Casting Aluminum Alloys

545 Pages·2007·7.02 MB·English

by  Vadim S Zolotorevsky

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Casting Aluminum Alloys
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Casting Aluminum Alloys
VADIMS.ZOLOTOREVSKYandNIKOLAIA.BELOV
Moscow Institute of Steel and Alloys – State Technical University, 119049,
Moscow,4LeninskyPr.,RussianFederation
MICHAELV.GLAZOFF
AlcoaTechnicalCenter,AlcoaCenter,PA15069,USA
Amsterdam • Boston • Heidelberg • London • NewYork • Oxford
Paris • SanDiego • SanFrancisco • Singapore • Sydney • Tokyo
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C
ONTENTS
Preface ix
Notations xiii
1. AlloyingElementsandDopants:PhaseDiagrams 1
1.1 TheRoleofAlloyingElementsandDopants:BasicAlloySystems 1
1.2 PhaseDiagramsofTernarySystems 14
1.2.1 TheAl–Be–Fesystem 14
1.2.2 TheAl–Be–Sisystem 15
1.2.3 TheAl–Ce–Cusystem 16
1.2.4 TheAl–Ce–Fesystem 18
1.2.5 TheAl–Ce–Nisystem 20
1.2.6 TheAl–Ce–Sisystem 21
1.2.7 TheAl–Cr–Fesystem 22
1.2.8 TheAl–Cr–Mgsystem 23
1.2.9 TheAl–Cr–Mnsystem 24
1.2.10 TheAl–Cr–Sisystem 26
1.2.11 TheAl–Cu–Fesystem 26
1.2.12 TheAl–Cu–Mgsystem 29
1.2.13 TheAl–Cu–Mnsystem 32
1.2.14 TheAl–Cu–Nisystem 34
1.2.15 TheAl–Cu–Sisystem 36
1.2.16 TheAl–Cu–Znsystem 36
1.2.17 TheAl–Fe–Mgsystem 38
1.2.18 TheAl–Fe–Mnsystem 39
1.2.19 TheAl–Fe–Nisystem 41
1.2.20 TheAl–Fe–Sisystem 42
1.2.21 TheAl–Mg–Mnsystem 45
1.2.22 TheAl–Mg–Sisystem 45
1.2.23 TheAl–Mg–Znsystem 47
1.2.24 TheAl–Mn–Nisystem 49
1.2.25 TheAl–Mn–Sisystem 53
1.2.26 TheAl–Ni–Sisystem 54
1.3 PhaseDiagramsofFour-ComponentSystems 55
1.3.1 TheAl–Be–Fe–Siphasediagram 56
1.3.2 TheAl–Cu–Fe–Mgsystem 58
1.3.3 TheAl–Cu–Fe–Mnsystem 58
1.3.4 TheAl–Cu–Fe–Nisystem 60
1.3.5 TheAl–Cu–Fe–Sisystem 62
1.3.6 TheAl–Cu–Mg–Mnsystem 64
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vi Contents
1.3.7 TheAl–Cu–Mg–Sisystem 64
1.3.8 TheAl–Cu–Mg–Znsystem 66
1.3.9 TheAl–Fe–Mg–Mnsystem 68
1.3.10 TheAl–Fe–Mg–Sisystem 70
1.3.11 TheAl–Fe–Mn–Sisystem 74
1.3.12 TheAl–Fe–Ni–Sisystem 77
1.3.13 TheAl–Mg–Mn–Sisystem 79
1.3.14 TheAl–Mg–Ni–Sisystem 79
1.4 Five-ComponentPhaseDiagrams 81
1.4.1 TheAl–Fe–Cu–Mg–Sisystem 85
1.4.2 Five-componentSystemswithmanganese 91
2. StructureandMicrostructureofAluminumAlloysinAs-CastState 95
2.1 PhaseDiagrams,Thermodynamics,andAlloyMicrostructure 95
2.2 EquilibriumThermodynamicsandItsDevelopment 97
2.2.1 Classicalequilibriumthermodynamics 97
2.2.2 Equilibriumthermodynamicsofconcentrationally
non-uniformsystems 98
2.3 Brief Description of Solidification Microstructure Evolution in Casting
AluminumAlloysviathe“Phase-Field’’Approach 101
2.3.1 Phase-fieldapproachappliedtosolidification 102
2.3.2 Dendriticsolidificationofpuremetals 102
2.3.3 Phase-fieldmodelforsolidificationofeutecticalloys11 104
2.3.4 Solidificationmicrostructurecalculations:perspectivesand
futurework 106
2.4 QuantitativeCharacteristicsofAlloyStructureandMethodsofits
Evaluation 107
2.5 Non-EquilibriumSolidificationofBinaryAlloys 114
2.5.1 Microsegregation 115
2.5.2 Influenceofcoolingrateuponsolidificationandformationof
constituentparticlesofsecondary(excessive)phases 128
2.6 Non-EquilibriumSolidificationofMulti-ComponentAlloys 134
2.6.1 Non-equilibriumphasediagramsofmulticomponentsystems 134
2.6.2 Microsegregationinthree-componentandindustrialaluminum
alloys 145
2.7 MicrostructureofCastAluminumAlloys 154
2.8 SubstructureofCastingAluminumAlloys 162
2.8.1 Typesofdislocationstructuresinas-castaluminumalloysof
differentsystems 162
2.8.2 Theinfluenceofsolidificationconditionsupondislocation
microstructure 166
2.8.3 Themechanismsofformationofdislocationmicrostructuresin
castaluminumalloys 171
2.8.4 Decompositionofaluminumsolidsolutionintheprocessof
alloycoolingafterthecompletionofsolidification 177
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Contents vii
3. InfluenceofHeatTreatmentUponMicrostructureofCasting
AluminumAlloys 183
3.1 HomogenizingHeatTreatment 184
3.1.1 Dissolutionofnon-equilibriumconstituentparticlesinthe
courseofhomogenization 184
3.1.2 Eliminationofmicrosegregationduringhomogenization 200
3.1.3 Fragmentationandspheroidizationofconstituentparticles 213
3.1.4 Changesofgrainanddislocationmicrostructureofaluminum
solidsolutioninthecourseofhomogenization 222
3.1.5 Decompositionofaluminumsolidsolutionintheprocessof
isothermalheattreatmentbeforequenching 230
3.1.6 Developmentofporosityduringhomogenization 240
3.2 AgingAfterCastingandQuenching 240
4. DependenceofCastabilityandMechanicalPropertieson
CompositionandMicrostructureofAluminumAlloys 247
4.1 Castability 247
4.1.1 Generalcharacterizationofcastability 247
4.1.2 Concentrationdependenceofcastingproperties 258
4.2 MechanicalProperties 262
4.2.1 Geometryofelongationdiagramsforas-castandquenched
aluminumalloys,anditsconnectiontothestructural
transformationsaccompanyingdeformation 266
4.2.2 Quantitativeanalysisofrelationsbetweentensilemechanical
propertiesandstructuralcharacteristicsofcastings 280
4.2.3 Calculationsofmechanicalpropertiesofcastingsusing
thetotalityofmicrostructuralcharacteristics 295
4.2.4 Theinfluenceofcastingmicrostructureuponfracturetoughness
andfatigueproperties 302
4.2.5 Someregularitiesinchangesofmechanicalpropertieswithalloy
chemicalcomposition 311
5. IndustrialCastingAluminumAlloys 327
5.1 Al–SiAlloys 327
5.1.1 GeneralcharacterizationofAl–Sialloys 327
5.1.2 Industrial 4xx and 3xx casting alloys without copper and zinc
(“copper-less’’alloys) 336
5.1.3 IndustrialAl–Sialloyswithcopperandzinc 351
5.1.4 EnginepistonAl–Sialloys 367
5.2 AlloysontheBasisoftheAl–CuSystem 376
5.3 Al–MgandAl–Mg–ZnAlloys 386
5.3.1 GeneralcharacteristicofAl–Mgalloys 386
5.3.2 IndustrialAl–MgandAl–Mg–Znalloys 390
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viii Contents
6. NewAlloys 397
6.1 AlloyswithSmallAmountsofEutectic 397
6.2 GeneralPrinciplesofAlloyingforEutecticMaterials 405
6.3 High-StrengthAlloyAZ6N4andATs7Mg3N4(734) 418
6.4 AlloysDopedwithTransitionMetalsforImprovedThermalStability 425
6.5 AlloyswithSmallAmountsofSilicon(<4%Si) 441
Literature 449
Appendix1 CompositionsofStandardCastingAluminumAlloys 461
Appendix2 PrincipalCharacteristicsofBinaryPhaseDiagrams
ClosertoAluminumSide 487
Appendix3 GuaranteedMechanicalPropertiesofStandard
RussianAluminumAlloys 491
Appendix4 RecommendedHeatTreatmentsofStandard
RussianCastingAluminumAlloys 499
Appendix5 DataonFractureToughnessandShockToughness,
FatigueLife,CharacteristicsofThermalStability,
CorrosionResistance,andCastabilityofStandardAl–SiAlloys 507
Appendix6 DerivationofEquationsDescribingUniaxialTensileTesting
inFiniteDeformations 511
A.6.1 TheCaseofInfinitesimallySmallDeformations 513
A.6.2 TheCaseofFiniteDeformations 515
Index 523
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P
REFACE
By definition,casting alloys are materials used for the production of shape cast-
ings,thatisaluminumalloyproductswithcomplexgeometricalshape(s).Casting
aluminum alloys are quite widespread and find more and more applications in
modern industry.
According to different estimates, up to 20–30% of all aluminum products
manufactured worldwide are used for shape castings. Suffice it to say that in
additiontosuchgiantsasAlcoaInc.andAlcan,thereareliterallyhundredsofcast
housesinNorthAmerica.Aluminumcastingsarealsomanufacturedbydifferent
companies that specialize in end materials/products other than aluminum (e.g.,
General Motors,Ford,etc.)
Aluminum castings can be and indeed are produced with very substantial
amountsofrecycledaluminumscrap.Forexample,intheUSA,WesternEurope,
and Japan up to 75–80% of the overall alloy mass comes from recycled alu-
minum/scrap.This is several times higher than the corresponding numbers for
wrought aluminum alloys. Earlier it was hypothesized that the general level
of properties required of cast aluminum products was lower, and they were
used mostly for the production of non-critical (e.g., not heavily loaded) parts.
Indeed,for such parts the application of recycled aluminum with elevated levels
of impurities was quite acceptable.
However,during the last 10 or 15 years this situation has started to change.
Due to considerable improvements in casting technologies,now it is possible to
produce high-quality castings with properties that are comparable to those of
similar wrought products. Moreover,this can be done not only for high-quality
alloys, but also for those manufactured with substantial amounts of aluminum
scrap. In the latter case the advantage,of course,is in lower production costs.
Significantimprovementsinthequalityofshapecastingswereachieveddueto
improved production processes.Today it is possible to employ modern methods
of molten metal handling, which result in dramatic reduction of harmful non-
metallicimpurities.Hotisostaticpressingisusedtoreduceshrinkageporosity.All
these,andmanyother,innovationsresultinsignificantimprovementofaluminum
shape casting quality.
There are several important requirements to casting aluminum alloys: good
corrosion resistance, high level of mechanical properties (such as ultimate ten-
sile strength (UTS),yield strength (YS),and elongation (El.)) and,finally,good
castability.This last property is particularly important;it implies that solidifying
metalisnotpronetohotcracking,possessesexcellentfluidityinmoltenstate,and
minimalshrinkageporosity.ItisbecauseofexcellentcastabilitythatAl–Sicasting
alloys (containing more than 4%Si) have retained their leading role among all
othercastingalloycompositionsduringthelast60years,eventhoughthegeneral
ix