DESC:FORM-2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE
ALUMINIUM ALLOY COMPOSITION
APPLICANT
Hindalco Industries Limited,
of address
Ahura Centre, 1st Floor, B-Wing, Mahakali Caves Road, Andheri (EAST), Mumbal
Aditya Birla Science & Technology Co. Pvt. Limited
of address
Plot No. 1 & 1-A/1, MIDC Taloja, Taluka – Panvel, Dist. Raigad, Maharashtra 410208, India
COMPLETE SPECIFICATION
The following specification particularly describes this invention and the manner in which it is to be performed
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FIELD OF THE INVENTION
[1] The present invention relates to an aluminium alloy and a process for production of the same.
BACKGROUND OF THE INVENTION
[2] Aluminum alloys have long been used in the production of various articles such as vehicles, furniture, machinery, windows, doors etc.
[3] AA6xxx-series aluminum alloys have silicon and magnesium as major elements and are suitable for windows and door frames as they are easily extrudable and have a good surface finish.
[4] Globally the most common aluminium alloy used for fabricating window and door frames is AA6063 due to its medium strength and good response to surface finishing processes such as anodizing and powder coating. As per the Aluminum Association, AA6063 contains silicon 0.30% to 0.60%, magnesium 0.45% to 0.90%, iron <0.35%, manganese, copper, zinc, titanium each <0.1%, chromium <0.01%, other elements each <0.05% and the remainder is aluminum.
[5] Alloy properties such as surface quality and mechanical properties are the key requirements when used in window frames, door frames and other applications in building and construction industry.
[6] Yosuke Tamura et al., in their work “Use of KBF4–Al Mixed Powder to Produce Boron-Bearing 6063 Aluminum Alloys” in Materials Transactions, Vol. 59, No. 1 (2018) pp. 104 to 109 shown that in casting grade aluminum alloys with >7% Si, the surface smoothness and glossiness are improved by addition of Boron. Addition of boron enhances the aesthetics of the final anodized products made from the alloy. Adding boron to the aluminium alloy forms AIB2 and refines the solidification
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structures. These precipitates reduce the dendrite arms spacing in as-cast structure during solidification, which leads to reduction in final grain size. Finer grain size leads to higher impact resistance and toughness. Boron also improves the abrasion resistance and fretting resistance of aluminum alloys. These properties are beneficial in improving resistance of extruded profiles to surface scratches and dents.
[7] Improved surface quality implies lower surface roughness, lesser post-anodizing gloss and a uniform response to anodizing, without the presence of streaks or other defects, as desired in windows and doors for aesthetic purposes. Higher mechanical properties are desirable for higher load bearing capacity of the window and door frames. The new alloy will further improve the surface smoothness and gloss over the conventional alloy along with equal or better mechanical properties.
SUMMARY OF THE INVENTION
[8] It is therefore an object of the invention to provide an improved aluminium alloy composition having superior properties and performance compared to conventional extrusion alloys.
[9] An object of the invention is to provide an alloy that has improved surface properties and glossiness in extruded, anodized and powder coated aluminium profiles.
[10] Another object of the invention is to provide an alloy with higher hardness leading to improved abrasion resistance and fretting resistance of aluminum alloys.
[11] Yet another object of the invention is to provide an alloy with improved yield strength, tensile strength and elongation of the aluminium profiles
[12] Yet another object of the invention is to provide and alloy with desirable microstructural morphologies and final products having fine grain structure.
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[13] For achieving the above object, the invention provides aluminium alloy composition comprises of:
a) 0.3 to 1.3 wt% of Silicon;
b) 0.3 to 1.2 wt% of Magnesium;
c) up to 0.7wt% of Ferrous;
d) up to 1.0 wt% of Manganese;
e) up to 0.4 wt% of Copper;
f) up to 0.25wt% of Zinc;
g) up to 0.35wt% of Chromium;
h) up to 0.15wt% of Titanium;
i) 0.002 to 0.1wt% of Boron;
j) 0.002 to 0.1wt% of Strontium; and
k) the rest being aluminum.
[14] Additional objects and advantages of the invention will be set forth in the detailed description that follows, and in part will be obvious from the description, or maybe learned by practice of the invention. The objects and advantages of the invention will be attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[15] The foregoing summary, as well as the following detailed description of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of assisting in the explanation of the invention, the details are shown in the drawings embodiments which are presently preferred and considered illustrative. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown therein. In the drawings:
[16] Figure 1 is a graph showing the mechanical properties of aluminium alloy of present application compared to aluminium alloy 6063.
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BRIEF DESCRIPTION OF THE INVENTION
[17] In describing and claiming the invention, the following terminology will be used in accordance with the definitions set forth below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. As used herein, each of the following terms has the meaning associated with it in this section. Specific and preferred values listed below for individual process parameters, substituents, and ranges are for illustration only; they do not exclude other defined values or other values falling within the preferred defined ranges.
[18] As used herein, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise.
[19] The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention
[20] As used herein, the terms “comprising” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to.
[21] The term “aluminium alloy” as used herein refers to a chemical composition where other elements are added to pure aluminum in order to enhance its properties, primarily to increase its strength.
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[22] The term “surface smoothness” as used herein refers to the measure of the finely spaced micro-irregularities on the texture of a surface.
[23] The term “glossiness” as used herein refers to the measure of quality of a surface being smooth and shiny.
[24] The term “yield strength” as used herein is defined as the stress at which a predetermined amount of permanent deformation occurs.
[25] The invention is based on the object of preparing an aluminum alloy which is suitable for die-casting which is easy to cast, has a high elongation in the cast state and after casting ages no further. In addition, the alloy should be easily weldable and flangeable, able to be riveted and have good corrosion resistance.
[26] In an aspect, the invention provides aluminium alloy composition comprises of:
a) 0.3 to 1.3 wt% of Silicon;
b) 0.3 to 1.2 wt% of Magnesium;
c) up to 0.7wt% of Ferrous;
d) up to 1.0 wt% of Manganese;
e) up to 0.4 wt% of Copper;
f) up to 0.25wt% of Zinc;
g) up to 0.35wt% of Chromium;
h) up to 0.15wt% of Titanium;
i) 0.002 to 0.1wt% of Boron;
j) 0.002 to 0.1wt% of Strontium; and
k) the rest being aluminum.
[27] The process comprises of blending 0.002 to 0.10 wt.% boron (B) and 0.002 to 0.10 wt.% strontium (Sr) with a mixture comprising aluminum.
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[28] In an embodiment, preferably the composition comprises of 0.005 to 0.02 wt.% of Boron and 0.01 to 0.03 wt.% of strontium. More preferably the composition comprises of 0.01 wt.% of boron and 0.02 wt.% of strontium.
[29] Magnesium and silicon in the alloy facilitates strengthening of the alloy due to precipitation strengthening by Mg2Si formation under the presence of both elements. In an embodiment, preferable lower limit of magnesium is 0.40 wt.% to get the desired strength to the extruded profile. In another embodiment, the upper limit of amount of magnesium in the alloy is 1.00 wt.%. Excess magnesium may lead to formation of undesired Al-Fe-Mg second phase.
[30] In an embodiment, the lower limit of silicon is preferably 0.40 wt%. Presence of Si also enhance the extrudability of the alloy.
[31] In an embodiment, the amount of Fe in the alloy is preferably maintained in the range of 0.01 – 0.70 wt.%. The increase in Fe content may adversely affect the extrudability and mechanical properties which may not be compensated by other elements. On the other hand, low amount of Fe may lead to unwanted grain growth in the extruded profile adversely affecting the surface properties in the final product.
[32] Manganese and chromium content is essential in controlling the grain size in the final product made from the alloy composition. Manganese content is maintained in the range of 0.00 to 1.00 wt.% and preferred upper limit of Mn is 0.20 wt.%. The higher amount of manganese may interfere with the efficiency of strontium. In an embodiment, the maximum amount of Cr in the alloy is preferably 0.35 wt.%.
[33] In an embodiment, titanium is added for refining grain size during extrusion billet casting. In an embodiment, the amount of Ti in the alloy is in the range of 0.01 – 0.05 wt.% preferably 0.10 wt.%.
[34] In an embodiment, boron and strontium are added in an aluminum alloy melt in the form of master alloy containing 5% to 10% of boron or strontium with the balance
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being aluminium. Boron and Strontium are added after achieving the desired composition of Si, Mg, Fe, Mn, Cu, Ti in the aluminum melt.
[35] Boron and strontium can be included for an entire range of 6XXX series aluminum alloys i.e. 6060, 6063, 6061, 6082, 6101 etc. It is particularly useful for alloys used for building and construction applications such as 6063 and 6060. Most preferably, boron and strontium are included in AA6063 alloy. In an embodiment, Zn can be acceptable as impurity element up to 0.25 wt.%.
[36] 0.002 – 0.10 wt.% Sr in AA6xxx extrusion alloy promotes conversion of plate like ß-(AlxFeSi) phase to preferred fine a-(AlxFe2Si) phase. a-(AlxFe2Si) phase is more desirable phase for better surface properties and leads to better anodizing response. ß-(AlxFeSi) phase being more cathodic gets incorporated in the oxide film and are visible after anodizing while a-(AlxFe2Si) phase gets dissolved during etching before anodizing. Also a-(AlxFe2Si) phase is Si lean compared to ß-(AlxFeSi) phase and the excess Si is released during ß-phase to a-phase transformation. The additional Si leads to formation of more Mg2Si precipitates for strengthening. Excess amount of Si improves extrudability.
[37] In an embodiment, for as-cast extrusion billet of a 6xxx aluminum alloy, <60% a-phase transformation was observed for the billet with 200 ppm Sr as compared to <10% transformation for a billet of same alloy without Sr addition.
[38] Addition of 0.002 – 0.10 wt.% B to the aluminium alloy forms AIB2. The addition of B also forms SrB6 compounds which causes finer grain formation in the final product. SrB6 refines the solidification structures and also has a positive effect on eutectic phase modification. Finer grain size and modification of eutectic phase leads to improvement in metallurgical and mechanical properties in the final extruded profile. About 10% improvement in mechanical properties achieved in Sr and B containing alloy. Also, higher hardness values were achieved for Sr and B containing extruded alloy which would lead to better fretting resistance. Significantly lower gloss value also indicates the improvement in surface metallurgy in the final profile.
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[39] The aluminium alloy can be further extruded to form articles such as window frames, door frames and articles for other architectural applications.
[40] In application, a window profile is extruded from the aluminium alloy composition of present application. The process comprises of homogenizing casted aluminium alloy as mentioned in the aforesaid embodiments for uniform distribution and phase transformation to produce a desired phase. The desired phase is extruded, and a desired shape and size of the extruded material is obtained. The shaped material is subjected to heat treatment to improve the mechanical properties such as yield strength and tensile strength. The heat treatment is preferably solution heat treatment followed by artificial ageing.
[41] The heat-treated material is further anodized or subjected to powder coating for surface protection and for aesthetics.
[42] The aluminium alloy comprising boron and strontium provides an improved extruded profile. Particularly, surface smoothness and glossiness, abrasion resistance, impact resistance and toughness were found to be improved. Also, a uniform response to anodizing was observed.
[43] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the disclosure.
[44] The aforesaid components are essential to provide an aluminium alloy composition having superior benefits.
[45] Aluminium alloy of the present invention having crystal grain structure offers excellent performance. This aluminium alloy is used for making variety of
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applications, having good forgeability.
WORKING EXAMPLES
[46] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to a person skilled in the art, the invention should be construed to include everything within the scope of the disclosure.
[47] Aluminium alloys of present application comprising varying percentages of the ingredients are prepared. The percentage of the ingredients in aluminium alloy are provided in table 1.
Elements Trial-1 (Wt.%) Trial-2 (Wt.%) Silicon (Si) 0.42 0.41 lron (Fe) 0.11 0.081 Copper (Cu) 0.008 0.011 Manganese (Mn) 0.014 0.014 Magnesium (Mg) 0.49 0.48 Zinc (Zn) 0.003 0.003 Titanium (Ti) <0.001 0.002 Boron (B) 0.008 0.007 Strontium (Sr) 0.018 0.015
Table 1
[48] The tensile strength, yield strength, glossiness of the aluminium alloys of table 1 of present application is compared with other known aluminium alloys such as 6060, 6063, 6005, 6061, 6082, 6101.
[49] The compositions of the aluminium alloys 6060, 6063, 6005, 6061, 6082, 6101 are provided in table 2 below.
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Alloy
Si%
Fe%
Cu%
Mn%
Mg%
Cr%
Zn%
Ti%
Others
6063
0.3- 0.60
<0.35
<0.10
<0.10
0.45-0.9
<0.10
<0.10
<0.10
<0.05
6060
0.3-0.60
0.10-0.3
<0.10
<0.10
0.35-0.6
<0.05
<0.15
<0.10
<0.05
6005
0.60-0.9
<0.35
<0.10
<0.10
0.40-0.6
<0.1
<0.10
<0.10
<0.05
6061
0.40-0.8
<0.7
0.15-0.4
<0.15
0.8-1.2
0.04-0.35
<0.25
<0.15
<0.05
6082
0.7-1.3
<0.50
<0.10
0.4-1.0
0.6-1.2
<0.25
<0.25
<0.10
<0.05
6101
0.3-0.7
<0.5
<0.1
<0.03
0.35-0.8
<0.03
<0.10
-
<0.05
Table 2
[50] As shown in figure 1 and table 3, the aluminium alloy composition of present application exhibits enhanced tensile strength, yield strength and glossiness as compared with conventional Aluminium 6063 alloy.
Sample Tensile Strength (MPa) Yield Strength (MPa) Hardness (HV) 60° Gloss (etched) 60° Gloss (anodized) Regular- 6063 236 ± 7 211 ± 8 80 198 26 Trial-1 255 ± 4 232 ± 3 90 154 15.8 Trial-2 251 ± 1 228 ± 2 88 144 14.8
Table 3
[51] Boron forms SrB6 compounds which causes finer grain formation in the final product. SrB6 refines the solidification structures and also has a positive effect on eutectic phase modification. Finer grain size and modification of eutectic phase leads to improvement in metallurgical and mechanical properties in the final extruded profile. Table 3 highlights the grain size of the aluminium alloy as casted product and table 4 highlights the grain size of the aluminium alloy as extruded product.
Alloy
Sr (ppm)
B (ppm)
Grain Size (µm)
Trial 1 (as-cast)
280
160
580
Trial 2 (as-cast)
950
480
500
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Table 3
Alloy
Sr (ppm)
B (ppm)
Grain Size (µm)
Trial 1 (extruded)
0
0
115
Trial 2 (extruded)
180
80
100
Table 4
[52] Those skilled in the art can understand now from aforementioned discussion, and information in the present disclosure can be implemented in a variety of forms. Should be understood that this instruction aforementioned be described in be only in nature illustrate, therefore, the variant not departing from this instruction purport is intended in the scope of this instruction. These variants should not be regarded as a departure from the spirit and scope of this instruction.
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,CLAIMS:We Claim:
1) An aluminium alloy composition comprises of
a) 0.3 to 1.3 wt% of Silicon;
b) 0.3 to 1.2 wt% of Magnesium;
c) up to 0.7wt% of Ferrous;
d) up to 1.0 wt% of Manganese;
e) up to 0.4 wt% of Copper;
f) up to 0.25wt% of Zinc;
g) up to 0.35wt% of Chromium;
h) up to 0.15wt% of Titanium;
i) 0.002 to 0.1wt% of Boron;
j) 0.002 to 0.1wt% of Strontium; and
k) the rest being aluminum.
2) The composition as claimed in claim 1, wherein 60° gloss of extruded and anodized aluminium alloy is 10 to 35 GU.
3) The composition as claimed in claim 1, wherein hardness of extruded aluminium alloy is 80 to 105 HV.
4) The composition as claimed in claim 1, wherein tensile strength of extruded aluminium alloy is 230 to 350 MPa.
5) The composition as claimed in claim 1, wherein yield strength of extruded aluminium alloy is 200 to 310 MPa.
Dated this 09 July 2021
M. Kisoth
IN/PA-2259
Agent for the Applicant