FORM 2
THE PATENT ACT 1970 (as amended)
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See Section 10: rule 13]
TITLE: “AN ALUMINIUM-BASED ALLOY COMPOSITION, A METHOD OF MANUFACTURING ALUMINUM-BASED ALLOY CASTING, AND ARTICLE
MANUFACTURED THEREOF”
Name of the Applicant: TATA MOTORS LIMITED
Address: Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001 Maharashtra, INDIA
Nationality: Indian
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

TECHNICAL FIELD
The disclosure relates to the technology of castable alloys, more particularly relates to designing aluminum alloy composition for enhanced mechanical properties by squeeze casting and heat treating aluminum alloy.
BACKGROUND
Aluminium alloys with silicon, copper and magnesium as alloying elements are used for automotive components. Manufacturing methods include Gravity Die Casting (GDC), Low Pressure Die Casting (LPDC) and High Pressure Die Casting (HPDC). Automotive industry due to commercial viability prefers Aluminium alloy AlSi9Cu3 for most of the cast aluminium parts. For aluminium alloy AlSi9Cu3 maximum tensile strength achievable by conventional casting processes is about 240 MPa with hardness up to 90 BHN. The cast components normally contain porosity due to gas entrapment or shrinkage during solidification. The porosity is detrimental for parts which are to be heat treated. The size of porosity can enlarge during heat treatment and subsequently proves to be more detrimental during service. Due to this limitation, Aluminium alloy components cannot be heat treated if components are not free of porosity. The demerits with conventional cast parts contain porosity which reduces strength of the parts. The porosity is more detrimental when the part is heat treated. Hence, the porosity reduces reliability of components after heat treating. The presence of porosity in heat treated parts makes it brittle and conventionally used chemical composition yields lower strength.
SUMMARY
Accordingly, the disclosure provides for an aluminum-based alloy composition comprising, copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6% w/w to about 12.0% w/w, iron ranging from about 0.0 % w/w to about 1.3% w/w, manganese ranging from about 0.0% w/w to about 0.5% w/w, magnesium ranging from about 0.0 % w/w to about 0.3% w/w, zinc ranging from about 0.0% w/w to about 1.0% w/w and nickel ranging from about 0.0% w/w to about 0.5% w/w, also provides for a method of manufacturing an aluminum-based alloy casting comprising composition copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0% w/w to about 1.3% w/w, manganese ranging from about 0.0% w/w to about 0.5% w/w, magnesium ranging from about 0.0% w/w to about 0.3% w/w, zinc ranging from about 0.0% w/w to about 1.0% w/w and nickel ranging from about 0.0% w/w to about 0.5% w/w,

wherein aluminum is base for the alloy composition, said method comprising acts of preparing molten metal from aforesaid composition, applying predetermined pressure onto die comprising the molten metal to squeeze cast the molten metal, and extracting the casting from the die and heat treating the casting to manufacture the aluminum-based alloy casting and also provides for an article manufactured from aluminum-based alloy casting comprising composition of copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0% w/w to about 1.3% w/w, manganese ranging from about 0.0% w/w to about 0.5% w/w, magnesium ranging from about 0.0% w/w to about 0.3% w/w, zinc ranging from about 0.0% w/w to about 1.0% w/w and nickel ranging from about 0.0% w/w to about 0.5% w/w.
DETAILED DESCRIPTION
The illustrative embodiments described in the detailed description, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, 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.
This disclosure is drawn, inter alia, to an aluminum-based alloy composition, a method of manufacturing aluminum-based alloy casting and an article manufactured using the aluminum-based alloy casting.
The purpose of the disclosure is to obviate the drawbacks of conventional casting processes. Another purpose is to design alloy composition within chemistry of AlSi9Cu3 which results in highest possible mechanical properties on heat treatment after squeeze casting. Yet another purpose is to keep cost low by restricting chemistry within given specifications of existing alloy, also without adding any extra element. The new alloy is comparable to commercially available alloys for auto parts, so that to prove economically a better solution.
The disclosure provides for designing chemistry of alloy and combining it with squeeze casting process to make the part amenable to heat treatment. Squeeze casting is a method of casting in which external pressure is applied while molten metal is solidifying in a mold. The applied external pressure reduces porosity in the cast parts.

The use of Aluminium parts reduces weight of vehicle which results in better fuel efficiency and compliance to superior exhaust norms. But, the Aluminium has certain limitations to be used as replacement for ferrous counter parts. These limitations are mainly attributed to lower strength and defects due to manufacturing processes. For cast parts one such limitation is gas porosity and shrinkage porosity. The appropriate selection of composition and manufacturing process parameters provides for aluminium parts to be superior choice over ferrous parts.
The Aluminium alloy cast is used to manufacture articles having tensile strength of the order of about 380 MPa and hardness of about 140 BHN which replace ferrous parts. Thus the weight of automobile having parts/articles manufactured using said aluminum alloy is reduced resulting in better fuel efficiency and improved compliance with exhaust norms. The weight reduction is achieved because of reduction in section size of components for materials with higher strength.
The aluminum alloy selected is AlSi9Cu3 with composition comprising, copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0% w/w to about 1.3% w/w, manganese ranging from about 0.0% w/w to about 0.5% w/w, magnesium ranging from about 0.0 % w/w to about 0.3% w/w, zinc ranging from about 0.0 % w/w to about 1.0% w/w and nickel ranging from about 0.0% w/w to about 0.5% w/w, wherein aluminum is base for the alloy composition.
In one embodiment the disclosure, to get improved mechanical properties, the Aluminum composition is restricted to preferred values. The aluminum-based alloy composition comprise, copper preferably ranging from about 2.0% w/w to about 2.5% w/w, silicon preferably ranging from about 10.0 % w/w to about 12.0% w/w, iron preferably ranging from about 0.6% w/w to about 0.8% w/w, manganese preferably ranging from about 0.0 % w/w to about 0.5% w/w, magnesium preferably ranging from about 0.25% w/w to about 0.3% w/w, zinc preferably ranging from about 0.0 % w/w to about 1.0% w/w and nickel preferably ranging from about 0.0 % w/w to about 0.5% w/w to obtain the alloy having tensile strength ranging from about 372 MPa to about 388 MPa at room temperature 25oC and hardness ranging from about 140 BHN to about 150 BHN.
In yet another embodiment of the disclosure provides for a method of manufacturing an aluminum-based alloy casting comprising composition copper ranging from about 1.5% w/w to

about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0 % w/w to about 1.3% w/w, manganese ranging from about 0.0 % w/w to about 0.5% w/w, magnesium ranging from about 0.0 % w/w to about 0.3% w/w, zinc ranging from about 0.0 % w/w to about 1.0% w/w and nickel ranging from about 0.0 % w/w to about 0.5% w/w, wherein aluminum is base for the alloy composition, said method comprising acts of preparing molten metal from aforesaid composition, applying predetermined pressure onto die comprising the molten metal to squeeze cast the molten metal, and extracting the casting from the die and heat treating the casting to manufacture the aluminum-based alloy casting.
In yet another embodiment of the disclosure the pressure is ranging from about 55 MPa to about 100 MPa for time durations sufficient to allow complete solidification of molten metal.
The manufacturing method is squeeze casting to reduce casting defects like porosity. Squeeze casting involves application of external pressure, in the range of 55 MPa to 100 MPa, during solidification of molten metal in mold. The cast part is then heat treated for solutionising and precipitation to enhance tensile strength and hardness. The solutionising is carried out at temperature range 530°C to 550°C for 4 hrs to 5 hrs. After solutionising the components immediately quenched in warm water at temperature between 50 °C to 75°C. Then artificial ageing is carried out at temperature range 220 °C to 240 °C. The cycle of heat treatment is referred to as heat treatment. The squeeze casting of aluminium alloys reduces porosity close to zero.
Heat Treatment is a process in which metals are alternately heated and cooled according to a preset schedule of time and temperature to improve the characteristics of the metal.
The Heat Treatment is a specific heat treatment process which may be applied to aluminum / copper / silicon alloys, such as hypereutectic, to increase the strength of the alloy by as much as 30%. In the case of T6 heat treatment, the process occurs in two phases.
The First Phase of T6 heat treatment is called the Quench Phase. In this phase the alloy is heated to 920 degrees Fahrenheit for 9 hours causing the copper in the alloy to become dissolved in the aluminum and forming what is called a “Single Phase Alloy”. If allowed to air cool naturally, the copper will tend to reconstitute, or reform itself within the alloy. However, when the heated alloy is cooled rapidly by water quenching the reformation of the copper is

retarded and the aluminum, supersaturated with copper, is locked into the “Single Phase Alloy” state.
In the Second Phase of the T6 heat treatment process, called the Aging Phase, the alloy is heated to 350 degrees Fahrenheit for 10 hours and then allowed to air cool. During this phase the copper combines with the aluminum in a process called “precipitation hardening” to form a copper aluminum crystal, CuAl2. It is the formation of these copper aluminum crystals which gives the alloy its strength.
The key to maximizing alloy strength comes from controlling the size of the copper / aluminum crystals. Maximum strength is attained when the size of the crystals, or precipitated particles, is kept very small forcing them to conform to the structure of the aluminum.
Precipitation hardening, also called age hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel and titanium, and some stainless steels. It relies on changes in solid solubility with temperature to produce fine particles of an impurity phase, which impede the movement of dislocations, or defects in a crystal’s lattice. Since dislocations are often the dominant carriers of plasticity, this serves to harden the material. The impurities play the same role as the particle substances in particle-reinforced composite materials. Just as the formation of ice in air can produce clouds, snow, or hail, depending upon the thermal history of a given portion of the atmosphere, precipitation in solids can produce many different sizes of particles, which have radically different properties. Unlike ordinary tempering, alloys must be kept at elevated temperature for hours to allow precipitation to take place. This time delay is called aging.
When a precipitation hardening alloy is quenched, its alloying elements will be trapped in solution, resulting in a soft metal. Aging a “solutionized” metal will allow the alloying elements to diffuse through the microstructure and form intermetallic particles. These intermetallic particles will nucleate and fall out of solution and act as a reinforcing phase, thereby increasing the strength of the alloy. Alloys may age “naturally” meaning that the precipitates form at room temperature, or they may age “artificially” when precipitates only form at elevated temperatures. In some applications, naturally aging alloys may be stored in a

freezer to prevent hardening until after further operations - assembly of rivets, for example, may be easier with a softer part.
In one more embodiment of the present disclosure provides for an article manufactured from aluminum-based alloy casting comprising composition of copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0 % w/w to about 1.3% w/w, manganese ranging from about 0.0 % w/w to about 0.5% w/w, magnesium ranging from about 0.0 % w/w to about 0.3% w/w, zinc ranging from about 0.0 % w/w to about 1.0% w/w and nickel ranging from about 0.0 % w/w to about 0.5% w/w.
The article is selected from group comprising automotive articles like supporting bracketeries for engine and gearbox and structural articles.
Aluminium alloys are used as raw material for automobile components/articles due to their higher strength to weight ratio. Pure aluminium has poor flowability and so inferior castability. Therefore, the silicon having composition of about 6% w/w to about 12% w/w is added to improve castability of the aluminum alloy. Further the addition of copper into the composition of aluminum alloy improves response to the heat treatment process. The magnesium when added in combination with silicon forms fine dispersion of intermetallic precipitate of Mg2Si. This very finely dispersed precipitate improves mechanical properties. The addition of magnesium improves tensile strength, this improvement in strength varies for different chemistries and section sizes.
Iron is detrimental impurity in aluminium alloys. Iron helps in countering casting problems like die sticking of casting, but, iron also forms coarse intermetallic compounds in cast aluminium. Because these intermetallic compounds are coarse they are considered to be discontinuity in matrix and hence content of iron should be restricted. If iron is restricted in the range of about 0.6% w/w to about 0.8% w/w to nullify the detrimental effect of iron. The iron forms coarse intermetallic compounds with other elements in the alloy. These coarse compounds act as discontinuity in the matrix and reduce strength of component to arrest problem of die sticking.

Advantages of squeeze casting are firstly, the squeeze casting reduces porosity from alloy casting and secondly the casting with reduced porosity is heat treated without reducing reliability of part.
Advantages of the chemical composition of aluminum alloy are firstly, the three elements are found to play more influential role in determining strength of aluminium alloy part after T6-heat treatment. Optimum iron content to reduce detrimental effect is ranging from about 0.6% w/w to about 0.8% w/w which significantly reduces detrimental effect of coarse intermetallic compounds. Secondly, presence of the iron prevents problems of metal sticking to die walls during ejection of hot component.
The Magnesium amount is ranging from about 0.25% w/w to about 0.3% w/w to get enhanced mechanical strength after T6 (solutionising & aging) heat treatment. Lower magnesium content, after solutionising and aging, results in reduced precipitates which reduce strength of the component. Higher magnesium content increases strength further but reduces ductility and makes the component brittle.
The Copper addition into the composition of alloy improves strength of the aluminum alloy but reduces ductility. Optimal addition of the copper is observed to be ranging from about 2% w/w to about 2.5% w/w.
Industrial applicability
The disclosed aluminum-based alloy with said composition finds potential application in manufacturing articles where weight reduction and enhanced mechanical properties is desirable. The disclosed aluminum-based alloy finds particular applicability in automotive industry, especially in manufacturing automotive articles. One skilled in the art will recognize, however, that the disclosed aluminum alloy could be utilized in relation to other systems that may or may not be associated with automotive industry. For example, the disclosed alloy could be utilized in relation to construction equipments or structural systems.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to disclosures containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or

both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim:
1. An aluminum-based alloy composition comprising:
a. copper ranging from about 1.5% w/w to about 3.5% w/w,
b. silicon ranging from about 6% w/w to about 12.0% w/w,
c. iron ranging from about 0.0 % w/w to about 1.3% w/w,
d. manganese ranging from about 0.0 % w/w to about 0.5% w/w,
e. magnesium ranging from about 0.0 % w/w to about 0.3% w/w,
f. zinc ranging from about 0.0 % w/w to about 1.0% w/w, and
g. nickel ranging from about 0.0 % w/w to about 0.5% w/w.
2. The alloy as claimed in claim 1, wherein said alloy has AlSi9Cu3 as the base.
3. The alloy as claimed in claim 1, wherein the alloy composition comprising:
a. copper preferably ranging from about 2.0% w/w to about 2.5% w/w,
b. silicon preferably ranging from about 10.0 % w/w to about 12.0% w/w,
c. iron preferably ranging from about 0.6% w/w to about 0.8% w/w,
d. manganese preferably ranging from about 0.0 % w/w to about 0.5% w/w,
e. magnesium preferably ranging from about 0.25% w/w to about 0.3% w/w,
f. zinc preferably ranging from about 0.0 % w/w to about 1.0% w/w, and
g. nickel preferably ranging from about 0.0 % w/w to about 0.5% w/w.
4. The alloy as claimed in claim 1, wherein said alloy has tensile strength ranging from about 372 MPa to about 388 MPa, preferably 380 MPa and hardness ranging from about 140 BHN to about 150 BHN, preferably 145 MPa.
5. A method of manufacturing an aluminum-based alloy casting comprising composition copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0% w/w to about 1.3% w/w, manganese ranging from about 0.0% w/w to about 0.5% w/w, magnesium ranging from about 0.0% w/w to about 0.3% w/w, zinc ranging from about 0.0% w/w to about 1.0% w/w and nickel ranging from about 0.0% w/w to about 0.5% w/w, wherein aluminum is base for the alloy composition, said method comprising acts of:
a. preparing molten metal from aforesaid composition,

b. applying predetermined pressure onto die comprising the molten metal to squeeze cast
the molten metal, and
c. extracting the casting from the die and heat treating the casting to manufacture the
aluminum-based alloy casting.
6. The method as claimed in claim 5, wherein the pressure is applied with hydraulic arrangement and is ranging from about 55 MPa to about 100 MPa.
7. The method as claimed in claim 5, wherein the heat treatment process comprises steps of solutionising-quenching-artificial ageing.
8. The method as claimed in claim 7, wherein the solutionising is carried out at temperature ranging from about 530°C to 550°C for about 4 hrs to about 5 hrs and quenching in warm water at temperature between 50°C to 75°C and artificial ageing is carried out at temperature range 220°C to 240°C.
9. An article manufactured from aluminum-based alloy casting comprising composition of copper ranging from about 1.5% w/w to about 3.5% w/w, silicon ranging from about 6 % w/w to about 12.0% w/w, iron ranging from about 0.0 % w/w to about 1.3% w/w, manganese ranging from about 0.0 % w/w to about 0.5% w/w, magnesium ranging from about 0.0 % w/w to about 0.3% w/w, zinc ranging from about 0.0 % w/w to about 1.0% w/w and nickel ranging from about 0.0% w/w to about 0.5% w/w.
10. The article as claimed in claim 9, wherein said article is selected from a group comprising automotive article and structural article.