WO2020018477A1

WO2020018477A1 - Aluminum casting alloys

Info

Publication number: WO2020018477A1
Application number: PCT/US2019/041912
Authority: WO
Inventors: Randy S. BEALS
Original assignee: Magna International Inc
Current assignee: Magna International Inc
Priority date: 2018-07-16
Filing date: 2019-07-16
Publication date: 2020-01-23
Anticipated expiration: 2021-01-16

Abstract

An aluminum alloy comprising high amounts of manganese and/or strontium, and method of production of a cast part formed of the aluminum alloy in a direct chill counter pressure permanent mold casting system, is provided. In addition to the increased manganese and/or strontium, the aluminum alloy also contains silicon, iron, copper, magnesium, zinc, and aluminum. The casting system includes a mold defining a plurality of pores sized to allow quench media to enter the mold to cool the molten aluminum alloy contained therein without allowing the molten aluminum alloy to seep into the pores and out of the mold. The increased levels of manganese and/or strontium allows the molten aluminum alloy to be placed within the mold, solidified, and cleanly removed without having to add a releasing agent to the mold.

Description

ALUMINUM CASTING ALLOYS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This PCT International Patent Application claims the benefit of and priority to

U.S. Provisional Patent Application No. 62/698,564 filed July 16, 2018, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0002] The present invention relates to an aluminum alloy, a casting formed of the aluminum alloy, and a method of casting a structural component formed of the aluminum alloy for an automotive vehicle.

2. Related Art

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Casting is a popular production process wherein molten material is poured into a cavity and allowed to cool and solidify into a useful article. These useful articles can range from modest household goods to complex automotive parts. Like the large variety of articles produced from casting, the molten material used therein ranges from an assortment of metals, plastics, plasters, and concretes. Like all other forms of large-scale production, efficiency is one of the major goals in the casting process. During the casting process, the molten material is stored in a holding furnace and poured into a solid steel mold (usually H13 or P20 tool steel) from an injection machine where it remains until it cools enough to solidify into a casting. The time it takes molten material to be introduced into the mold, allowed solidify into a casting, and ejected is called a casting cycle.

[0005] In order to cleanly remove the casting from the mold, a releasing agent is applied in a layer onto an interior surface of the mold that contacts the molten material. This layer of releasing agent is called a“mold coating or mold paint coating.” In regard to the high pressure die casting, the release agent is the die lube that is applied after each and every cycle of the machine. The releasing agent forms a matrix between the molten material and the mold, preventing bonding therebetween, to facilitate removal of the casting after the molten material has solidified. After the casting is ejected, additional releasing agent is applied to the mold to form additional castings. While the releasing agent is effective at preventing bonding, it is an additional step that must be carried out correctly. In other words, if the releasing agent is not applied such that it coats the entire inside of the mold, then parts of the casting can stick to the mold and tear or deform upon removal to create surface irregularities. In addition, the inner mold surface must be scrubbed and dried between applications to prevent any disturbance from rust, dirt, or other impurities. While some releasing agents can be used for more than one cycle, the time it takes to apply the releasing agent can be substantial, ultimately being labor intensive and requiring onsite space to hold the releasing agent as it cannot be reused. Moreover, releasing agents are often times hazardous to the environment and operators and thus must be shipped, stored, and used according certain regulations.

[0006] Another problem is that the casting cycles are bottlenecked by the speed at which it takes the molten material to cool within the mold. Conventional cooling of the molten material typically occurs in two discrete thermal transfer phases, convection followed by radiation. During the convection phase, the mold is cooled causing the molten material therein to constrict away from sides of the mold. After constriction, the molten material is no longer in direct contact with the cooled mold and thus enters the second phase of cooling, radiation. The radiation phase slows the casting cycle and creates larger dendridic arm spacing (DAS), resulting in lower mechanical properties. In addition to reduced efficiency, slower casting cycles place limits on the molten materials that can be used in preparation of castings.

[0007] As such, there is a continuing desire to increase the casting cycle efficiencies and retain high production rates of quality castings with improved mechanical properties such as a reduction to weight and an increase in strength.

SUMMARY OF THE INVENTION

[0008] The subject invention provides an aluminum alloy for a direct chill counter pressure permanent mold casting system and a casting formed of the aluminum alloy. The aluminum alloy includes, in weight percent (wt.%) based on total weight of the alloy, manganese in an amount up to 1.8 wt.%, silicon in an amount of 0.1 wt.% to 7.5 wt.%, iron in an amount of 0.12 wt.% to 1.0 wt.%, copper in an amount of 0.05 wt.% to 5.0 wt.%, magnesium in an amount of 0.1 wt.% to 5.0 wt.%, zinc in an amount of 0.05 wt.% to 6.1 wt.%, strontium in an amount up to 0.06 wt.%, other elements each in an amount up to 0.05 wt.%, the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum.

[0009] The subject invention also provides a method of casting a structural component for an automotive vehicle, comprising the steps of: filling a casting chamber defined by a mold with an aluminum alloy while the aluminum alloy is molten, wherein the aluminum alloy comprises manganese in an amount up to 1.8 wt.%, silicon in an amount of 0.1 wt.% to 7.5 wt.%, iron in an amount of 0.12 wt.% to 1.0 wt.%, copper in an amount of 0.05 wt.% to 5.0 wt.%, magnesium in an amount of 0.1 wt.% to 5.0 wt.%, zinc in an amount of 0.05 wt.% to 6.1 wt.%, strontium in an amount up to 0.06 wt.%, other elements each in an amount up to 0.05 wt.%, the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum. For example, the aluminum alloy can be used in a gas quenching or water quenching direct chill counter pressure permanent mold casting system. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure will be more readily understood by reference to the following description in combination with the accompanying drawings wherein:

[0011] FIG. 1 is a cross-sectional view of a direct chill counter pressure permanent mold casting system (DCCPPM);

[0012] FIG. 2A illustrates a conventional cooling system in a radiation heat transfer stage and FIG. 2B illustrates the direct chill counter pressure permanent mold casting system directly applying quench media during convection heat transfer;

[0013] FIG. 3 is a microscopic view of a mold having a plurality of pores allowing the permanent mold to be permeable;

[0014] FIG. 4 is a perspective view of parts constructed in accordance to the subject method;

[0015] FIG. 5A is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating a releasing agent being applied to the mold with an applicator, which becomes unnecessary after an aluminum alloy with at least 1.2 wt.% manganese and/or 0.04 wt.% to 0.06 wt.% of strontium is used;

[0016] FIG. 5B is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating pre-heating of the mold with a pre-heating element;

[0017] FIG. 5C is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating a lift mechanism in a closed condition; [0018] FIG. 5D is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating compressed air being introduced to a furnace and pressurizing the furnace;

[0019] FIG. 5E is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating quench media being introduced to a cooling chamber containing the mold and pressurizing the cooling chamber;

[0020] FIG. 5F is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating a solidification process of the molten aluminum alloy as the cooling chamber and furnace are respectively pressurized;

[0021] FIG. 5G is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating a step of depressurizing the furnace and cooling chamber including recapturing the quench media;

[0022] FIG. 5H is a cross-sectional view of the direct chill counter pressure permanent mold casting system illustrating the solidified casted part formed from the molten aluminum alloy being ejected from the mold;

[0023] FIG. 6 graphically represents a casting cycle in pressure as a function of time utilizing Ar and/or helium as a quench media as illustrated in of the casting system shown in FIGS. 5D through 5G;

[0024] FIG. 7 graphically represents a casting cycle of another embodiment using direct chill counter pressure with water used as the quench media with a casting rotary table;

[0025] FIG. 8 graphically represents a cooling rate of molten aluminum material as a function of secondary dendritic arm spacing;

[0026] FIG. 9 charts a non-exhaustive list of molten materials and a comparison of their material properties that can be used in accordance with the present invention; [0027] FIG. 10 charts a comparison of aluminum cooling cycles between He and N2 gas being introduced as quench media and cooling the molten material from 950F to 400F under various pressure loads;

[0028] FIG. 11 charts a comparison of sand cast aluminum (A356) cooling cycles between air, Ar, and He being introduced as quench media;

[0029] FIGS. 12A, 12B and 12C are tables illustrating different compositions of aluminum alloy in accordance with the subject invention wherein FIG. 12C illustrates the addition of Scandium and Zirconium; and

[0030] FIG. 13 illustrates the saving of time (in seconds) by eliminating the step of applying releasing agent as compared to the graph in FIG. 7.

DESCRIPTION OF THE ENABLING EMBODIMENT

[0031] Example embodiments will now be described more fully with reference to the accompanying drawings. In general, the subject embodiments are directed to an aluminum alloy for a direct chill counter pressure permanent mold casting system and a casted part produced by same. However, the example embodiments are only provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0032] Referring to the Figures, wherein like numerals indicate corresponding parts throughout the views, the aluminum casting alloy and associated direct chill counter pressure permanent mold casting system 20 is intended for reducing or eliminating the requirements of applying a releasing agent and producing casted parts 40 (including parts 40’ and 40”) with improved material properties. As it will be appreciated with further reading, this reduction of cooling cycles allows for the production of castings using raw materials and molten aluminum alloys that have proven difficult in the past. Additions of Mn and Sr to these materials, that have proven difficult to work with in the past further, allow the produced castings to be cleanly removed from a die without a releasing agent. Moreover, the casted parts 40 produced from the aluminum alloy exhibit increased strength and increases in Young’s modulus (Metal Matrix Composite) and are thus particularly useful as structural components for automotive vehicles.

[0033] Looking first to the system 20, a cross-sectional view of the direct chill counter pressure permanent mold casting system 20 is shown in FIG. 1. The direct chill counter pressure permanent mold casting system 20 includes a molding assembly 22 and a furnace assembly 24. The molding assembly 22 includes a mold 26 disposed between a bottom plate 28 and a top plate 30. The mold 26 includes a upper mold part 32 and a lower mold part 34. The upper mold part 32 is attached to the top plate 30 and the lower mold part 34 is attached to the bottom plate 28. A lift mechanism 36, which preferably operates via hydraulic actuation, moves the bottom plate 28 axially towards and away from the top plate 30. The lift mechanism 36 includes a closed condition, wherein the upper mold part 32 and lower mold part 34 are sealingly brought together to form a casting chamber 38 for retention of molten aluminum alloy. The lift mechanism 36 further includes an open condition wherein the upper mold part 32 and lower mold part 34 are separated, such that a solidified molten aluminum alloy or casted part 40 can be removed.

[0034] A pressure vessel 42 is attached to the top plate 30 and extends downwardly towards the bottom plate 38 to a seal end 44. The seal end 44 of the pressure vessel 42 comes into sealing contact with the bottom plate 28 when the lift mechanism 36 is in the closed condition to impermeably surround the mold 26 and casting chamber 38 in a cooling chamber 46. An input port 48 is disposed through the pressure vessel 42 for selectively filling the cooling chamber 46 with quench media. The quench media can be gas or liquid, however, if the quench media is gas it is preferable that it be cooled air, helium, N2 or Ar. Still, it should be appreciated that the quench media can also be liquid without departing from the scope of the subject disclosure. As best illustrated in FIGS. 2B and 3, the mold 26 defines a plurality of pores 50 extending therethrough into the casting chamber 38. The pores 50 are approximately 7 to 20 microns in diameter and are sized to allow entry of the quench media into the casting chamber 38 without allowing seepage of the molten aluminum alloy out of the casting chamber 38. The mold 26 is preferably comprised of semi sintered steel alloy and more specifically (35/38 HRC) powder tool steel, non-hipped porous steel. When the media is exposed to the molten aluminum alloy, a release of gas or steam can be vacuumed out of the input port 48 or a separate output port not shown. To this extent, the output port includes a relief valve for exiting heated media upon a certain pressure threshold. In addition, this system allows the quench media to be recaptured and not released into the surrounding environment. To this extent, by recapturing the quench media, the casting system 20 provides much better working conditions and minimizes quench media losses by closed loop recycling. FIGS. 2A and 2B compare a conventional casting system to the direct chill counter pressure permanent mold casting system. FIG. 2A illustrates the conventional cooling system in a radiation heat transfer phase, and FIG. 2B illustrates the direct chill counter pressure permanent mold casting system directly applying quench media during the convection heat transfer phase.

[0035] Now referring back to FIG. 1, the furnace assembly 24 includes a furnace 52 for heating and maintaining the molten aluminum alloy. The furnace 52 has an interior chamber 54 containing a crucible 56 that holds the molten aluminum alloy and a pressure line 58 extends through the furnace 52 for pressurizing a fill stalk 60. The fill stalk 60 extends from the crucible 56 to an intermediate stalk tube 62 that extends through the bottom plate 28 of the mold assembly 22 to an insert tube 63 in the lower mold part 34. The fill stalk 60 transfers molten aluminum alloy from the crucible 56 when the pressure line 58 pressurizes at least the fill stalk 60 and urges the molten aluminum alloy upwards into the mold 26 when the lift mechanism 36 is in the closed condition and the mold 26 is sealed. A power supply 64 extends into the furnace 52 for supplying energy thereto.

[0036] FIG. 4 illustrates various parts 40’, 40” constructed in accordance with the subject method. In a preferred embodiment, the parts are utilized in an automobile. For example, these parts can include chassis components 40’ and sub-frame components 40”.

[0037] As shown in FIG. 5A, when conventional molten materials are utilized the direct chill counter pressure permanent mold casting system 20 further requires an applicator 98 for coating the inside of the casting chamber 38 with the releasing agent, facilitating removal of a casting upon solidification. However, in the direct chill system 20, the releasing agent can interfere with the pores 50 and make is difficult for quench media to enter the mold 26.

[0038] Referring now to FIG. 5B, the direct chill counter pressure permanent mold casting system 20 also includes a pre-heating element 100 that is applied to the mold 26 before injection of the molten aluminum alloy. The pre-heating element 100 includes an outer layer 102 that has a high emissivity for increased effectiveness in emitting thermal radiation and an inner layer 104 of thermally conductive material. In a preferred

embodiment, the outer layer 102 comprises graphite and the inner layer 104 comprises plasma. This pre-heating element 100 preheats the mold for improved initial disbursement of the molten aluminum alloy into the casting chamber 38. [0039] The application of quench media through the pores 50 of the mold 26 thus maintains a uniform contact with the solidifying molten aluminum alloy resulting in an accelerated heat loss. This uniform contact remedies past shortcoming of the conventional methods, namely the uniform contact persists through shrinkage of the molten aluminum alloy such that the cooling cycle does not experience the phase shift between convention heat transfer to the slower radiation heat transfer.

[0040] As mentioned above, this reduction in time of the cooling cycle further enables the ability to cast wrought materials, such as aluminum alloys, for example aluminum 6061. The aluminum alloys typically comprise, in weight percent (wt.%) based on the total weight of the alloy: silicon (minimum 0.4 wt.%, maximum 0.8 wt.%); iron (no minimum, maximum 0.7 wt.%); copper (minimum 0.15 wt.%, maximum 0.4 wt.%); manganese (no minimum, maximum 0.15 wt.%); magnesium (minimum 0.8 wt.%, maximum 1.2 wt.%); chromium (minimum 0.04 wt.%, maximum 0.35 wt.%); zinc (no minimum, maximum 0.25 wt.%); titanium (no minimum, maximum 0.15 wt.%); aluminum (minimum 95.85 wt.%, maximum 98.56 wt.%); and other elements. However, if the aluminum alloy 6061 or other aluminum alloys have a high amount of strontium (Sr), such as approximately 0.360 wt.% instead of the normal 0.015 to 0.025 wt.% found in some aluminum alloys and/or an increase of manganese (Mn), to a range between minimum 1.2 wt.%, maximum 1.8 wt.% then no release agent is necessary. The chill casting system 20 can be utilized in low-pressure casting or high-pressure casting and can also utilize sand cores, without any danger of their destruction even under varying pressures, for producing casted parts 40 with hollow cores.

[0041] Multiple example embodiments of aluminum alloy with increased levels of manganese are presented in Tables 1-3 below. These aluminum alloys include, in weight percent (wt.%) based on total weight of the alloy, manganese in an amount up to 1.8 wt.%, silicon in an amount of 0.1 wt.% to 7.5 wt.%, iron in an amount of 0.12 wt.% to 1.0 wt.%, copper in an amount of 0.05 wt.% to 5.0 wt.%, magnesium in an amount of 0.1 wt.% to 5.0 wt.%, zinc in an amount of 0.05 wt.% to 6.1 wt.%, strontium in an amount up to 0.06 wt.% (600ppm), other elements each in an amount up to 0.05 wt.%, the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum. The other elements are optional and can include, for example, impurities.

[0042] According to example embodiments, the aluminum alloy includes manganese in an amount of 1.2 wt.% to 1.8 wt.%, silicon in an amount of 0.1 wt.% to 1.3 wt.%, iron in an amount of 0.15 wt.% to 1.0 wt.%, copper in an amount of 0.05 wt.% to 2.0 wt.%, magnesium in an amount of 0.1 wt.% to 2.9 wt.%, zinc in an amount of 0.1 wt.% to 0.25 wt.%, strontium in an amount up to 1.0 wt.%, other elements each in an amount up to 0.05 wt.%, the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum.

[0043] According to other example embodiments, the aluminum alloy includes silicon in an amount of 0.1 wt.% to 1.3 wt.%, iron in an amount of 0.15 wt.% to 0.95 wt.%, copper in an amount of 0.05 wt.% to 2.0 wt.%, magnesium in an amount of 0.15 wt.% to 2.9 wt.%, zinc in an amount of 0.1 wt.% to 3.0 wt.%, strontium in an amount of 0.02 wt.% to 0.04 wt.%, titanium in an amount up to 0.2 wt.%, chromium in an amount up to 0.25 wt.%, scandium in an amount up to 0.1 wt.%, zirconium in an amount up to 0.1 wt.%, other elements each in an amount up to 0.05 wt.%, the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum.

[0044] According to other example embodiments, the aluminum alloy includes manganese in an amount of 0.1 to 1.8 wt.%, silicon in an amount of 5.5 wt.% to 7.5 wt.%, iron in an amount of 0.12 wt.% to 1.0 wt.%, copper in an amount of 0.05 wt.% to 4.0 wt.%, magnesium in an amount of 0.1 wt.% to 0.6 wt.%, zinc in an amount of 0.05 wt.% to 3.0 wt.%, strontium in an amount of 0.04 wt.% (400ppm) to 0.06 wt.% (600ppm), other elements each in an amount up to 0.05 wt.%, the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum.

[0045] It should be appreciated that the afore-described direct chill counter pressure permanent mold casting system 20 includes a method of operation. Referring in order to FIGS. 5B through 5H, aluminum alloy containing high amounts of Sr and/or Mn as described above is melted in a furnace into a molten condition. The mold 26 is heated to a

predetermined temperature via thermal radiation from a pre-heating element 100. Next, the lift mechanism 36 is brought to a closed condition, sealing the mold 26 and sealing the pressure vessel 42 between the bottom plate 28 and the top plate 30 to enclose the cooling chamber 46. Once in a closed condition, the fill stalk 60 is pressurized with compressed air while the quench gas is simultaneous applied to the cooling chamber 46 allowing a controlled pressure differential such that the aluminum alloy can rise into the casting cavity at a controlled and tranquil rate. In a preferred embodiment, both the fill stalk 60 and cooling chamber 46 are initially pressurized to lOOpsi. After the initial pressurization, the pressure in cooling chamber 46 is reduced to 93psi to gradually fill the mold 26 with aluminum alloy such that there is less solidification and gas shrinkage making wrought (low silicon) aluminum alloys possible. The molten aluminum alloy is cooled by the quench media until it becomes a casted part 40 wherein the casted part 40 containing high amounts of Sr and/or Mn can be removed from the mold without being damaged from the absence of releasing agent. As shown in FIGS. 11 and 12, the cooling rate can be adjusted by the type of quench gas used, which can include one of He, N, Ar, air, etc. and the pressure of the gas. The charts in FIGS. 11 and 12 are graphical representations of gravity sand casting with 1” diameter round tensile bars. As represented, tests show a faster cooling rate when He is used as the quench media. The direct pressure gas suppresses the release of naturally occurring He in aluminum alloys, keeping it in a dissolved state thus eliminating gas porosity in the final casted part 40. Once cooled, the pressure in the fill stalk 60 and cooling chamber 46 are simultaneously reduced. During the reduction of pressure the quench media is recaptured via the port 48 or a distinct output port. The lift mechanism is then brought to the open condition and the solidified casted part 40 is ejected from the molding.

[0046] FIGS. 6 through 11 are graphical representations and charts of various embodiments of the subject disclosure. Referring first to FIG. 6, a graphical representation illustrates the introduction of quench media in units of pressure as a function of time in a chill casting system 20. FIG. 7 represents steps of the direct chill counter pressure permanent mold casting system 20 are shown as a function of time in a 90-second casting cycle when the molten material is something other than aluminum alloy containing high amounts of Sr and/or Mn and thus require the application of releasing agent. FIG. 8 illustrates a cooling rate of molten aluminum material as a function of secondary dendritic arm spacing. FIG. 9 provides a non-exhaustive list of additional molten materials that can be used with the direct chill system 20 with a comparison of material properties. FIG. 10 provides a chart comparing the cooling cycles between He and N2 gas being introduced as quench media and cooling the molten material from 950F to 400F under various pressure loads. FIG. 11 charts a comparison of cooling cycles between air, Ar, and He being introduced as quench media.

[0047] In references to the tables presented in FIGS. 12A -12C, several aluminum alloys in accordance with the subject invention are disclosed.

[0048] Referring first to Table 1, illustrated in FIG. 12A, six aluminum alloys are presented. In the embodiments presented in Table 1, the alloys comprise, in weight percent (wt.%) based on the total weight of the alloy manganese (minimum 1.2 wt.%, maximum 1.8 wt.%) in addition to: silicon (minimum 0.1 wt.%, maximum 7.5 wt.%); iron (minimum 0.15 wt.%, maximum 1.0 wt.%); copper (minimum 0.05 wt.%, maximum 5.0 wt.%); magnesium (minimum 0.1 wt.%, maximum 0.6 wt.%); zinc (minimum 0.1 wt.%, maximum 3.0 wt.%); strontium (minimum .02 wt.%, maximum 0.04 wt.%); and the remainder being aluminum.

[0049] In each of the alloy compositions of Table 1, there is a minimum of 1.2 wt.% manganese (Mn) and/or 0.04 wt.% (400 ppm) of strontium (Sr). At these levels of Mn and/or Sr or combinations of Mn, Sr and Fe, the predominantly aluminum castings affinity to the tool steel mold is reduced or eliminated and so is the required releasing agent. Because of the faster rate of cooling and solidification in the direct chill system 20, the higher amounts of Mn and or Sr with reduce or eliminate the required releasing agent. The AlMn eutectic fluidity reduces susceptibility to soldering and hot cracking. Likewise, it should be appreciated that modification of the AlSi eutectic fluidity can also reduce susceptibility to soldering due to a reduction in Fe.

[0050] Looking now to Table 2, illustrated in FIG. 12B, there are six additional aluminum alloys with additions of titanium and chromium. Titanium increases the strength of the casted part 40 while maintaining a relatively low density. Chromium increases hardness and improves surface quality of the casted part 40. A reduction of silicon avoids a brittle AlSiFeMn Phase and an increase in magnesium and/or zinc further strengthen the alloy. The addition of up to 10% in volume of Nano Alumina Decorated Aluminum as in Aluminum Alloy 1100 increases the modulus of the metal matrix composite of the casted part 40.

[0051] Turning now to Table 3, illustrated in FIG. 12C, there are additions of up to

.10 wt.% of scandium with or without up to .10 wt.% of zirconium. Additions of scandium and/or zirconium results in casted parts 40 with fine grain size, even after heat treatment, and increased strength.

[0052] FIG. 13 illustrates the reduction in time of a casting cycle using aluminum alloy in accordance with the subject invention resulting from no longer having to apply a releasing agent. As shown, the casting cycle is improved from approximately 90 seconds to approximately 80 seconds.

[0053] The afore described aluminum alloys and systems decrease the casting cycle, improves the quality of the final casting, enables the casting of materials that have traditionally proven difficult, and reduces or eliminates the required use of the releasing agent. The system and method improve infiltration of the molten aluminum alloy into the mold 26 by efficient feeding of molten aluminum alloy thus preventing the formation setbacks associated with shrinkage and metal defects such as micro porosity (natural porosity) and cavities. Elimination of the metal defects also results in better infiltration of the molten aluminum alloy between arising crystallites and plastic micro deformation during the process of crystallization. Moreover, the prolonged time of contact between the mold 26 and solidifying molten aluminum alloy before formation of the shrink gap and thereafter directly chilling via quench gas increases the depth of fine macro structure. The improved cooling process, results in smaller secondary dendritic arm spacing (DAS) which increases the mechanical properties of the final casted part 40 and, combined with above advantages, improves the ultimate tensile strength, the yield, and ductility of the casting. In the case of aluminum with low Sr content (such as aluminum alloy 6061), the increased cooling rate produces aluminum castings without the common metallurgical defects. The increased cooling rate allows casting of predominantly raw materials with additions of Mn, Sr or combinations of Mn, Sr and Fe that eliminate or reduce traditional requirements of a releasing agent. Furthermore, the improved solidification rate of the direct chill counter pressure permanent mold casting system 20 prevents wrought alloys from hot tearing as a result of absolute venting and wet out particularly through counter pressure at multiple atmospheres and/or heights. [0054] Further advantages of the subject disclosure include a shaped metal casted part

40 comprising aluminum alloy formed in the porous steel mold 26 by the direct chill casting method. The casting comprises a fine aluminum alloy solidification microstructure that is finer than the microstructure of castings having a similar metal of a similar weight or section thickness produced by a conventional steel mold casting process. The fine microstructure of the improved casting comprises one or more grains, dendrites, eutectic phases or

combinations thereof. The microstructure of the improved casting is free of porosity and comprises approximately twice as fine of microstructure than that of conventional castings. The mold 26 of the present invention can comprise of powder metal non-hipped semi sintered alloy, having a high degree of permeability. The permeability (size and concentration of pores 50) is such that it prohibits molten metal from entering the pore 50 (due to surface tension effects) while allowing a quench media to travel though the pore 50 under pressure.

As described above, the quench media (for example, liquid which may include water or gas which may include air, helium, nitrogen, argon) is forced under pressure though the porous steel mold 26 such that it contacts and directly chills the shaped metal casting.

[0055] When the aluminum alloy solidifies under the direct chill casting conditions with a higher amount of strontium (approx. 0.1 wt.% to 1 wt.%) or manganese (at least 1.2 wt.%) than the conventional aluminum alloy chemical composition, the aluminum alloy can solidify and be removed without the previous required application of releasing agent. In accordance with yet another aspect of the subject disclosure, the shaped casting includes an aggregate sand core that forms a hollow structure in the porous steel mold 26.

[0056] It should be appreciated that the foregoing description of the embodiments has been provided for purposes of illustration. In other words, the subject disclosure it is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varies in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of disclosure.

Claims

CLAIMS What is claimed is:

Claim 1. An aluminum alloy, comprising, in weight percent (wt.%) based on total weight of the alloy:

manganese in an amount up to 1.8 wt.%,

silicon in an amount of 0.1 wt.% to 7.5 wt.%,

iron in an amount of 0.12 wt.% to 1.0 wt.%,

copper in an amount of 0.05 wt.% to 5.0 wt.%,

magnesium in an amount of 0.1 wt.% to 5.0 wt.%,

zinc in an amount of 0.05 wt.% to 6.1 wt.%,

strontium in an amount up to 0.06 wt.%,

other elements each in an amount up to 0.05 wt.%,

the other elements in a total amount of up to 0.1 wt.%, and

a remaining balance of aluminum.

Claim 2. The aluminum alloy of Claim 1, including:

manganese in an amount of 1.2 wt.% to 1.8 wt.%,

silicon in an amount of 0.1 wt.% to 1.3 wt.%,

iron in an amount of 0.15 wt.% to 1.0 wt.%,

copper in an amount of 0.05 wt.% to 2.0 wt.%,

magnesium in an amount of 0.1 wt.% to 2.9 wt.%,

zinc in an amount of 0.1 wt.% to 0.25 wt.%,

strontium in an amount up to 1.0 wt.%,

other elements each in an amount up to 0.05 wt.%,

the other elements in a total amount of up to 0.1 wt.%, and a remaining balance of aluminum.

Claim 3. The aluminum alloy according to Claim 1, including: silicon in an amount of 0.1 wt.% to 1.3 wt.%,

iron in an amount of 0.15 wt.% to 0.95 wt.%,

copper in an amount of 0.05 wt.% to 2.0 wt.%,

magnesium in an amount of 0.15 wt.% to 2.9 wt.%,

zinc in an amount of 0.1 wt.% to 3.0 wt.%,

strontium in an amount of 0.02 wt.% to 0.04 wt.%,

titanium in an amount up to 0.2 wt.%,

chromium in an amount up to 0.25 wt.%,

scandium in an amount up to 0.1 wt.%,

zirconium in an amount up to 0.1 wt.%,

other elements each in an amount up to 0.05 wt.%,

Claim 4. The aluminum alloy according to claim 1, including manganese in an amount of 0.1 to 1.8 wt.%,

silicon in an amount of 5.5 wt.% to 7.5 wt.%,

iron in an amount of 0.12 wt.% to 1.0 wt.%,

copper in an amount of 0.05 wt.% to 4.0 wt.%,

magnesium in an amount of 0.1 wt.% to 0.6 wt.%,

zinc in an amount of 0.05 wt.% to 3.0 wt.%,

strontium in an amount of 0.04 wt.% to 0.06 wt.%, other elements each in an amount up to 0.05 wt.%,

the other elements in a total amount of up to 0.1 wt.%, and

a remaining balance of aluminum.

Claim 5. The aluminum alloy according to claim 1, including strontium, wherein the strontium is present in an amount of 0.04 wt.% to 0.06 wt.%.

Claim 6. The aluminum alloy according to Claim 1, including titanium in an amount of 0.1 to 0.2 wt.%.

Claim 7. The aluminum alloy according to Claim 1, including chromium, wherein the chromium is present in an amount up to 0.25 wt.%.

Claim 8. The aluminum alloy according to Claim 1, including scandium, wherein the scandium is present in an amount up to 0.1 wt.%.

Claim 9. The aluminum alloy according to Claim 1, including zirconium, wherein the zirconium is present in an amount up to 0.1 wt.%.

Claim 10. The aluminum alloy according to Claim 1, including nano alumina decorated aluminum, the nano alumina decorated aluminum being present in an amount up to 10% in volume of the aluminum alloy.

Claim 11. A casting formed of the aluminum alloy recited in claim 1.

Claim 12. The casting according to Claim 11, wherein the casting is a structural component for an automotive vehicle.

Claim 13. A method of casting a structural component for an automotive vehicle, comprising the steps of:

filling a casting chamber defined by a mold with an aluminum alloy while the aluminum alloy is molten, the aluminum alloy comprising:

manganese in an amount up to 1.8 wt.%,

silicon in an amount of 0.1 wt.% to 7.5 wt.%,

iron in an amount of 0.12 wt.% to 1.0 wt.%,

copper in an amount of 0.05 wt.% to 5.0 wt.%,

magnesium in an amount of 0.1 wt.% to 5.0 wt.%,

zinc in an amount of 0.05 wt.% to 6.1 wt.%,

strontium in an amount up to 0.06 wt.%,

other elements each in an amount up to 0.05 wt.%,

the other elements in a total amount of up to 0.1 wt.%, and

a remaining balance of aluminum.

Claim 14. The method according to claim 13, wherein the mold includes pores having a diameter of 7 to 20 microns, and including the step of filling the pores of the mold with a quench media, the quench media being liquid or gas.

Claim 15. The method according to claim 14, wherein the aluminum alloy solidifies in the casting chamber and the quench media contacts the aluminum alloy as the aluminum alloy solidifies in the casting chamber.