WO2023023704A1 - Improved aluminium based casting alloy - Google Patents
Improved aluminium based casting alloy Download PDFInfo
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- WO2023023704A1 WO2023023704A1 PCT/AU2022/050921 AU2022050921W WO2023023704A1 WO 2023023704 A1 WO2023023704 A1 WO 2023023704A1 AU 2022050921 W AU2022050921 W AU 2022050921W WO 2023023704 A1 WO2023023704 A1 WO 2023023704A1
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- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 153
- 239000000956 alloy Substances 0.000 title claims abstract description 153
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 36
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 239000004411 aluminium Substances 0.000 title claims abstract description 33
- 238000005266 casting Methods 0.000 title claims description 67
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 15
- 239000010703 silicon Substances 0.000 claims abstract description 15
- 229910052712 strontium Inorganic materials 0.000 claims abstract description 14
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052742 iron Inorganic materials 0.000 claims abstract description 13
- 239000011572 manganese Substances 0.000 claims abstract description 13
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 12
- 239000011701 zinc Substances 0.000 claims abstract description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000011777 magnesium Substances 0.000 claims abstract description 10
- 239000010949 copper Substances 0.000 claims abstract description 9
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 239000010936 titanium Substances 0.000 claims abstract description 9
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 8
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 8
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000011651 chromium Substances 0.000 claims abstract description 7
- 229910052802 copper Inorganic materials 0.000 claims abstract description 7
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 7
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052790 beryllium Inorganic materials 0.000 claims abstract description 6
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 claims abstract description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 238000005495 investment casting Methods 0.000 claims description 31
- 239000000203 mixture Substances 0.000 claims description 23
- 238000000034 method Methods 0.000 claims description 20
- 210000001787 dendrite Anatomy 0.000 claims description 18
- 238000007528 sand casting Methods 0.000 claims description 18
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 15
- 229910000838 Al alloy Inorganic materials 0.000 claims description 14
- 239000004576 sand Substances 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 229910052723 transition metal Inorganic materials 0.000 claims description 3
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 2
- 238000001816 cooling Methods 0.000 description 13
- 238000004512 die casting Methods 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 230000008569 process Effects 0.000 description 9
- 239000000463 material Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 229910018594 Si-Cu Inorganic materials 0.000 description 6
- 229910008465 Si—Cu Inorganic materials 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 238000005476 soldering Methods 0.000 description 6
- 238000007711 solidification Methods 0.000 description 6
- 230000008023 solidification Effects 0.000 description 6
- 238000003483 aging Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 4
- -1 aluminium-silicon- copper Chemical compound 0.000 description 4
- 229910052796 boron Inorganic materials 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- 229910052709 silver Inorganic materials 0.000 description 4
- 239000004332 silver Substances 0.000 description 4
- 238000002076 thermal analysis method Methods 0.000 description 4
- 229910018566 Al—Si—Mg Inorganic materials 0.000 description 3
- 238000005275 alloying Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 230000001627 detrimental effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910017818 Cu—Mg Inorganic materials 0.000 description 2
- 238000007792 addition Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000013467 fragmentation Methods 0.000 description 2
- 238000006062 fragmentation reaction Methods 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 238000001016 Ostwald ripening Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000009866 aluminium metallurgy Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 229910001095 light aluminium alloy Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 238000010120 permanent mold casting Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000001393 triammonium citrate Substances 0.000 description 1
- 229910052845 zircon Inorganic materials 0.000 description 1
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/026—Alloys based on aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
Definitions
- the present invention relates to an aluminium based alloy for the manufacture of cast parts.
- the invention particularly relates to aluminium-silicon- copper based casting alloys suitable for sand or investment casting and it will be convenient to hereinafter disclose the invention in relation to that exemplary application.
- the invention is not limited to that application and could be used in a number of low pressure casting processes.
- Typical age hardenable aluminium castings are based around the Al-Si-X alloying system, with a range of alloying elements present.
- Other, less common alloy systems include those based around the Al-Cu-X system, which are also age-hardenable alloys.
- the advantages of the Al-Si-X alloys include low cost and very good castability especially when using methods such as sand casting, low pressure casting, and investment casting.
- alloys in the Al-Cu-X family of castings have relatively poor castability and are prone to hot tearing, but they may develop high levels of strength properties, especially when silver is added to their composition. These silver containing alloys have a significant cost penalty associated with their use, since even 0.5% silver can double the base price of a primary alloy.
- AMS-A- 21 180C (“Aluminum-Alloy Castings, High Strength”) is a widely used example that is also reflective of the contents of the MMPDS (Metallic Materials Properties Development and Standardization).
- MMPDS Metallic Materials Properties Development and Standardization
- the high strength aluminium alloy castings covered by AMS-A-21180C (2017) are intended for airframe, missile, and other applications where high strength, ductility, soundness and uniform composition within each casting are required.
- AMS-A-21180C covers the basic requirements for cast aerospace alloys A201 -T7, 354-T6, C355-T6, A356-T6, A357-T6, D357- T6, and 359-T6.
- the composition of these is shown in Table 1.
- D, E and F357 for example, which are slightly modified version of the base A357 alloy.
- a more complete overview of common alloys and their variants may be found in the Aluminum Association Pink Sheets (i.e. Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot).
- high pressure diecasting alloys are that they must contain high levels of iron or combined iron + manganese, at around 1 % total content, to avoid die soldering.
- Donohue and Lumley (R. J. Donahue & R. N. Lumley, Chapter 6, New Hypoeutectic I Hypereutectic die casting alloys and new permanent mold casting alloys that rely on strontium for their die soldering resistance, in Fundamentals of Aluminium Metallurgy, Recent Advances, R. N.
- the dendrite arm spacing of a high pressure diecasting may be in the range of 1 to 5
- the dendrite arm spacing of an investment casting may be reduced to around 20 to 40
- B380 composition is the same as A 380 but with a maximum 1 .0%Zn;
- composition is the same as C380 but with a maximum 1 .0%Zn;
- E380 composition is the same as C380 but the lower limit of Mg is absent.
- Table 4 summarizes similar alloys to Table 3 which are listed in the Aluminum Association pink sheets as registered alloys, but which are used as sand castings. Similar to Table 3, these all have high allowances of transition metal elements such as Fe, Mn, and Ni. Furthermore, ASTM B26 -18e1 provides tensile mechanical properties for Alloy 319.0 in a heat treated T6 condition and has minimums of 140 MPa yield strength, 215 MPa tensile strength, and >1.5% elongation, for purposes of comparison.
- the present invention provides an aluminium-silicon-copper based casting alloy which can be cast to produce a casting having high strength combined with good levels of tensile ductility.
- a first aspect of the present invention provides an aluminium based alloy consisting essentially of a weight percentage composition of: silicon 4.0 to 8.5% magnesium 0.07 to 0.3% titanium 0.06 to 0.2% manganese ⁇ 0.05% iron ⁇ 0.15% chromium ⁇ 0.01 % nickel ⁇ 0.01 % copper 2.5 to 4% zinc 0 to 0.5% strontium >0.001 to 0.03% beryllium less than 0.0005% tin less than 0.01 % other elements (each) less than 0.05% each other elements total less than 0.15% in total, and a balance of aluminium and other unavoidable impurities.
- Silicon is required in the alloy to depress the melting temperature, aid fluidity and increase strength. Compositions range within the limits of 4.0 to 8.5 wt%, but all maintain good fluidity to aid casting.
- the Si level is preferably from 4.0 to 7.5 wt%, more preferably 4.5 to 7.5 wt%. This corresponds to optimal casting conditions for the majority of instances and higher levels are not necessarily beneficial. In some embodiments, the Si level is 4.0 to 5.5 wt%, preferably about 5 wt%.
- the alloy of the invention is surprisingly less sensitive to cooling rate and can generate good strength and ductility levels at dendrite arm spacing such as between 35 and 40
- Magnesium content of 0.07 to 0.3 wt% is a key part of the alloy of the invention. Greater additions of magnesium, such as >0.3 to 0.35 wt%, are not beneficial in the alloy of the current invention and may cause reductions in ductility or greater sensitivity to dendrite arm spacing. In embodiments, optimal concentration typically is found to be > 0.1 wt% and ⁇ 0.25 wt%, and more preferably around 0.15 to 0.25 wt%, preferably 0.15 to 0.2 wt%.
- Titanium may be present in small but measurable quantities, of 0.06 up to 0.2 wt%, and its presence is critical for the efficacy of the present invention. Too much titanium in the alloys leads to negative effects that may reduce tensile elongation. Too little titanium and boron may cause the alloy to “run out” of grain refiner during the solidification process, impacting grain structure.
- One of the other elements that can be present in the alloy is boron.
- Boron is present in the alloy in amounts less than 0.05 wt%.
- boron is present together with the Ti, normally in a ratio of 5:1 or 3:1 for example, depending on the composition of the master alloy added to the alloy.
- iron and manganese should ideally be kept as low as possible, and preferably, the combined iron and manganese content (sum of Fe +Mn) is preferably less than 0.1 wt%.
- Copper is present to aid fluidity and to provide strengthening to the alloy by heat treatment, especially when in combination with magnesium and silicon.
- Cu levels around 3 to 3.75 wt%, preferably 3 to 3.5 wt%, are optimal in the present invention, but levels as low as 2.5 wt% and as high as 4 wt% may also be considered in some applications. More generally however, the advantages of the alloy type are reduced compared to incumbent Al-Si-Mg alloys if the Cu content is too low or too high.
- Zinc may be present at levels up to 0.5%, but its preferable to maintain its level below 0.3 wt%. Higher levels should be avoided. In embodiments, zinc is present from 0.1 to 0.3 wt%. Zinc in these levels is not detrimental to the efficacy of the invention. Higher levels create a weight or density penalty so should be avoided wherever possible.
- the copper + zinc content must be less than 4 wt% and preferably less than 3.6 wt%.
- Strontium is known as a modifier to silicon in cast aluminium alloys, and has been found in this work to have a more significant effect in the Al-Si-Cu alloys of the invention compared to Al-Si-Mg alloys such as A356 and A357. Whilst not wanting to be limited to any one theory, the presence of strontium may be crucial to promote modification of the silicon present. Here it is also important to note, that F380 alloy as shown in Table 3, has had Sr added to prevent die soldering rather than to change the morphology of the silicon phase. The presence of strontium in the range of >0.001 to 0.03 wt% and preferably 0.01 to 0.025 wt% is necessary to achieve the best combinations of mechanical properties in the alloy.
- strontium is present at from 0.01 to 0.015 wt%. Too much strontium increases porosity and may be detrimental to the outcome of the invention. However, there are instances where Sr is detrimental to the surface finish of investment castings through a metal-mould reaction initiated by strontium, and in these cases the strontium content must be maintained between 0.001 and 0.008 wt%, preferably 0.001 to 0.005 wt%. In some embodiments, the strontium content is present at from 0.001 to 0.007 wt%.
- Beryllium is known to provide various advantages to aluminium alloys, particularly in changing the morphology of iron bearing phases. It is however highly toxic and should not be permitted or included in the alloy. Similarly, tin should be omitted entirely within the alloy of the invention or restricted to only trace levels as specified. Due to toxicity and environmental concerns regarding Cr, it is preferable to limit Cr content to a minimum, preferably ⁇ 0.002%.
- the content of nickel in the aluminium based alloy is controlled to be less than 0.01 wt%.
- the composition is free of beryllium, rare earth elements, and free of chromium and other transition metal elements not including (i.e. with the exception of) Ti, Mn, Fe, Ni, Cu, Sr and Zn.
- the alloy of the present invention is most highly suited to the processes of investment casting and sand casting, but may also find utility with other casting techniques such as gravity casting or low pressure casting.
- the alloy of the present invention comprises a casting alloy for casting processes having a casting pressure of less than 10 bar.
- the casting pressure will be no more than 5 bar, and typically no more than 2 bar.
- the casting pressure will be around atmospheric pressure up to around 2 bar.
- sand casting or investment casting are conducted around atmospheric pressure.
- the alloy can therefore comprise a sand casting alloy or an investment casting alloy.
- the alloy can be cast into any suitable shape or form.
- the aluminium based alloy comprising and/or is cast as an ingot of alloy.
- Castings of the alloy are also suitable for and may be produced by high integrity premium casting processes to achieve minimum levels of porosity and finer microstructures.
- the castings may be used together with chills or artificial cooling for critical locations to achieve fine microstructures.
- the alloys of the invention are not suitable for high pressure diecasting.
- the alloy is unsuitable for pressure diecasting because it does not meet the requirement of (10xSr)+Fe+Mn >1 , mentioned earlier.
- a second aspect of the present invention provides a method of fabricating an aluminium-based alloy product, the method comprising: providing an aluminium alloy melt from the aluminium-based alloy according to the first aspect of the present invention; and casting said aluminium alloy melt into a mould using a using a casting process having a casting pressure of less than 10 bar.
- the method of this second aspect is highly suited to the processes of investment casting and sand casting, but may also find utility with other casting techniques such as gravity casting.
- the cast alloy can be subjected to any number of secondary treatment processes including but not limited to heat treatment including tempering, annealing or the like, age hardening, solution heat treatment or the like.
- heat treatment procedures may be utilised, such as T4, T5, T6, T7, T8 or T9 tempers, depending on the desired material properties and result.
- a third aspect of the present invention provides a cast product produced using the aluminium based alloy of the first aspect of the present invention. That product is preferably produced using a casting process having a casting pressure of less than 10 bar and often less than one bar such as investment casting and sand casting. In most embodiments, the casting pressure will be no more than 5 bar, and typically no more than 2 bar. In many embodiments, the casting pressure will be around atmospheric pressure up to around 2 bar.
- the present invention can be used to produce various cast products, such as a sand cast product, an investment cast product, or an aluminium alloy based casting.
- the alloy is used to form a product or component cast comprising a structural aerospace casting.
- the alloy can be cast into any suitable shape or form.
- the cast product comprises an ingot of alloy.
- the cast product can have various morphologies.
- the microstructure of the alloy includes dendrites (is dendritic), and has a dendrite arm spacing of less than 50
- Figure 1 shows a thermal analysis scan of Al-Si-Cu alloys in accordance with the present invention.
- Figure 2 shows the microstructure generated from an investment casting made from Alloy 1 .
- Figure 3 shows the microstructure generated from an investment casting made from Alloy 2.
- Figure 4 shows the microstructure generated from an investment casting made from Alloy 3.
- Figure 5 shows the microstructure generated from an investment casting made from Alloy 4.
- Figure 6 shows the microstructure generated from an investment casting made from Alloy 5.
- Figure 7 shows a hardness time curve comparing age hardening after solution treatment at 490 °C and water quenching, comparing the hardening response of Alloy 4 and Alloy 5 when age hardened at 150 °C.
- the present invention provides an aluminium-silicon-copper based casting alloy which can be cast to produce a casting having high strength combined with good levels of tensile ductility.
- Castings of the alloy may be produced by sand or investment castings, and other lower pressure casting processes and techniques.
- the alloys of the invention are not suitable for high pressure diecasting because it does not meet the requirement to avoid die soldering of (10xSr)+Fe+Mn >1 , discussed above.
- the castings may be produced by high integrity premium casting processes to achieve minimum levels of porosity and finer microstructures.
- the castings may be used together with chills or artificial cooling for critical locations to achieve fine microstructures.
- a wide variety of heat treatment procedures may be utilised, such as T4, T5, T6, T7, T8 or T9 tempers for example, depending on the desired result.
- Figure 1 shows a thermal analysis scans showing cooling curves of Al-Si- Cu alloys in accordance with the present invention. These were conducted using a standard thermal analysis method wherein a molded sand cast cup is used and the change in temperature is recorded as the metal cools.
- the sand molded cup for tracking the cooling curve is known as a QuiK-Cup-(without Te) commercially available from Heraeus Electronite, which is connected directly to a Picolog TC- 08 datalogger.
- a small sample of molten aluminium is taken from the prepared melt and poured into the sand cup, which contains a thermocouple and enables an accurate logging of the change in temperature of the metal under standard conditions.
- the resulting cooling curves are shown in Figure 1 .
- the top curve corresponds to Alloy 1 from Table 5 whereas the bottom two curves correspond to Alloy 2 and 3 from Table 5, thereby highlighting differences in low iron alloys with or without Sr.
- the curves are characterized by three main features. (1 ) The onset of solidification occurs at around 600 °C; (2) there is a thermal arrest at around 555 °C, and (3) solidification finishes at close to 500 °C. The thermal arrest common in Al-Si-Cu alloys containing iron, and forming 0- AhFeSi at close to 575 °C is absent.
- the cooling curves are characterised by a relatively long duration where liquid phase is present in the alloy which is advantageous for interdendritic feeding. Where Sr is added, the onset of eutectic solidification occurs at a lower temperature and finishes at a higher temperature.
- the cast to shape test bars comply with the dimensional requirements of ASTM B557, for a 0.25” gage diameter.
- the molten alloys were prepared from various primary and secondary feedstocks, such as ingot, returns, master alloys and alloying elements added to the metal. The composition was verified with a Spectromaxx Spectrometer. The metal temperature prior to casting was typically 710 °C.
- Figure 2 shows the as cast microstructure of Alloy 1 , produced as an investment casting. After casting, the test pieces were removed from the cast tree and heat treated to a T6 temper. For this process, the alloy was solution treated for 22 h at 490 °C prior to water quenching and ageing 24 h at 150 °C. Figure 2 shows that the silicon structure is reasonably coarse despite the very long times of solution treatment. The dendrite arm spacing was measured to be 37
- Figure 3 shows the microstructure of Alloy 2 and Figure 4 shows the microstructure of Alloy 3. For the purposes of comparison, these are shown together as they are a close representation of a repeated test. Alloy 2 displays a DAS of 16.3 jim and Alloy 3 displays a DAS of 14.4 jim and the microstructures are effectively identical. In difference to Alloy 1 , the silicon phase is well distributed and fragmented in both alloys.
- Figure 5 shows the microstructure of Alloy 4 and Figure 6 shows the microstructure of Alloy 5, both treated to a T6 temper in the same means as discussed above for Alloy 1 .
- the principle difference was in the Mg content of the two alloys, but they also were prepared using less than 5 wt% silicon. Each displayed a dendrite arm spacing of 23.9 jim or 26.2 jim respectively. Because of their lower silicon content, these alloys have a moderately different solidification behaviour to the alloys 1 to 3.
- Figure 7 shows a hardness-time curve describing the age hardening behaviour of alloys 4 and 5.
- the hardness-time curve was obtained using a Vickers hardness tester with a 10 kg load. Most importantly, the combination of high copper content and higher magnesium content work together in alloy 5 to produce improved strengthening.
- Table 7 shows the tensile properties of the five alloys as investment castings in the as-cast condition for purposes of comparison. These tensile properties were obtained using the specimens cast to shape and tested in accordance with ASTM B557.
- Table 8 shows the average tensile properties for investment castings manufactured from each of the five alloys tested, heat treated to a T6 temper. The material was solution treated at 490 °C for 22 h, water quenched, then aged 24 h at 150 °C. These tensile properties were obtained using the specimens cast to shape and tested in accordance with ASTM B557. [062] Table 8 also shows for Alloy 4, results for the investment cast alloy displaying a dendrite arm spacing of 23.9 jim (T6#1 ) or 38.4 jim (T6#2). The larger dendrite arm spacing shows a moderate reduction in tensile mechanical properties, however the level of strength achieved is still excellent. These tensile properties were obtained using the specimens cast to shape and tested in accordance with ASTM B557.
- Table 9 shows the average tensile properties for Alloys 1 to 5, in the T4 temper. The material was solution treated at 490 °C for 22 h, water quenched, then aged a minimum of 14 days at 22 °C. These tensile properties were obtained using the specimens cast to shape and tested in accordance with ASTM B557.
- Table 10 shows the composition of a test aerospace casting of a part where the test bars were integrally cast with the part.
- Table 11 shows the mechanical properties of the test casting of Table 10 and the results of tensile testing a sand casting produced from the same alloy. These tensile properties were obtained using the specimens cast to shape and tested in accordance with ASTM B557 for the investment casting or AS1391 for the sand casting and were generated by third party testing at (Bureau Veritas Asset Integrity and Reliability Services Australia Pty. Ltd., Regency Park, South Australia).
- the investment casting was produced with a shell temperature of 700 °C and a metal pour temperature of 720 °C.
- the results of Table 11 were generated from alloy heat treated to a T6 temper, with a solution treatment of 24 h at 490 °C, water quenched, and aged 24 h at 150 °C.
- Each material meets the design requirements that would normally be considered suitable for alloy 201 -T7, Class
- Table 11 Tensile properties from the Al-Si-Cu-Mg alloy shown in Table 10 for an investment casting produced with a shell temperature of 700 °C and a metal pour temperature of 720 °C.
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US20110100515A1 (en) * | 2008-04-30 | 2011-05-05 | Roger Neil Lumley | Aluminium based casting alloy |
US20110126947A1 (en) * | 2008-07-30 | 2011-06-02 | Rio Tinto Alcan International Limited | Casting made from aluminium alloy, having high hot creep and fatigue resistance |
GB2553366A (en) * | 2016-09-06 | 2018-03-07 | Jaguar Land Rover Ltd | A casting alloy |
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US20110100515A1 (en) * | 2008-04-30 | 2011-05-05 | Roger Neil Lumley | Aluminium based casting alloy |
US20110126947A1 (en) * | 2008-07-30 | 2011-06-02 | Rio Tinto Alcan International Limited | Casting made from aluminium alloy, having high hot creep and fatigue resistance |
GB2553366A (en) * | 2016-09-06 | 2018-03-07 | Jaguar Land Rover Ltd | A casting alloy |
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Title |
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ZHU X ET AL.: "Effect of Frequency, Environment, and Temperature on Fatigue Behavior of E319 Cast-Aluminum Alloy: Small-Crack Propagation", METALLURGICAL AND MATERIALS TRANSACTIONS A, vol. 39, November 2008 (2008-11-01), pages 2666 - 2680, XP019696402 * |
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