This document discusses the basics of aluminum alloys used in metalcasting. It explains that cast alloys have different compositions than wrought alloys and are designed specifically for casting. Common alloying elements like silicon, magnesium, copper, and zinc are added to aluminum to improve properties like fluidity, strength, and corrosion resistance. Unwanted elements like iron can make alloys more brittle. Gases like hydrogen and oxygen must also be controlled to prevent defects. Grain refiners and modifiers can further improve mechanical properties of cast aluminum alloys.

1. 1Aluminum Foundry Alloy Basicsfor BackyardMetalcasting.com Foundry JoeRev 0, May 2010

2. 2ContentBasics of Aluminum AlloysCast vs. WroughtPrimary vs. SecondaryUnderstand Alloy Element EffectsDeliberate AdditionsSi, Mg, Cu, Zn, BeUnwanted AdditionsFe, OthersEffects of Gases (H2, O2)Grain Refiners (TiBor)Modifiers (Sr)

3. 3Aluminum Alloy Applications

4. 4Basics of Aluminum AlloysWrought alloys Wrought means “worked”Rolled, Extruded, Forged6061, 7075 Aircraft Aluminum3104 Beer cansCasting alloys are different than wroughtHave been specifically designed to be cast and not worked

5. 5Aluminum Foundry Casting AlloysIn North America the Aluminum Association numbering system is most commonWrought alloys series have 4 numbers1000 to 9000 series6061, 7075 are familiar examplesFoundry alloy series have 3 numbers100 series to 800 series319, 356, 380 are the most common foundry alloysThere are more than 60 foundry alloysBut just a few make up 80% of tonnage cast

6. 6Wrought vs. Cast Aluminum

7. 7Primary vs. Secondary AlloysPrimary AlloyProduced from ore at a smelterVirgin ingot – first time usedMore expensiveSecondary AlloyProduced from scrap by a recyclerLower costDoes NOT mean low quality!

8. 8Some Foundry Alloy ExamplesFoundry Alloys are mostly aluminum with 2 or 3 deliberate additions of alloying elements to improve propertiesThey also have some unwanted elements which usually reduce properties

9. 9What do all these Alloying Elements Do?Deliberate Alloy AdditionsSi, Mg, Cu, ZnUnwanted Alloy AdditionsFe, Many OthersOther AdditivesGrain Refiners (TiBor)Modifiers (Sr)Effects of Gases (H2, O2)

10. 10Deliberate Alloy AdditionsThese alloy elements are added by designAdded on purpose, to create some kind of a benefitThe “Big One” is SiliconDevelops a property called “fluidity”Next biggest is MagnesiumAllows the alloy to respond to heat treat for improved strength

11. What is Meant by Fluidity? Fluidity is how far the alloy will flow before freezingIf the alloy freezes before it fills the mold you get a short pour misrun, or cold shutYou could just make the metal hotter (superheat) so it will run more before freezingBut that takes energy and costs moneyThis pattern is poured to measure fluidity 11

12. How to Improve Fluidity? Instead of making the metal hotter we can alloy the Aluminum to lower the melting point, sothe alloy will run farther for a given temperatureAn eutectic alloy has this propertyThis is best seen on a phase diagramA Degree in Metallurgy follows on the next 3 slides12

13. 13Solder Phase DiagramSolder is an Eutectic Alloy mean lowest melting pointPure Tin melts at 446°F 230°CPure Lead melts at 626°F 330°CBUT!A 60/40 mix melts at 338°F 170°COne hundred degrees F cooler!Less energy required to melt!Solid

14. 14Aluminum Silicon Phase DiagramAluminum Silicon is also an Eutectic AlloyPure Aluminum melts at 1220°F 660°CPure Silicon melts at 2552°F 1400°CBUT!An 11.7% mix melts at 1070°F 577°COne hundred fifty degrees F cooler!Less energy required to melt!LIQUIDSLUSHSOLIDPouring temp is temp above melt point required to fill thinnest section before freezingSo by using a eutectic alloy, can reduce the pouring temp

15. 15Silicon Content of Foundry Alloys319 alloyengine blocks heads, intakesLIQUID390 alloyVega engine block380 alloytransmission casesSLUSHSLUSH413 eutectic alloy“perfect” foundry alloy - lowest shrinkSOLID

16. Review of Element Effects16

17. 17Base Element – Aluminum (Al)100 Series Alloys are mostly Aluminum13th element on Periodic TableAluminum has limited use in pure form Electrical wire, electric motor rotorsVery tricky to castUsually mixed with other elementsMix of elements is “an Alloy”

18. 18Effects Of Alloy Elements – Silicon (Si)300 & 400 Series Alloys have Silicon addedSiO2 is quartz <sand – used to make glass> Added to improve castabilityincreases fluidity, reduces shrinkageSilicon and Magnesium togethermakes alloy heat treatable for strength356 and 413 alloys are high Silicon alloysNice to cast

19. 19Effects Of Alloy Elements – Copper (Cu)200 Series Alloys have Copper addedCopper increases strengthReduces corrosion resistanceIncreases shrinkage makes alloy more difficult to cast

20. 20Effects Of Alloy Elements – Magnesium (Mg)300 & 500 Series Alloys have Magnesium addedSilicon and Magnesium togethermakes alloy heat treatable for strengthIncreases shrinkage makes alloy more difficult to cast

21. 21Effects Of Alloy Elements – Zinc (Zn)700 Series Alloys have Zinc addedZinc and Aluminum has bright surface finishgood corrosion resistance good strengthIncreases shrinkage makes alloy more difficult to cast

22. 22Unwanted Alloy Additions - TrampsThese alloy elements are not wantedCan’t be helpedFrom smelting processFrom scrap recyclingFrom contact with iron crucibles, toolsThey cause some kind of harmLower strengthWorse castabilityTramp Elements

23. 23Effects Of Alloy Elements – Iron (Fe)Iron Oxide is rust Iron makes an Alloy more brittleGenerally regarded as badTry to keep as low as possibleAluminum is an aggressive solvent for ironSteel crucibles & tools dissolve in AluminumUse a coating

24. 24Alloy MicrostructureAluminium is soft and ductileSilicon is hard and brittleBoth = strongerThink Fiberglas Glass & ResinSiBrittleDarkColorAlSoftLight Color

25. 25Iron in MicrostructureSiBrittleAlSoft(Fe,Mn)3Si2Al15Chinese Script (-Fe)FeSiAl5Needles (-Fe)A crack along the brittle Iron phase

26. 26Other Minor Tramp ElementsChromium, Nickel, Tin

27. Lithium, Calcium, Phosphorous

28. Others

29. Each and Total

30. Just control them under the spec limit

31. How?

32. Add more Aluminum to dilute them down27Effects of Gases on AlloysGases also have a major <bad> effect on Aluminum alloysHydrogenOxygen