furnace at 850.degree. C. for
sufficient time to allow dissolution of the master alloys and
tungsten powder into the commercially pure aluminum, and
homogenization of the resulting melt. The melt temperature was then
lowered to 750.degree. C., and the melt was degassed for 30 minutes
with argon utilizing a rotating impeller degasser. After degassing,
the melt was poured into a water-cooled copper mold to produce
disk-shaped castings that were then machined into ASTM standard
sub-size tensile test specimens. The tensile test specimens were
aged in an electric box furnace at 450.degree. C. for 10 hours and
then divided into four groups each group containing six identical
specimens. The elevated temperature yield strength of each group of
specimens was measured by means of an Instron Universal Testing
machine. Prior to performing the measurements, the tensile
specimens were soaked in an electric box furnace at the following
test temperatures for 100 hours; and during the test, each tensile
specimen was soaked in the furnace of the Instron Universal Testing
machine at the test temperature for an additional 30 minutes in
order to allow the specimen to equilibrate at the test
temperature.
TABLE-US-00001 Group No. Temperature (.degree. C.) 1 25 2 300 3 350
4 400
[0047] FIG. 3 shows the change in the measured yield strength of
the Al-6Ni-4Mn-0.8W-0.4V-0.1Zr alloy of the present invention
compared to that of 380-F and 356-T6 commercial aluminum-silicon
alloys. Clearly, the alloy of the present invention outperforms
both commercial alloys at all temperatures above 150.degree. C.
DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 is a chart that shows the change in measured yield
strength with temperature for the Al-6Ni-0.7W-0.4V-0.1Zr alloy of
the present invention and the Al-6Ni-0.4V-0.1Zr alloy of the prior
art: At all temperatures, the measured yield strength of the alloy
of the present invention is higher than that of the alloy of the
prior art.
[0049] FIG. 2 is a chart that shows the change with soak time in
measured yield strength for the binary Al-2Mn and ternary
Al-2Mn-0.75W alloys. The samples were soaked at 450.degree. C. for
the various times and their yield strength was measured at room
temperature: While the measured yield strength of the binary Al-2Mn
alloy decreases rapidly when the alloy is held at 450.degree. C.,
the measured yield strength of the ternary Al-2Mn-0.75W alloy does
not degrade with time up to 250 hours, beyond which time the
experiment was terminated.
[0050] FIG. 3 is a chart that shows the change with temperature in
measured yield strength of some commercial alloys compared to that
of the alloy of the present invention. The tensile test specimens
were soaked at the test temperature for 100 hours and tested at the
soak temperature. Chart legend: 380-F.ident.standard
aluminum-silicon alloy with nominal chemical composition
Al-8.5Si-3.5Cu in the as-cast condition, 356-T6.ident.standard
aluminum-silicon-magnesium alloy with nominal chemical composition
Al-7Si-0.35Mg-0.2Cu heat-treated according to the T6 schedule,
HPDC.ident.high-pressure die-casting, and PM.ident.permanent mold
casting. The data source for the 380-F and 356-T alloys is Kaufman,
J. G. and Rooy, E. L., Aluminum Alloy Castings: Properties,
Processes, and Applications, A F S, Schaumberg, I L (2004).
* * * * *