GB2568095A

GB2568095A - An aluminium alloy for high pressure die casting

Info

Publication number: GB2568095A
Application number: GB1718332.8A
Authority: GB
Inventors: Blake Paul; Ji Shouxun; Ian Zhu Xiangzhen
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-11-06
Filing date: 2017-11-06
Publication date: 2019-05-08
Also published as: GB201718332D0

Abstract

An aluminium alloy which comprises (by weight) 7.5-12.5 % silicon, 2.0-5.5 % copper and 0.3-1.6 % magnesium, with the balance being aluminium. The alloy can further comprise (by weight): at most 0.8 % iron, 0.2-0.6 % manganese, at most 0.4 % rare earth metals, 0.005-0.04 % strontium, at most 0.5 % zinc and at most 0.2 % titanium. The alloy can be high pressure die cast to form vehicle components such as engine components, wheels, steering wheels, steering columns, frame members, gear boxes, powertrain components, chassis components, body components and transmission systems. The alloy can have a yield strength of more than 200 MPa, an ultimate tensile strength of more than 350 MPa and an elongation of more than 5 % in an as-cast condition.

Description

AN ALUMINIUM ALLOY FOR HIGH PRESSURE DIE CASTING

TECHNICAL FIELD

The present disclosure relates to an alloy and particularly, but not exclusively, to aluminium casting alloys for use in castings of structural components. Aspects of the invention relate to an alloy composition, and to a method of making and using such alloys.

BACKGROUND

In the past several decades, the applications of lightweight materials in particular in automotive and aerospace industry have been the driving force to develop structural components produced by casting methods from aluminium alloys. Aluminium is favoured for the production of such components due to its ease of handling, its low cost, its ease of machinability and castability, and because it is relatively lightweight. Castings typically comprise complex geometries including parts that are exposed to elevated temperatures and pressures.

Aluminium-silicon, aluminium-silicon-copper and aluminium-magnesium-silicon systems have been established in the art. However, previous alloys only exhibit the required mechanical properties i.e. high yield strengths, tensile strengths and elongations when heat treated.

EP0918095 A1 for example discloses a structural component made of an alloy, consisting of (wt%) Si<0.5, Fed.O, Mn 0.1-1.6, Mg<5.0, Ti<0.3, Zn<0.1, Sc 0.05-0.4, optionally Zr 0.1-0.4 and the balance being aluminium. After a heat treatment at a temperature from 230 to 350 C, the castings show a yield strength of 120 MPa, a tensile strength of 180 MPa and an elongation of 16%.

Further, EP0918096 A1 discloses a die-cast aluminium alloy, consisting of (wt%) Si<1.4, Fe<0.8, Mn 0.1-1.6, Mg<5.0, Ti<0.2, Zn<0.1, V 0.05-0.3 and the balance being aluminium and impurities. After a heat treatment at a temperature from 200 to 400 “C, the die-casting can provide a yield strength of 120 MPa, a tensile strength of more than 180 MPa and an elongation more than 10%.

US 9322086 discloses an aluminium alloy for cast components comprising (wt%) Si 9-11.5, Mn 0.45-0.8, Mg 0.2-1.0, Cu 0.15-0.5, Zn 0.07-0.2, Zr 0.13-0.4, Cr<0.4, Mo 0.08-0.3, Fe 0.1-0.2, Ti 0.08-0.15, Sr 0.01-0.02 and the balance being aluminium and production-related impurities up to a total of not more than 0.5. The aluminium alloy component exhibits a yield strength of more than 120 MPa and an elongation of more than 7% which increases after heat treatment to a yield strength of more than 200 MPa and an elongation of more than 9%.

However, the existing aluminium alloys are mainly based on aluminium-silicon, aluminiumsilicon-copper and aluminium-magnesium-silicon systems and have difficulties satisfying the increased demands of manufacturing structural components with excellent mechanical properties i.e. yield strengths of more than 200 MPa and elongations of more than 4% without the need of a cost intensive heat treatment step. It is further highly desirable to produce an alloy with a high tolerance for iron and zinc as this allows the cost effective use of recycled materials.

A further problem with aluminium-silicon alloys for use in die castings is controlling the iron content. Iron represents an impurity due to the fact that it forms inter-metallics within the microstructure of the alloy that can lead to weakening, increased vulnerability to fatigue and reduced ductility. It is preferred, therefore, that the iron content in aluminium-silicon alloys is maintained at as low a level as possible. Consequently, such requirements discourage the use of recycled materials as a source of aluminium for die castings, so-called secondary alloys, because the contaminating iron content is typically too high. Hence, there is dependence in the art upon more costly primary alloys that are manufactured from pure iron-free aluminium that is alloyed with silicon and other additive elements to improve its mechanical properties.

The present invention provides alloy compositions and methods that meet the aforementioned objectives. These and other uses, features and advantages of the invention should be apparent to those skilled in the art from the teachings provided herein.

SUMMARY OF THE INVENTION

Against this background, the invention resides in a first aspect in an aluminium alloy composition comprising: at least about 7.5 wt% and at most about 12.5 wt% silicon, at least about 2.0 wt% and at most about 5.5 wt% copper, and at least about 0.3 wt%, and at most about 1.6 wt% magnesium.

In embodiments, the aluminium alloy may further comprise at most about 0.8 wt% iron.

According to another embodiment, the aluminium alloy may further comprise at least about 0.2 wt% and at most about 0.6 wt% manganese.

According to a further embodiment, the aluminium alloy may comprise a manganese/iron ratio of at least 0.5.

In embodiments, the aluminium alloy may further comprise at most about 0.4 wt% rare earth metals selected from one or more of the group consisting of: lanthanum; cerium; neodymium; yttrium; ytterbium; erbium and gadolinium.

According to a further embodiment, the aluminium alloy may further comprise at least about 0.005 wt% and most about 0.04 wt% strontium.

According to another embodiment, the aluminium alloy may further comprise at most about 0.5 wt% zinc.

In embodiments, the aluminium alloy composition may comprise at least about 7.8 wt% and at most about 10 wt% silicon, at least about 2.5 wt% and at most about 4.5 wt% copper, at least about 0.4 wt% and at most about 1.0 wt% magnesium, further comprising: at least about 0.25 wt% and at most about 0.5 wt% manganese, at most about 0.7 wt% iron, at most about 0.5 wt% zinc, at most about 0.007-0.02 wt% strontium; and at most about 0.3 wt% rare earth metals.

According to a further embodiment, the aluminium alloy composition may comprise at least about 8.0 wt% and at most about 9.5 wt% silicon, at least about 3.0 wt% and at most about 4.0 wt% copper, at least about 0.5 wt% and at most about 0.8 wt% magnesium, at least about 0.3 wt% and at most about 0.4 wt% manganese, at most about 0.6 wt% iron, at most about 0.5 wt% zinc, at most about 0.007 wt%-0.03 wt% strontium, and at most about 0.3 wt% rare earth metals.

According to another embodiment, the aluminium alloy composition may further comprise at most about 0.2 wt% titanium.

According to a further embodiment, the aluminium alloy composition as described above may be used in the manufacture of a high pressure die cast product.

According to another aspect of the herein presented invention, there is provided a cast product comprising the aluminium alloy as described.

According to a further embodiment, there is provided a cast product in the as-cast condition, which may have a yield strength of more than 200 MPa, an ultimate tensile strength of more than 350 MPa and an elongation of more than 5%.

According to another embodiment, there is provided a cast product wherein the cast product may be a vehicle component, optionally selected from one or more of the group consisting of: an engine component; a vehicle wheel; a steering wheel; a steering column; a frame member; a gear box; a powertrain component; a chassis component; a body component and a transmission system.

According to a further aspect, there is provided a vehicle comprising the cast product as described above.

According to a further embodiment the vehicle may be selected from the group consisting of: an automobile; a motorcycle; a locomotive; a watercraft and an aircraft.

According to a further aspect, there is provided a process for manufacturing a cast product, the process comprising casting an aluminium alloy as described above into a mould or die that defines the cast product.

According to a further embodiment, there is provided the process as described above, wherein the cast product may be manufactured by die casting.

According to a further embodiment, there is provided the process as described above, wherein the cast product is manufactured by high-pressure die casting.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a flow chart showing the cast product manufacturing process.

Figure 2 is a drawing of a vehicle comprising a cast product.

Figure 3 is a graph displaying the mechanical properties of machined samples from as-cast castings of alloy B at 120 “C.

Figure 4 is a graph displaying the mechanical properties of machined samples from as-cast castings of alloy B at 150 “C.

DETAILED DESCRIPTION

Unless otherwise defined, 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.

Prior to setting forth the invention, a number of definitions are provided that will assist in the understanding of the invention.

As used herein, the term comprising means any of the recited elements are necessarily included and other elements may optionally be included as well. Consisting essentially of” means any recited elements are necessarily included, elements that would materially affect the basic and novel characteristics of the listed elements are excluded, and other elements may optionally be included. Consisting of” means that all elements other than those listed are excluded. Embodiments defined by each of these terms are within the scope of this invention.

The term “alloy” is used herein to denote a metallic composition comprising a mixture of a predominating metallic element and other elements, including impurities. A basic aluminiumsilicon (Al-Si) alloy forms a simple eutectic system, with around 12 weight% (wt%) silicon being the eutectic composition at 577 °C.

“Casting” is a manufacturing process that can produce metal components through the use of moulds. In some instances the mould may be sacrificial, as in the case of gravity casting where a sand-mould is used, or the mould may take the form of a reusable die, such as may be used in high pressure die casting processes. The casting process involves a furnace, metal and the mould. Alternatively, a casting machine may also be used to apply pressure to the mould or die during the casting process. The metal, typically a non-ferrous alloy comprising aluminium, is first melted in the furnace and then poured or injected, optionally under pressure, into the mould. Once the casting has cooled and has set the part can be subjected to additional tooling or trimmed and finished. The cutting of the cast metal product is also known as machining. Casting processes can produce large and small component parts, with geometrically complex shapes. The cast parts are typically of high strength and can be subjected to considerable loads when in use. The process supports a reasonably high rate of production and is favoured producing consistent parts with good surface finish.

As mentioned, components manufactured via die casting processes of the present invention are also referred to as ‘parts’ and broadly refer to any metal object manufactured via the casting process. The parts are often comprised of geometrically complex shapes that perform a defined function. Components manufactured according to the present invention are particularly suitable for use in motor vehicles, locomotives, static engines, watercraft (marine) and aircraft.

As used herein, the term “balance”, when used in reference to a particular element, is used to describe that the remainder of the composition (in wt%) excluding any alloying additions is comprised of the designated element. Hence, the total composition including the “balance” element in combination with other stated alloying elements is equal to 100 wt% of the alloy composition. The term “impurity” refers to a metallic or non-metallic element that is present in an alloy but which is not added intentionally. In embodiments of the present invention where only specific component elements are specified, the balance of the alloy may comprise aluminium.

As used herein, the phrase “rare earth metal”, is used to describe one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Promethium may be excluded, in certain embodiments, due to its radioactive properties.

The term “mould”, as used herein, is referring to a hollow container used to give shape to molten or hot liquid material when it cools and hardens.

The term “die”, as used herein, is referring to a block with a special shape or with a pattern cut into it that is used for shaping pieces of metal.

The phrase “cast product” is used herein to denote an entity that has been cast in metal from a die or a mould.

The term “as-cast” is used herein to refer to a casting in the condition in which it comes out of the foundry, before any work-hardening or additional heat treatment is carried out.

As used herein, the term “vehicle” is used to denote any means in or by which people, animals or goods are transported or conveyed. Typically, vehicles may include road transport motor vehicles as well as rail locomotives. Watercraft may include marine vessels, such as boats, ships, submarines and hovercraft. Aircraft may include fixed wing or non-fixed wing aircraft, as well as spacecraft.

As mentioned the casting processes can produce large and small cast products also referred to as component parts. The term “vehicle component” is referring to any part that is deployed in a vehicle.

Turning now to the alloy of a specific embodiment of the invention, an aluminium alloy has a composition that comprises:

at least about 7.5 wt% and at most about 12.5 wt% silicon, at least about 2.0 wt% and at most about 5.5 wt% copper and at least about 0.3 wt% and at most about 1.6 wt% magnesium. The alloy may be used to manufacture structural components able to maintain their mechanical properties at elevated temperatures up to at least about 150 “C. Without wishing to be bound by theory, the present inventors have found that the balance between the elements allows for some components to dissolve in others and also gives rise to certain precipitates in the microstructure that provide an advantageous and unexpected benefit of high strength at both low and high temperatures.

In a specific embodiment the aluminium alloy has a composition that comprises:

at least about 7.5 wt% and at most about 12.5 wt% silicon, at least about 2.0 wt% and at most about 5.5 wt% copper and at least about 0.3 wt% and at most about 1.6 wt% magnesium and the balance comprising aluminium.

Silicon is present in the alloy of the herein presented invention at an amount of at least about 7.5 wt%, or suitably about 7.8 wt%, or typically about 8.0 wt%; and suitably at most about 9.5 wt%, or typically about 10 wt%, or optionally up to about 12.5 wt%. Silicon, as the primary alloying element in the present alloy, is able to decrease the liquid line to ensure a good castability. In embodiments of the invention, silicon forms an aluminium-silicon eutectic microstructure and combines with copper and magnesium to form AISiCuMg and AlSiCu phases to strengthen the alloy.

Copper is present in the alloy of the herein presented invention at an amount of at least about 2.0 wt%, or typically about 2.5 wt%, or suitably about 3.0 wt%; and suitably at most about 4.0 wt%, or typically about 4.5 wt%, or optionally up to about 5.5 wt%. According to embodiments of the invention, copper forms AI₂Cu, AlSiCu and AISiCuMg eutectic phases to strengthen the alloy. Some copper atoms may also dissolve in the solid α-aluminium matrix which has a solid solution strengthening effect and following precipitation a strengthening effect.

Magnesium is present in the alloy of the herein presented invention at an amount of at least about 0.3 wt%, or typically about 0.4 wt%, or suitably about 0.5 wt%; and typically at most about 0.8 wt%, or suitably about 1.0 wt%, or optionally up to about 1.6 wt%. In embodiments of the present invention. Magnesium forms AISiCuMg eutectics and particularly the AIMg and Mg₂Si phases strengthen the alloy. The presence of Mg in the alloy composition in the specified content may also allow some magnesium atoms to dissolve in solid aluminium which results in a solid solution strengthening effect and following precipitation strengthening effect.

The alloy may include further optional alloying elements as set out in specific embodiments, as will now be described.

In particular embodiments, the alloy includes one or more of the following elements.

Manganese at an amount of at least about 0.2 wt%, or typically about 0.25 wt%, or suitably about 0.3 wt%; and suitably at most about 0.4 wt%, or typically about 0.5 wt%, or optionally about 0.6 wt%. Manganese may be added to combine with iron to alter the morphology of ironcontaining compounds from needles to nodular which may mitigate any negative effects of iron within the alloy. The addition of manganese may also help to prevent die soldering and can contribute to the strength enhancement in the alloy. In a specific embodiment of the invention the amount of manganese present in the alloy is directly linked to the amount of iron in the alloy i.e. suitably a manganese/iron ratio of at least about 0.5.

The alloy may further comprises zinc as inevitable impurity - for example if the alloy contains recycled material - with at least about 0.001 wt%, or about 0.05 wt%, or about 0.10 wt%, or about 0.15 wt%; and with at most about 0.2 wt%, or about 0.3 wt%, or about 0.4 wt%, or about up to 0.5 wt%. It is highly desirable to incorporate a high level of tolerance to zinc in the aluminium alloy whilst maintaining the mechanical properties as this allows the cost effective use of recycled materials.

The alloy may further comprises iron as inevitable impurity - for example if the alloy contains recycled material - with at least about 0.001 wt%, or about 0.1 wt%, or about 0.2 wt% and at most about 0.3 wt%, or about 0.4 wt%, or about 0.5 wt%, or about 0.6 wt%, or about 0.7 wt%, or about up to 0.8 wt%. Iron can prevent die soldering and improve the strength of the alloy. Conventionally, the iron content is minimised, since its presence results in an iron-containing intermetallic phase that forms within an inter-dendritic region of the microstructure and that can lead to weakening, increased vulnerability to fatigue and reduced ductility. In particular, ironcontaining intermetallic phase particles tend to adopt the ‘script’ morphology, which is detrimental to the properties of the alloy because it contributes to the fracture mechanism, reducing strength and also bringing about an increase in porosity. However, surprisingly a high iron tolerance level whilst maintaining mechanical properties as demonstrated by the herein presented alloys is desirable since it allows for the use of recycled materials which reduces manufacturing costs and represents an environmentally friendly solution.

Hence, the present invention provides the unexpected technical advantage of relatively high tolerance to iron and zinc content without loss of important beneficial properties of the herein described alloys.

The alloy may further comprises titanium with suitably at least about 0.001 wt%, or typically about 0.025wt%, or optionally about 0.05 wt%; and typically at most about or 0.1 wt%, or suitably about 0.15 wt% or optionally about 0.2, or even up to about 0.25 wt%. In embodiments of the invention, titanium can refine primary aluminium grains and therefore increase both the strength and elongation of the alloys.

Strontium may be present in the alloy of the herein presented invention with at least about 0.005 wt%, or optionally about 0.007 wt% and typically with at most about 0.02 wt%, or suitably about 0.03 wt%, or optionally about 0.04 wt%. In embodiments of the invention strontium is used as a modifying element of the silicon phase.

The alloy may further comprise one or more rare earth elements at an amount of about 0.001 wt%, or about 0.025 wt%, or 0.5 wt% and at most about 0.1 wt%, or about 0.2 wt%, or about 0.3 wt%, or optionally up to about 0.4 wt%. In embodiments of the invention, rare earth metals provide modification of the iron and silicon phase, and may enhance the grain refining effect of titanium, if present. Therefore, the aluminium alloy may also include small amounts of one or more other rare earth elements including lanthanum, cerium, neodymium, yttrium, ytterbium, erbium and gadolinium. In particular embodiments, lanthanum and cerium are selected because they may be less expensive than other rare earth elements and usually exist in mixtures. Further, the rare earth elements, in particular lanthanum and cerium, may be added to the alloy for better ductility of the cast product.

An example of an alloy according to one embodiment of the invention is provided as set out below:

The aluminium alloy comprising at least about 8.0 wt% and at most about 9.5 wt% silicon, at least about 3.0 wt% and at most about 4.0 wt% copper, at least about 0.5 wt% and at most about 0.8 wt% magnesium, at least about 0.3 wt% and at most about 0.4 wt% manganese, at most about 0.6 wt% iron, at most about 0.5 wt% zinc, at least about 0.007 wt% and at most about 0.03 wt% strontium, and at most about 0.3 wt% rare earth metals.

In a specific embodiment there is provided an alloy composition that comprises: at least about 7.5 wt% and at most about 12.5 wt% silicon, at least about 2.0 wt% and at most about 5.5 wt% copper, at least about 0.3 wt% and at most about 1.6 wt% magnesium, at least about 0.2 wt% and at most about 0.6 wt% manganese, at most about 0.5 wt% zinc, at most about 0.2 wt% titanium, at most about 0.8 wt% iron, at least about 0.007 wt% and at most about 0.04 wt% strontium and at most about 0.4 wt% rare earth metals, wherein the die-cast product in the ascast condition has a yield strength more than 200 MPa, a ultimate tensile strength more than 350 MPa and an elongation more than 5%.

An example of a method of producing a cast product and a cast component using the casting alloy will now be described. The die block which is usually covered in a water-based die releasing lubricant is preheated using the circulation of mineral oil at about 250 “C. The melted alloy composition 30 shown in Figure 1 having the components as described above is usually injected at a temperature of about 650 “C at an injection speed of about 50 m/s. Immediately after the die cast ‘shot’ an intensification pressure of about 320 bar is applied to reduce gas and shrinkage porosity. After a cooling period of about 48 hours the cast product 20 may be worked up for use or subjected to mechanical testing.

The as-cast alloys of the present invention, once cast, exhibit a high strength at both ambient temperatures and at high temperatures (for example, temperatures above 150 °C). These beneficial mechanical properties at both high and ambient temperatures make the cast component ideally suited for vehicle applications. In a particular embodiment of the invention the die-cast product in the as-cast condition demonstrates a yield strength more than 200MPa, an ultimate tensile strength (UTS) of more than 350MPa and an elongation more than 5%.

The mechanical parameters, namely yield strength, the ultimate tensile strength and elongation are determined using the American Society for Testing and Materials (ASTM) standard B557. ASTM B557 is a testing standard that covers the tension testing requirements of wrought and cast aluminium- and magnesium-alloy products. Other organisations proving standards for such testing, which are met by the present invention, are the Society of Automotive Engineers (SAE), the Japan Standards Association (JIS), the Deutsche Institut fiir Normung (DIN), the European Committee for Standardisation (EN) and the International Organisation for Standards (ISO).

The vehicle in which the cast component 20 is deployed may be an automobile 10 shown in Figure 2; a motorcycle; a locomotive; a watercraft or an aircraft. The cast component itself may be an engine component; a vehicle wheel; a steering wheel; a steering column; a frame member; a gear box, a powertrain component, a chassis component, a body component and transmission system. It will be appreciated that the aforementioned list of vehicles and the aforementioned list of components are not intended to be exhaustive, and other vehicles and/or components are contemplated.

The invention is further illustrated by the following non-limiting examples.

Example 1

An industrial scale of Freeh 450-54 cold chamber high pressure die casting machine with a locking pressure of 4500 kN was used to cast a standard cast product. The casting die was preheated using the circulation of mineral oil at 250 “C. The pouring temperature is usually at 650 “C measured by a K-type thermocouple. An especially designed die was used to cast three ASTM standard round samples with a diameter of 6.35 mm.

During casting, the injection speed was controlled at 3.5 m/s for the piston, which corresponds to the in-gate speed at a level of 50 m/s. The intensification pressure was at 320 bar. A waterbased die releasing lubricant was used on the die block. All casting samples were left for at least 48 hour before testing their mechanical properties. The tensile tests were conducted following ASTM standard B557, using an Instron 5500 Universal Electromechanical Testing System equipped with Bluehill control software and a 50 kN load cell. All tensile tests were performed at an ambient temperature (20 °C). The gauge length of the extensor meter was 25 mm. The composition of alloys and the mechanical properties in the as-cast condition have been listed in Table 1 and Table 2, respectively. The alloy according to the invention showed no tendency to die-sticking during the die-casting operation.

Table 1 Chemical composition of the alloys.

Alloy Si Cu Mg Fe Mn Zn Ti Sr Re Al

101 8 3.0 0.5 0.6 0.4 0.16 0.14 0.015 0 Bal.

102	8	3.0	0.5	0.6	0.4	0.15	0.14	0.015	0.20	Bal
103	8	3.5	0.6	0.6	0.4	0.17	0.14	0.015	0.30	Bal
104	8	3.9	0.7	0.6	0.4	0.20	0.14	0.015	0.10	Bal
105	8	3.9	0.7	0.6	0.4	0.16	0.14	0.015	0	Bal
106	8	4.2	0.8	0.3	0.3	0.21	0.14	0.015	0	Bal
107	8.5	3.0	0.6	0.6	0.4	0.17	0.14	0.015	0	Bal
108	8.5	3.0	0.7	0.6	0.4	0.15	0.13	0.015	0.15	Bal
109	8.5	3.5	0.7	0.6	0.4	0.18	0.14	0.015	0.25	Bal
110	8.5	3.9	0.7	0.6	0.4	0.18	0.14	0.015	0	Bal
111	8.5	4.1	0.6	0.5	0.3	0.18	0.16	0.015	0	Bal
112	8.5	4.5	0.5	0.4	0.4	0.18	0.18	0.020	0	Bal
113	9.5	3.6	0.6	0.6	0.4	0.17	0.15	0.019	0	Bal
114	9.5	4.0	0.5	0.5	0.4	0.13	0.12	0.020	0	Bal
115	9.5	4.5	0.5	0.4	0.4	0.10	0.18	0.020	0.12	Bal
116	10.1	3.3	0.7	0.6	0.4	0.12	0.18	0.020	0	Bal
117	10.1	3.9	0.5	0.6	0.4	0.10	0.20	0.230	0.10	Bal
118	10.1	4.2	0.5	0.5	0.4	0.15	0.19	0.250	0.16	Bal
119	10.1	4.5	0.5	0.3	0.3	0.15	0.19	0.280	0.24	Bal
A380	8.5	3.5	0.1	0.9	0.5	1.80	0.14	0.015	0	Bal
LM24	8.5	3.5	0.15	0.9	0.5	1.80	0.14	0.015	0	Bal

The results presented in table 1 and table 2 relating to the aluminium alloy composition according to the present invention show an improvement of tensile properties in comparison with the commercially available LM24 and A380 standards under as-cast condition. These excellent properties are achieved without the need for further heat treatments. In particular, the yield strength can be improved by increasing the contents of copper and magnesium. Smaller improvements in yield strength can be obtained by increasing the silicon contents. The addition of rare earth metals can also improve the elongation of the alloy under as-cast condition.

Table 2 Mechanical properties of the high pressure die-casting alloys.

Alloy	Yield strength (MPa)	UTS (MPa)	Elongation (%)
101	202	353	5.96
I02	207	358	6.34
I03	214	362	5.85
I04	217	365	5.70
I05	215	359	5.50
I06	221	364	5.67
I07	208	359	5.76
I08	212	359	5.79
I09	224	368	5.80
110	220	364	5.49
111	218	362	5.54
112	222	369	5.29
113	226	367	5.74
114	220	358	5.64
115	225	362	5.81
116	229	364	5.75
117	226	360	5.76
118	230	356	5.69
119	229	354	5.80
A380	146	319	4.15
LM24	143	320	3.92

Example 2

A cast component was produced by a Freeh 450-54 cold chamber high pressure die casting machine with a locking pressure of 4500kN. The typical wall thickness was 2.8 mm for the diecasting. The injection parameters were optimised for each type of casting and the castings were made under the corresponding optimised condition. The dies were heated by the circulation of mineral oil at 250 “C. The pouring temperature was at 650 “C measured by a K-type thermo15 couple. All casting samples were contained at ambient condition for at least 48 h before the mechanical properties were tested. 20 pieces of such castings were selected to produce tensile samples. 5 standard square samples with a cross section of 6.35x2.8 mm were machined from each casting at a fixed location. The compositions of the alloys were: A (wt%) AI-8.5Si-3.5Cu0.7Mg-0.6Fe-0.4Mn-0.2Zn-0.15Ti-0.015Sr and B (wt%) AI-8.5Si-3.5Cu-0.7Mg-0.6Fe-0.4Mn0.2Zn-0.15Ti-0.25Re-0.015Sr. The mechanical properties of machined as-cast samples at room temperature have been listed in Table 3. And the mechanical properties of machined as-cast samples (Alloy B, Position 2) at 120 °C and 150 °C are shown in Figures 3 and 4.

The results in Table 3 and Figures 3 and 4 show that machined samples as opposed to standard samples cut from different locations of casting maintain good mechanical properties

i.e. the yield strength is more than 200MPa, the tensile strength is more than 350MPa and elongation is more than 3%. This is particularly unexpected since different wall thicknesses, shapes and solidification parameters at different locations of the casting usually result in much lower parameters.

Table 3 Mechanical properties (room temperature) of the machined samples from the as-cast castings.

	Location	Position 1	Position 2	Position 3	Position 4	Position 5
	Elongation (%)	3.26	3.20	3.04	3.09	3.25
Alloy A	UTS (MPa)	327	342	338	338	349
	Yield strength (MPa)	210	207	213	210	205
	Elongation (%)	3.46	3.38	3.29	3.22	3.41
Alloy B	UTS (MPa)	353	362	358	360	356
	Yield strength (MPa)	219	216	221	215	210

Alternative expressions of the inventive concept are set out in each of the following clauses:

1. An aluminium alloy composition comprising:

at least about 7.5 wt% and at most about 12.5 wt% silicon, at least about 2.0 wt% and at most about 5.5 wt% copper, and at least about 0.3 wt%, and at most about 1.6 wt% magnesium.

2. The aluminium alloy composition of clause 1, further comprising at most about 0.8 wt% iron.

3. The aluminium alloy composition of clause 1 or clause 2, further comprising at least about 0.2 wt% and at most about 0.6 wt% manganese.

4. The aluminium alloy composition of clause 3, comprising a manganese/iron ratio of at least 0.5.

5. The aluminium alloy composition of any one of the preceding clauses, further comprising at most about 0.4 wt% rare earth metals selected from one or more of the group consisting of: lanthanum; cerium; neodymium; yttrium; ytterbium; erbium and gadolinium.

6. The aluminium alloy composition of any one of the preceding clauses, further comprising at least about 0.005 wt% and most about 0.04 wt% strontium.

7. The aluminium alloy composition of any one of the preceding clauses, further comprising at most about 0.5 wt% zinc.

8. The aluminium alloy composition of clause 1, wherein the alloy comprises:

at least about 7.8 wt% and at most about 10 wt% silicon, at least about 2.5 wt% and at most about 4.5 wt% copper, at least about 0.4 wt% and at most about 1.0 wt% magnesium, further comprising:

at least about 0.25 wt% and at most about 0.5 wt% manganese, at most about 0.7 wt% iron, at most about 0.5 wt% zinc, at most about 0.007-0.02 wt% strontium; and at most about 0.3 wt% rare earth metals.

9. The aluminium alloy composition of clause 8, wherein the alloy comprises:

at least about 8.0 wt% and at most about 9.5 wt% silicon, at least about 3.0 wt% and at most about 4.0 wt% copper, at least about 0.5 wt% and at most about 0.8 wt% magnesium, at least about 0.3 wt% and at most about 0.4 wt% manganese, at most about 0.6 wt% iron, at most about 0.5 wt% zinc, at most about 0.007 wt%-0.03 wt% strontium, and at most about 0.3 wt% rare earth metals.

10. The aluminium alloy composition of any one of the preceding clauses, further comprising at most about 0.2 wt% titanium.

11. The use of the aluminium alloy composition as described in any one of clauses 1 to 10 for the manufacture of a high pressure die cast product.

12. A cast product comprising the aluminium alloy of any one of clauses 1 to 10.

13. The cast product of clause 12, wherein the cast product in the as-cast condition has a yield strength of more than 200 MPa, an ultimate tensile strength of more than 350 MPa and an elongation of more than 5%.

14. The cast product of clauses 12 or 13 wherein the cast product is a vehicle component, optionally selected from one or more of the group consisting of: an engine component; a vehicle wheel; a steering wheel; a steering column; a frame member; and a gear box; a powertrain component; a chassis component; a body component and a transmission system.

15. A vehicle comprising the cast product of clauses 12, 13 or 14.

16. The vehicle of clause 15 selected from the group consisting of: an automobile; a motorcycle; a locomotive; a watercraft and an aircraft.

17. A process for manufacturing a cast product, comprising casting an aluminium alloy of any one of clauses 1 to 10 into a mould or die that defines the cast product.

18. The process of clause 17, wherein the cast product is manufactured by die casting.

19. The process of clause 18, wherein the cast product is manufactured by high-pressure die casting.

Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims, which follow. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.

Claims

AN ALUMINIUM ALLOY FOR HIGH PRESSURE DIE CASTING CLAIMS

1. An aluminium alloy composition comprising:

2. The aluminium alloy composition of claim 1, further comprising at most about 0.8 wt% iron.

3. The aluminium alloy composition of claim 1 or claim 2, further comprising at least about 0.2 wt% and at most about 0.6 wt% manganese.

4. The aluminium alloy composition of claim 3, comprising a manganese/iron ratio of at least 0.5.

5. The aluminium alloy composition of any one of the preceding claims, further comprising at most about 0.4 wt% rare earth metals selected from one or more of the group consisting of: lanthanum; cerium; neodymium; yttrium; ytterbium; erbium and gadolinium.

6. The aluminium alloy composition of any one of the preceding claims, further comprising at least about 0.005 wt% and most about 0.04 wt% strontium.

7. The aluminium alloy composition of any one of the preceding claims, further comprising at most about 0.5 wt% zinc.

8. The aluminium alloy composition of claim 1, wherein the alloy comprises:

9. The aluminium alloy composition of claim 8, wherein the alloy comprises:

10. The aluminium alloy composition of any one of the preceding claims, further comprising at most about 0.2 wt% titanium.

11. The use of the aluminium alloy composition as described in any one of claims 1 to 10 for the manufacture of a high pressure die cast product.

12. A cast product comprising the aluminium alloy of any one of claims 1 to 10.

13. The cast product of claim 12, wherein the cast product in the as-cast condition has a yield strength of more than 200 MPa, an ultimate tensile strength of more than 350 MPa and an elongation of more than 5%.

14. The cast product of claims 12 or 13 wherein the cast product is a vehicle component, optionally selected from one or more of the group consisting of: an engine component; a vehicle wheel; a steering wheel; a steering column; a frame member; and a gear box; a powertrain component; a chassis component; a body component and a transmission system.

15. A vehicle comprising the cast product of claims 12, 13 or 14.

16. The vehicle of claim 15 selected from the group consisting of: an automobile; a motorcycle; a locomotive; a watercraft and an aircraft.

17. A process for manufacturing a cast product, comprising casting an aluminium alloy of any one of claims 1 to 10 into a mould or die that defines the cast product.

18. The process of claim 17, wherein the cast product is manufactured by die casting.

19. The process of claim 18, wherein the cast product is manufactured by high-pressure die casting.