Claims:We Claim

1 Aluminium alloy essentially comprising of magnesium (Mg) and silicon (Si) heat treated to derive micro-structure for automotive applications, wherein
said alloy has magnesium content in the range of 0.2 to 0.8 % by mass;
heat treated in a sequential steps of solutionising, quenching and aging; the solutionising is done in the range of 530 to 540 degree C followed by aging done in the range of 180 to 190 degree C; and
the micro-structure of the alloy is characterized by fine spheroids of silicon therein with
- secondary dendrite arm spacing (SDAS) in the range of 19.5 to 21.5 µm,
- mean diameter in the range of 1.10 to 2.30 µm, and
- roundness (R) in the range of 0.95 to 1.3.

2 The aluminium alloy as claimed in claim 1, wherein the silicon content is in the range of 4.0 to 8.0 % by mass.

3 The aluminium alloy as claimed in claim 2, wherein the said alloy comprises of copper (Cu) to some extent, preferably less than 0.2% by mass.

4 Aluminium alloy essentially comprising of copper (Cu) and silicon (Si) heat treated to derive micro-structure for automotive applications, wherein
said alloy has copper content in the range of 1.0 to 5.0 % by mass;
heat treated in a sequential steps of solutionising, quenching and aging; the solutionising is done in the range of 530 to 540 degree C and the aging is done in the range of 180 to 190 degree C; and
the micro-structure of the alloy is characterized by fine spheroids of silicon therein with
- secondary dendrite arm spacing (SDAS) lower than 25 µm,
- mean diameter less than 3.0 µm, and
- roundness (R) in the range of 1.4 to 2.0.

5. The aluminium alloy as claimed in claim 4, wherein the silicon content ranges from 4.0 to 8.0 % by mass.

6. The aluminium alloy as claimed in claim 5, wherein the said alloy comprises of magnesium (Mg) to some extent, preferably less than 0.5 % by mass.

7. Aluminium alloy essentially comprising of copper (Cu), magnesium (Mg) and silicon (Si) heat treated to derive micro-structure for automotive applications, wherein
said alloy has copper content in the range of 1.0 to 3.0 % by mass;
magnesium content in the range of 0.2 to 0.8 % by mass; and
heat treated in a sequential steps of solutionising, quenching and aging; the solutionising is done in the range of 530 to 540 degree C and the aging is done in the range of 180 to 190 degree C; and
the micro-structure of the alloy is characterized by fine spheroids of silicon therein with
- secondary dendrite arm spacing (SDAS) lower than 25 µm,
- mean diameter less than 2.5 µm, and
- roundness (R) in the range of 1.25 to 2.30.

8. The aluminium alloy as claimed in claim 7, wherein the silicon content ranges from 4.0 to 8.0 % by mass.

9. The aluminium alloy as claimed in claim 3 or 6 or 8, wherein the aluminium alloy is processed by gravity die casting method to manufacture automotive components.

Dated this 22nd day of Sept., 2020.

(Sahastrarashmi Pund)
Head – IPR
Endurance Technologies Ltd.

To,
The Controller of Patent,
The Patent Office, at Mumbai-400 037 , Description:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

TITLE OF THE INVENTION
“ALUMINIUM ALLOY FOR AUTOMOTIVE APPLICATIONS”

Endurance Technologies Limited
E-92, M.I.D.C. Industrial Area, Waluj, Aurangabad – 431136
Maharashtra, India

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of Invention

[001] The present invention is related to Aluminium alloy for automotive applications. More particularly, the present invention is related to Aluminium alloy that impart a unique micro-structure facilitating improved mechanical properties for automotive applications and requires less time for heat treatment.

Background of the Invention

[002] Aluminium alloys are alloys in which aluminium (Al) is the predominant metal. With the facet of light weighting in automotive industry for improved fuel economy, aluminium alloy is being accepted as an excellent alternative to steel for many applications. There are variety of Al alloys available in the public domain for variety of applications in various domains. The conventional aluminium alloys that are processed for use in automotive applications by the well-known die casting methods produces the end product bearing coarse crystal of eutectic Silicon along with Alpha Aluminium in their microstructure. The Al alloys with such microstructure are not bad for certain level of applications as it provides the required properties for non-critical applications.

[003] But such alloys face limitations when it comes for its application in automotive sub-components that particularly require to have greater ductility. None of the Al alloys of public domain, particularly processed by gravity die casting for automotive applications, can increase the ductility satisfactorily by addressing the problem of creation and persistence of the coarse crystal structure of eutectic Silicon in the final product.

[004] Therefore, there is a long pending unmet need to provide Aluminium alloy that imparts unique micro-structure in the end product leading to improved mechanical properties, specifically higher ductility. The unmet need is being addressed by the present invention as described below.

Objects of the Present Invention

[005] The main object of the present invention is to provide Aluminium alloy that imparts a unique micro-structure to the end product for automotive applications.

[006] Another object of the present invention is to provide Aluminium alloy that imparts unique micro-structure in the end product leading to improved mechanical properties, specifically higher ductility.

[007] Yet, another object of the present invention to provide Aluminium alloy for automotive applications, wherein the alloy has silicon content in the range of 4.0 to 8.0 % (by mass).

[008] Still the object of the present invention is to provide Aluminium alloy for automotive applications, wherein the alloy being processed easily by gravity die casting method to derive the desired mechanical properties.

Brief Description of the Drawings

[009] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein and advantages thereof will be better understood from the following description when read with reference to the following drawings, wherein

[0010] Figure 1 discloses the microstructure of an Aluminium alloy in accordance with the first embodiment (with Mg and Si) of the invention at 100x magnification.

[0011] Figure 2 shows the exploded view of microstructure of Fig. 1 at 500x magnification.

[0012] Figure 3 shows the microstructure of conventional aluminium alloy with coarse spheroids of silicon in the alloy wheel (prior art).

[0013] Figure 4 discloses the microstructure of aluminium alloy particularly in alloy wheel in accordance with the present invention wherein fully modified and fine spheroids of Si are clearly visible.

[0014] Figure 5 presents the microstructure of another embodiment of Aluminium alloy with Cu and Si in accordance with the invention at 100x magnification.

[0015] Figure 6 shows the exploded view of microstructure in Fig. 3 at 500x magnification.

[0016] Figure 7 describes the microstructure of the third embodiment of Aluminium alloy with Mg, Cu and Si in accordance with the invention at 100x magnification.

[0017] Figure 8 shows the exploded view of microstructure in Fig. 5 at 500x magnification.

Detailed Description of the Present Invention

[0018] The preferred embodiments of the invention will now be described along with the accompanying drawings. The preferred embodiment/s must not be viewed as restricting the scope and ambit of the invention.

[0019] In accordance with the present invention, the first embodiment of Aluminium alloy for automotive applications essentially comprises of Magnesium (Mg) and Silicon (Si). Magnesium (Mg) is being added to the aluminium alloy to increase the strength of alloy through solid solution strengthening due to its strain hardening ability. Silicon (Si) plays the role of improving fluidity of the alloy. The combination of magnesium (Mg) and silicon (Si) with aluminium in the alloy produces a precipitation hardening heat-treatable alloy making it applicable for automotive applications.

[0020] The content of magnesium (Mg) in Al alloy varies from 0.2 to 0.8 % (by mass) whereas that of Silicon (Si) is in the range of 4.0 to 8.0 % (by mass). However, copper (Cu) to some extent, preferably less than 0.2% (by mass), can be added to the Al alloy to balance the Aluminium alloy composition. Unavoidable impurities are kept to the minimum and are present in no more than trace quantities.

[0021] The above mentioned aluminium alloy, essentially comprising of Mg and Si, is heat treated to make it applicable for automotive components and bear the desired mechanical properties required therefor. The heat treatment comprises of sequential steps of solutionising, quenching and aging wherein the solutionising is done in the temperature range of 530 to 540 degree C and the aging is done in the range of 180 to 190 degree C. It reduces the time required for heat treatment drastically as compared to conventional methods of heat treatment and consequently helps to improve the productivity per unit time.

[0022] This Aluminium alloy essentially comprising Mg and Si, when processed by gravity die casting and heat treated as disclosed above, attains a microstructure having fine spheroids of silicon (Si) with secondary dendrite arm spacing (SDAS) less than 25 µm, mean diameter lower than 2.5 µm, and roundness (R) in the range of 0.95 to 1.30 as depicted in Figures 1 and 2. Figure 4 discloses the microstructure of aluminium alloy in accordance with the present invention particularly in alloy wheel wherein fully modified fine spheroids of Si are clearly visible. The roundness (R) of silicon (Si) spheroids is worked out as,
Roundness (R) = (P) 2/ (4p x A)
where, P – Perimeter of silicon spheroids in the micro-structure,
A – Area of silicon spheroids formed in the micro-structure.

[0023] The above mentioned aluminium alloy, essentially comprising of Mg and Si, is used for the manufacture of automotive components viz. alloy wheel, swing arm, etc. The automotive component, particularly alloy wheel of two wheeled vehicle, casted from above disclosed aluminium alloy, heat treated as disclosed imparting above described micro-structure exhibits the desirable mechanical properties viz. yield strength, tensile strength, elongation and hardness. The alloy wheel casted from aluminium alloy, almost seven samples selected randomly, were tested for these mechanical properties as per the standards recommended therefor. The alloy wheel was found to exhibit the Yield strength at 0.2 % in the range of 207 – 224 MPa, Tensile strength in the range of 275 – 294 MPa, Elongation in the range of 9.5 – 12.9 % and Hardness in the range of 88.0 to 91.0 BHN as shown in the following table.
Samples 0.2% Yield Strength (MPa) Tensile Strength (MPa) Elongation
(%) Hardness
(BHN)
1 207 275 10.4 90
2 210 291 11.2 90
3 212 291 10.5 89
4 213 294 11.1 89
5 212 285 9.8 89
6 221 292 9.5 89
7 224 291 14.8 90

[0024] Thus, the embodiment of aluminium alloy is novel in terms of its composition, technically advanced in terms of deriving a unique microstructure as specified above and technically superior in terms of at par mechanical properties being imparted in the casted components.

[0025] In another embodiment of the present invention, the Aluminium alloy for automotive applications essentially comprises of Copper (Cu) and Silicon (Si). Copper (Cu) is being added to the aluminium alloy to increase the strength of alloy and facilitate precipitation hardening. Silicon (Si) plays the role improving fluidity of the alloy. The combination of Copper (Cu) and silicon (Si) with aluminium in the alloy produces the highest strength heat treatable aluminium alloys making it applicable for automotive applications.

[0026] The content of Copper (Cu) in Al alloy varies from 1.0 to 5.0 % (by mass) whereas that of Silicon (Si) is in the range of 4.0 to 8.0 % (by mass). However, magnesium (Mg) to some extent, preferably less than 0.5% (by mass), can be added to the Al alloy to balance the Aluminium alloy composition. Unavoidable impurities are kept to the minimum and are present in no more than trace quantities.

[0027] This Aluminium alloy essentially comprising Cu and Si, when processed by gravity die casting and heat treated as disclosed above, attains a microstructure having fine spheroids of silicon (Si) with secondary dendrite arm spacing (SDAS) less than 25 µm, mean diameter lower than 3.0 µm, and roundness (R) in the range of 1.4 to 2.0 as depicted in Figures 5 and 6.

[0028] The above mentioned aluminium alloy, essentially comprising of Cu and Si, is used for the manufacture of automotive components viz. bottom case of suspension system, caliper body of brakes, etc. These automotive components casted from above disclosed aluminium alloy imparting above described micro-structure exhibits the desirable mechanical properties viz. yield strength, tensile strength, elongation and hardness. The automotive components were tested for these mechanical properties as per the standards recommended therefor and were found to exhibit the Yield strength at 0.2 % in the range of 190.0 to 217.0 MPa, Tensile strength in the range of 271.0 to 290.0 MPa, Elongation in the range of 2.9 to 3.7 % and Hardness in the range of 96.0 to 99.0 BHN as shown in the below table.
Samples 0.2% Yield Strength (MPa) Tensile Strength (MPa) Elongation
(%) Hardness
(BHN)
1 190.1 271.8 3.7 96.8
2 210.1 276.9 2.9 98.9
3 216.7 288.7 2.7 95.3
4 212.9 287.8 3.1 97.8
5 214.3 290.4 2.7 97.8

[0029] Still, in further embodiment in accordance with the present invention, the Aluminium alloy for automotive applications essentially comprises of Copper (Cu), Magnesium (Mg) and Silicon (Si) to produce high strength heat treatable aluminium alloys making it applicable for automotive applications. This embodiment of aluminium alloy comprises of Copper (Cu) content in the range of 1.0 to 3.0 % (by mass), magnesium (Mg) content in the range of 0.2 to 0.8 % (by mass) and that of Silicon (Si) in the range of 4.0 to 8.0 % (by mass). Unavoidable impurities are kept to the minimum and are present in no more than trace quantities.

[0030] Aluminium alloy of this embodiment essentially comprising Cu, Mg and Si, when processed by gravity die casting and heat treated as described above, attains a microstructure having fine spheroids of silicon (Si) with secondary dendrite arm spacing (SDAS) less than 25 µm, mean diameter lower than 2.5 µm, and roundness (R) in the range of 1.25 to 2.30 as depicted in Figures 7 and 8.

[0031] The above mentioned aluminium alloy, essentially comprising of Cu, Mg and Si, is used for the manufacture of automotive components viz. master cylinder of brakes, holder brackets of brakes, etc. These automotive components casted from above disclosed aluminium alloy imparting above described micro-structure exhibits the desirable mechanical properties viz. yield strength, tensile strength, elongation and hardness. The automotive components were tested for these mechanical properties as per the standards recommended therefor and were found to exhibit the Yield strength at 0.2 % in the range of 200.0 to 204.0 MPa, Tensile strength in the range of 276.0 to 294.5 MPa, Elongation in the range of 3.5 to 4.5 % and Hardness in the range of 91.0 to 93.5 BHN as shown in the below given table.

Samples 0.2% Yield Strength (MPa) Tensile Strength (MPa) Elongation
(%) Hardness
(BHN)
1 203.5 294.4 4.2 91.1
2 200.4 283.7 4.2 91.3
3 200.2 284.2 4.4 91.8
4 202.9 278.8 3.6 92.4
5 200.7 276.0 3.5 93.1

[0032] The technical advancements and benefits offered by the present disclosure include:
- The problem of creation and persistence of the coarse crystal structure of eutectic Silicon in final product is satisfactorily dealt with.
- All the three embodiments of aluminium alloy provides a unique micro-structure, each varying from the other, in the casted component and provides not only at par but superior mechanical properties.
- The disclosed aluminium alloys facilitate to use gravity die casting, a known process, thus leading to economical manufacturing of automotive components.
- The automotive components casted from the disclosed aluminium alloys of the invention take very less time for heat treatment actions, thus leading to less cycle time for production of the finished component.
- Aluminium alloys of the invention imparting a unique microstructure overcomes the deficiencies in characteristics of the existing Aluminium alloys without utilizing a time consuming and costly processing method.

[0033] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.