TECHNICAL FIELD
The disclosure relates to an Alclad alloy plate and process of manufacturing thereof. An
Alclad alloy plate is manufactured by heating a base alloy slab of Al-Cu-Mn-Ti-V-Zr welded
with cladding alloy plate of Al-Zn followed by rolling. The resultant Alclad plate is subjected
to a suitable heat treatment to obtain desired strength level.
BACKGROUND OF DISCLOSURE
It is known in the art that Aluminium-copper-manganese-titanium-zirconium-vanadium (Al-
Cu-Mn-Ti-Zr-V) alloy based on AA2219 is a weldable, with medium to high strength and
can be produced via ingot metallurgical route. These alloys play a major role in various
applications wherein a combination of reasonable strength and weldability is required. These
alloys are commonly processed in the form of sheets, plates, extrusions, forgings, rolled
rings, etc. for various structural applications.
Few structural applications require processing of the Cu-rich alloy AA2219 alloys in
the form of plates. However, the Cu-rich alloy AA2219 suffers from poor general corrosion
resistance and, as a result, these alloys are cladded with Al-Zn based alloy (AA7072) to
protect the surfaces against general corrosion during long term storage in normal atmosphere
or during applications at elevated temperatures for small durations. The process for cladding
Al-Cu-Mn-Ti-Zr-V with Al-Zn to produce Alclad plate of suitable thickness with specific,
minimum tensile properties is a challenge and not disclosed in the art.
The AA2219 Alclad plates, once made are subjected to the T87 temper. The wellestablished
T87 temper is defined as solution treated, 7% cold worked and artificially aged to
attain the peak strength. On the other hand, the heat treatment temper T87 is defined in the
Aerospace Materials Specifications (AMS) 4295B, Feb 2006, for AA2219 sheet and plate as
“solution heat treated, stretched to produce approximately 8% permanent set and precipitation
hardened”. [Aerospace Materials Specification: AMS4295B, February 2006].
For a given aging schedule, the tensile strength properties of the plates may not
necessarily increase with increasing percentage of cold work beyond 7%. Further, it is to be
considered that the use of unidirectional stretching is often associated with an increase in
strength anisotropy in the corresponding heat treated material, i.e. the difference in strength
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properties between longitudinal direction (i.e. the stretching direction) and long transverse
direction increases with the use of stretching as high as 7% and beyond. Also, for flat
products with increased thicknesses and widths, the load requirement for the desired
percentage of cold work by stretching alone becomes very high. Therefore, there arises a
need for manufacturing Alclad plates having a desired thickness and peak strength that
involves combination of cold rolling and stretching techniques and thereby overcoming the
above mentioned limitations and is a better alternative solution to prior art problems.
For the present disclosure, at least 11 to 13 mm thick Alclad AA2219 plate is
required wherein 0.2% Proof stress (PS) of about 360 MPa, ultimate tensile strength (UTS) of
about 440 MPa and an elongation value of about 9% are required. The desired thickness
along with desired properties is obtained by the process comprising the combination of cold
rolling and stretching, wherein the combined percentage cold rolling and stretching is
preferably in the range of 7.0 to 7.3%.
SUMMARY OF THE DISCLOSURE
The disclosure relates to an Alclad alloy plates. The disclosure more particularly relates to a
process of manufacturing an Alclad alloy plates. A welded base alloy slab Al-Cu-Mn-Ti-VZr
(AA2219) is heated with cladding alloy plate Al-Zn (AA7072) at 515 ± 5°C for 20-24 h
followed by hot rolling, solution treatment, quenching, cold working and artificial aging (as
per T87 temper), thus producing Alclad plates of thicknesses ranging from 11 to 13 mm.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 represents an optical micrograph illustrating cladding thickness of 320 μm in 12.5
mm thick Alclad AA2219T87 plate as described in working example 1 according to one
embodiment described herein.
Figure 2 represents an optical micrograph illustrating cladding thickness of 320 μm in 12.5
mm thick Alclad AA2219T87 plate as described in working example 2 according to one
embodiment described herein.
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LIST OF TABLES
Table 1 illustrates T87 tensile properties in longitudinal (L) and long transverse (LT)
directions of the Alclad plate of the present invention as described in working example 1
according to one embodiment described herein.
Table 2 illustrates T87 tensile properties in longitudinal (L) and long transverse (LT)
directions of the Alclad plate of the present invention as described in working example 2
according to one embodiment described herein.
DETAILED DESCRIPTION OF DISCLOSURE
While the disclosure is susceptible to various modifications and alternative forms, specific
aspects thereof have been shown by way of examples. It should be understood, however that it is
not intended to limit the invention to the particular forms disclosed, but on the contrary, the
invention is to cover all modifications, equivalents, and alternative falling within the spirit and
the scope of the invention.
It is to be noted that a person skilled in the art can be motivated from the present
disclosure and modify the various steps of manufacturing Alclad plate. However, such
modification should be construed within the scope and spirit of the invention. Accordingly, the
examples are showing only those specific details that are pertinent to understanding the aspects
of the present invention so as not to obscure the disclosure with details that will be readily
apparent to those of ordinary skill in the art having benefit of the description herein.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to
cover a non-exclusive inclusion, such that a process comprises a number of steps does not
include only those steps but may include other not expressly listed or inherent to such
process.
The novel features which are believed to be characteristic of the disclosure will be
better understood from the following description when considered in connection with the
accompanying Tables and Figures. It is to be expressly understood, however, that each of the
figures is provided for the purpose of illustration and description only and is not intended as a
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definition of the limits of the present disclosure. It will be readily understood that the aspects
of the present disclosure, as generally described herein, and illustrated in the Tables and
Figures, can be arranged, substituted, combined, and designed in a wide variety of different
configurations, all of which are explicitly contemplated and make part of this disclosure.
Accordingly, the disclosure relates to a process of manufacturing Alclad plates of
thickness 11 to 13 mm comprising the steps of:
a. heating a welded base alloy slab Al-Cu-Mn-Ti-V-Zr with cladding alloy plate
Al-Zn at 515 ± 5°C for 20-24 h;
b. hot rolling the welded materials of step (a) to the reduction of thickness to 12
to 14 to produce Alclad plate,
c. subjecting the Alclad plate as obtained in step (b) to be solution treated at 535
± 5°C for 1 to 2 h, followed by quenching in water at ambient temperature;
d. subjecting the quenched Alclad plate of step (c) to cold working consisting of
combination of two steps; wherein the first step is of cold rolling followed by
second step of stretching, wherein the combined percentage of two steps of
cold working is in the range of 7.0 – 7.3% producing Alclad plates having
thicknesses of 11 to 13 mm.
In one embodiment of the disclosure, the process further comprises the step of artificial aging
at 160 °C to 170 °C for 20 to 25 h to attain desired peak strength.
In one embodiment of the disclosure, the process the cladding alloy plates are welded to top
and bottom sides of the base alloy slab at number of points.
In one embodiment of the disclosure, the cladding alloy plates and the base alloy slab are
cleaned appropriately to remove oxides, dirt, oil residue or impurities.
In one embodiment of the disclosure, the base alloy slab is heated at 475 to 495°C for 18 to
20 h.
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In one embodiment of the disclosure, the base alloy slab is having a thickness of 350 to 385
mm and subsequently hot rolling to reduction of thickness preferably in the range of 180-200
mm.
In one embodiment of the disclosure, the reductions to thickness varying from 5 to 15 mm
per rolling pass.
In one embodiment of the disclosure, the cladding alloy slab is heated at temperature in the
range of 450°C to 500°C, for 15 to 18 h.
In one embodiment of the disclosure, the cladding alloy slab is having a thickness of 350 to
400 mm and subsequently hot rolling to reduction of thickness in the range of 10-15 mm.
In one embodiment of the disclosure, the reductions to thickness varying from 20 to 40 mm
per rolling pass.
In one embodiment of the disclosure, the combined percentage of two steps of cold working
in step (d) is preferably in the range of 7.0 to 7.3%.
In one embodiment of the disclosure, in step (d) cold rolling is in the range of 4.8 to 5.5%
and stretching in the range of 2 to 2.5%.
In one embodiment of the disclosure, about 12.5 mm thick Alclad alloy plates having a
minimum 0.2% proof stress of 360 MPa, ultimate tensile strength (UTS) of about 440 MPa
and an elongation of about 9%.
In one embodiment of the disclosure, an Alclad plate of thickness 11 to 13 mm is produced.
In another aspect it discloses a process of manufacturing Alclad plates of thickness 11 to 13
mm comprising the steps of:
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a. heating a base alloy slab Al-Cu-Mn-Ti-V-Zr of thickness 350 to 400 mm at
temperature in the range of 475 to 495°C, for 16 to 24 h, and subsequently hot
rolling the slab to reduction of thickness to 180 -210 mm;
b. heating a cladding alloy slab Al-Zn of thickness 350 to 400 mm at temperature
in the range of 450 to 500°C, for 16 to 24 h and subsequently hot rolling a
plate to the reduction of thickness to 10 to 15 mm,
c. welding the cladding alloy plate Al-Zn to top and bottom sides of the base
alloy slab Al-Cu-Mn-Ti-V-Zr;
d. heating the welded base alloy slab – cladding alloy plate together at 515 ± 5°C
for 20-24 h;
e. hot rolling the welded materials of step (d) to the reduction of thickness to 12
to 14 mm thus produced Alclad plate,
f. subjecting the Alclad plate as obtained by step (e) to solution treatment at 535
± 5°C for 1 to 2 h, followed by quenching in water at ambient temperature;
g. quenching in water as treated Alclad plate of step (f) at ambient temperature;
h. subjecting the quenched Alclad plate of step (g) to cold working by a
combination of two steps; wherein first step is of cold rolling followed by
second step of stretching, wherein the combined percentage of two steps of
cold working is in the range of 7.0 to 7.3% and thus produced Alclad plate of
thickness 11 to 13 mm.
In yet another embodiment of the present disclosure, these alloys can be processed in the
form of sheets, plates, extrusions, forgings, rolled rings, etc. for various structural
applications.
In yet another embodiment of the present disclosure a process for manufacturing Alclad
plates by cladding Aluminium alloy such as Aluminium-Copper-Manganese-Titanium-
Zirconium-Vanadium (Al-Cu-Mn-Ti-Zr-V) (AA2219) with cladding material such as
Aluminium-Zinc alloy (AA7072) in the form of plate that is heat treated to T87 temper is
disclosed.
In yet another embodiment of the present disclosure a process of manufacturing an Alclad
alloy plate is disclosed, wherein the method comprising heating of a base alloy and cladding
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alloy at a predetermined temperature for a desired time period, welding together the base
alloy and the cladding alloy to obtain a base-cladding alloy that is heated and hot rolled to a
obtain the Alclad plate of desired thickness. Further, the Alclad plate is then subjected to
solution treatment followed by cold working and artificial aging.
The method comprising the steps of heating a base alloy AA2219 to first temperature
485 ± 5°C for a time period of 18 -20 hours and hot rolling down the base alloy to the
thickness of 200 mm with thickness reductions ranging from 5-15 mm per rolling pass. The
method further comprises heating cladding material or cladding alloy AA7072 to a second
temperature 470°C for a time period of 15 -18 hours and hot rolling down the cladding alloy
to the thickness of 11 mm. Upon rolling down the base alloy and the cladding alloy, the
surfaces of the base alloy and the cladding alloy are cleaned to remove dirt, oxides, oil and
any residue therein. Further, the method comprises welding the cladding alloy to the top and
bottom sides of the base alloy and heating the welded base alloy-cladding alloy together at a
third temperature of 515 ± 5°C for 20-24 hours.
The above heated base-cladding alloy is then subjected to hot rolling down to the
thickness of 13.50 mm with thickness reductions ranging from 20-40 mm per rolling pass and
produce the alclad plate that is solution treated at a fourth temperature of 535 ± 5°C for 1.5
hours followed by quenching in water at room temperature. Furthermore, the as-quenched
Alclad plate is then subjected to cold working by a combination of cold rolling (4.8 to 5.5%)
and stretching (2 to 2.5%) so as to maintain the total percentage of cold work within the range
of 7 – 7.3 %. The cold worked Alclad plate is then subjected to artificial aging process at a
fifth temperature of 163 ± 2°C for 23 to 25 hours producing an Alclad alloy plate of high
peak strength.
The above described procedure of producing Alclad alloy plates may be practiced up
to Alclad thickness of 6 - 30 mm and more which may be of commercial interest.
The present disclosure will now be illustrated with working examples which are
intended to illustrate the working of the invention and not intended to take restrictively to
imply any limitation on the scope of any invention.
EXAMPLE 1
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385 mm thick direct chill cast slabs of alloy AA2219 and AA7072, duly homogenized,
scalped and conforming to class ‘A’ quality of ultrasonic soundness were produced in Bharat
Aluminium Company (BALCO), Korba, qualified to produce aerospace grade wrought
aluminium alloys. The base alloy AA2219 had a composition of Al-comprising 6.2 wt% Cu,
0.34 wt% Mn, 0.07 wt% Ti, 0.16 wt% Zr, 0.10 wt% V and the cladding alloy AA7072 had a
composition of Al comprising1.09 wt% Zn. The base alloy had Fe and Si impurities to the
levels of 0.11 and 0.08 wt%, respectively, while the cladding alloy had Fe and Si impurity
contents of 0.18 and 0.10 wt%, respectively.
The base alloy AA2219 was heat treated to the temperature of 485 ± 5°C for 18-20 hours and
subsequently hot rolled to the thickness of 200 mm with reductions in thickness per rolling
pass ranging from 5-15 mm. The cladding alloy AA7072 was heated to the temperature
range of 460-470°C for 18-20 hours and subsequently hot rolled to 11 mm with reductions in
thickness per rolling pass ranging from 20-40 mm. The surfaces of resultant base alloy slab
and cladding alloy plate were appropriately cleaned to remove traces of oxides, dirt, oil
residue etc.
The cladding alloy plates having thickness of 11 mm were welded to top and bottom sides of
200 mm thick base alloy slabs. These welded materials were then heated to the temperature
of 515 ± 5°C for 20-24 hours, and subsequently hot rolled to the thickness of 13.5 mm with
reductions in thickness per rolling pass ranging from 20-40 mm thereby producing the Alclad
plate.
The Alclad plate was then solution treated at 535 ± 5°C for 1.5 hours and quenched in water
at ambient temperature. The as-quenched Alclad plate was subjected to cold work in two
steps including 5.3% cold rolling followed by 2% stretching thereby producing the cold
worked plate having a thickness of 12.5 mm. The cold work plate is then subjected to
artificial aging at 165°C for 24 hours. This heat treatment produced peak strength in the
Alclad plate. These materials were then utilized for evaluation of tensile properties.
EXAMPLE 2
385 mm thick direct chill cast slabs of alloy AA2219 and AA7072, duly homogenized,
scalped and conforming to class ‘A’ quality of ultrasonic soundness were produced in Bharat
Aluminium Company (BALCO), Korba, qualified to produce aerospace grade wrought
aluminium alloys. The base alloy AA2219 had a composition of Al-5.9 wt%; Cu-0.33 wt%;
10
Mn-0.08 wt%; Ti-0.17 wt%; Zr-0.11 wt%; V and the cladding alloy AA7072 had a
composition of Al-1.09wt%, Zn. The base alloy had Fe and Si impurities to the levels of 0.11
and 0.08 wt%, respectively, while the cladding alloy had Fe and Si impurity contents of 0.18
and 0.10 wt%, respectively.
The base alloy AA2219 was heat treated to the temperature of 485 ± 5°C for 18-20 hours and
subsequently hot rolled to the thickness of 200 mm with reductions in thickness per rolling
pass ranging from 5-15 mm. The cladding alloy AA7072 was heated to the temperature
range of 460-470°C for 18-20 hours and subsequently hot rolled to 11 mm with reductions in
thickness per rolling pass ranging from 20-40 mm. The surfaces of resultant base alloy slab
and cladding alloy plate were appropriately cleaned to remove traces of oxides, dirt, oil
residue etc.
The cladding alloy plates having thickness of 11 mm were welded to top and bottom sides of
200 mm thick base alloy slabs. These welded materials were then heated to the temperature
of 515 ± 5°C for 20-24 hours, and subsequently hot rolled to the thickness of 12.5 mm with
reductions in thickness per rolling pass ranging from 20-40 mm producing the Alclad plate.
The Alclad plate was then solution treated at 535 ± 5°C for 1.5 hours and quenched in water
at ambient temperature. The as-quenched Alclad plate was subjected to cold work in two
steps including 5.3% cold rolling followed by 2% stretching so as to produce the cold worked
plate having a thickness of 11.5 mm. The cold work plate was then subjected to artificial
aging at 165°C for 24 hours. This heat treatment produced peak strength in the Alclad plate.
These materials were then utilized for evaluation of tensile properties.
EVALUATION OF THE ALCLAD ALLOY
The tensile properties of the Alclad AA2219 alloy of the present invention were examined
using tensile tests carried out at ambient temperature on flat tensile specimens (50 mm gauge
length). Table 1 and Table 2 represent the tensile test results corresponding to working
examples 1 and 2, respectively. The tensile test results represent the peak strength properties
obtained in the T87 temper.
For the standard aging cycle of 24 hours at 165°C, increasing the total percentage of preaging
cold work from 7.5 to 8% has had the effect of decreasing the tensile properties.
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Studies showed that the use of 8% cold work introduced increased amounts of dislocations
that coarsened the strengthening precipitates and reduced tensile strength properties. For this
standard aging schedule, the combined percentage cold work was, therefore, kept between 7
and 7.3%.
Figure 1 and Figure 2 represent optical micrographs of cross-sections of Alclad plates, as
described in working examples 1 and 2, showing the cladding thicknesses of 320 μm and 400
μm, respectively. It may be noted that these cladding thicknesses are more than the minimum
required cladding thickness of 250 μm.
Table 1.Tensile Properties of Alclad alloy plate of working example 1
Serial No. Test Direction 0.2% PS (MPa) UTS (MPa) % elongation
1. L1 370 456 14
2. L2 368 453 12
3. L3 369 454 13
4. LT1 366 446 13
5. LT2 364 444 11
6. LT3 364 444 12
Table 2.Tensile Properties of Alclad alloy plate of working example 2
Serial No. Test Direction 0.2% PS (MPa) UTS (MPa) % elongation
1. L1 364 447 12
2. L2 369 433 13
3. L3 367 444 11
4. LT1 362 439 10
5. LT2 364 441 10
6. LT3 360 438 11

WE CLAIM
1. A process of manufacturing Alclad plates of thickness 11 to 13 mm comprising the
steps of:
a. heating a welded base alloy slab Al-Cu-Mn-Ti-V-Zr with cladding alloy plate
Al-Zn at 515 ± 5°C for 20-24 h;
b. hot rolling the welded materials of step (a) to the reduction of thickness to 12
to 14 to produce Alclad plate,
c. subjecting the Alclad plate as obtained in step (b) to be solution treated at 535
± 5°C for 1 to 2 h, followed by quenching in water at ambient temperature;
d. subjecting the quenched Alclad plate of step (c) to cold working consisting of
combination of two steps; wherein the first step is of cold rolling followed by
second step of stretching, wherein the combined percentage of two steps of
cold working is in the range of 7.0 – 7.3% producing Alclad plates having
thicknesses of 11 to 13 mm.
2. The process as claimed in claim 1, further comprises the step of artificial aging at 160
°C to 170 °C for 20 to 25 h to attain desired peak strength.
3. The process as claimed in claim 1, wherein the cladding alloy plates are welded to top
and bottom sides of the base alloy slab at number of points.
4. The process as claimed in claim 1, wherein the cladding alloy plates and the base
alloy slab are cleaned appropriately to remove oxides, dirt, oil residue or impurities.
5. The process as claimed in claim 1, wherein base alloy slab is heated at 475 to 495°C
for 18 to 20 h.
6. The process as claimed in claim 1, wherein base alloy slab is having a thickness of
350 to 385 mm and subsequently hot rolling to reduction of thickness preferably in
the range of 180-200 mm.