【精品】metallurgical fundamentals 冶金学(可编辑.ppt
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1、Metallurgical Fundamentals 冶金学Metallurgical Fundamentalsn nCrystal GeometryCrystal Geometryn nMetallic PropertiesMetallic Propertiesn nPlastic DeformationPlastic Deformationn nSingle Crystals vs.PolycrystalsSingle Crystals vs.Polycrystalsn nPhase DiagramsPhase Diagramsn nStrengthening MechanismsStre
2、ngthening Mechanismsn nSoftening ProcessesSoftening Processesn nTopics on SolidificationTopics on Solidificationn nDiffusionDiffusionCrystal GeometryCrystal Geometryn nCrystalline solids have periodic,ordered 3-D Crystalline solids have periodic,ordered 3-D arraysarraysn nThese arrays can be describ
3、ed in terms of a unit These arrays can be described in terms of a unit cellcelln nSeven basic crystal systems interatomic Seven basic crystal systems interatomic distances and anglesdistances and anglesuuCubic,tetragonal,orthorhombic,rhombohedral,hexagonal,Cubic,tetragonal,orthorhombic,rhombohedral,
4、hexagonal,monoclinic,triclinicmonoclinic,triclinicn nFurther symmetries result in 14 different space,or Further symmetries result in 14 different space,or Bravais,latticesBravais,latticesBravais LatticesBody-Centered Cubicn nLower atomic packing Lower atomic packing factorfactorn nProperties are fai
5、rly Properties are fairly isotropicisotropicn nExamplesExamplesuuAlpha-iron(RT 911Alpha-iron(RT 911 C)C)uuDelta-iron(1392Delta-iron(1392 C MT)C MT)uuVanadiumVanadiumuuMolybdenumMolybdenumuuChromiumChromiumuuTungstenTungstenHexagonal Close Packedn nPacking factor varies Packing factor varies with pla
6、ne of interestwith plane of interestn nAnisotropicAnisotropicn nExamplesExamplesuuTitaniumTitaniumuuMagnesiumMagnesiumuuCobaltCobaltuuZincZincuuCadmiumCadmiumuuZirconiumZirconiumMetallic PropertiesStructure-Propertiesn nSimilar crystal structure=similar propertiesuuBCC t tshow DBTTshow DBTTt tdeform
7、 more easily at high Tdeform more easily at high TuuFCCt tlower diffusion rate good creep resistancelower diffusion rate good creep resistanceuuHCPt tproperties are anisotropicproperties are anisotropicMelting Point-Strengthn nPure Annealed MetalsuuMelting points grouped by crystal structureMelting
8、points grouped by crystal structureuuRoom temperature strength correlates to Room temperature strength correlates to melting pointmelting pointuuAt same fraction of MP,all metals have similar At same fraction of MP,all metals have similar strengthstrengthMelting Point-StrengthMetalMetalRT RT Crystal
9、 Crystal StructureStructureMelting Melting Point Point(C)(C)UTS UTS(MPa)(MPa)(RT)(RT)RT/RT/MPMPCadmiumCadmiumHCPHCP32132170700.0620.062MagnesiumMagnesiumHCPHCP65065090900.0310.031AluminumAluminumFCCFCC66066045450.0300.030CopperCopperFCCFCC108510852092090.0180.018IronIronBCCBCC153815382072070.0130.01
10、3TitaniumTitaniumHCPHCP166816682352350.0120.012ChromiumChromiumBCCBCC187518752822820.0110.011TungstenTungstenBCCBCC341034109459450.0060.006Melting Point-Strengthn nPure Annealed MetalsuuMelting points grouped by crystal structureMelting points grouped by crystal structureuuRoom temperature strength
11、correlates to Room temperature strength correlates to melting pointmelting pointuuAt same fraction of MP,all metals have similar At same fraction of MP,all metals have similar strengthstrengthn nWorked and Alloyed MetalsuuThese rules are thrown out the window,as we These rules are thrown out the win
12、dow,as we shall see.shall see.Densityn nDensityuuImportant consideration for designImportant consideration for designuuValues for metals range 1.74 g/cc for Values for metals range 1.74 g/cc for magnesium to 19.30 g/cc for goldmagnesium to 19.30 g/cc for golduuValues for non-metals(polymers&elastome
13、rs)Values for non-metals(polymers&elastomers)generally 1.0 to 3.0 g/ccgenerally 1.0 to 3.0 g/ccn nSpecific Strength or StiffnessuuBetter design criteriaBetter design criteriaDensity Strength:WeightElementElementRT RT DensityDensityMagnesiumMagnesium1.741.74AluminumAluminum2.702.70TitaniumTitanium4.5
14、14.51IronIron7.877.87ChromiumChromium7.197.19CadmiumCadmium8.648.64CopperCopper8.928.92TungstenTungsten19.2519.25ElementElementSpecific Specific StrengthStrengthTitaniumTitanium5252MagnesiumMagnesium5252TungstenTungsten4949ChromiumChromium3939IronIron2626CopperCopper2323AluminumAluminum1616CadmiumCa
15、dmium8 8Density Strength:WeightAlloyAlloyRT RT DensityDensityAZ91DAZ91D1.811.81319 T6319 T62.792.79356 T6356 T62.692.69380-F380-F2.712.71TiAl4TiAl44.494.491040 Q&T1040 Q&T7.637.63D5506D55067.157.15104010407.847.84AlloyAlloySpecific Specific StrengthStrengthTiAl4TiAl4223223AZ91DAZ91D126126380-F380-F1
16、161161040 Q&T1040 Q&T102102104010407979356 T6356 T67878319 T6319 T67777D5506D55067777Single Crystals vs.PolycrystalsSingle Crystals vs.Polycrystalsn nMost discussion so far has concerned single crystalsn nThe tendencies related thus far are amplified or negated in polycrystalline materialsSingle Cry
17、stal Materialsn nAtoms in Bravais lattice arranged in same direction(crystallographic orientation)n nShow isotropy/anisotropy of Bravais latticen nDifficult to produce in large componentsn nImportant in creep-resistant applications(turbine blades)Polycrystalline Materialsn nMade up of groups of sing
18、le crystals(grains)uu10 100 microns10 100 micronsn nEach crystal has its own crystallographic orientationn nRegions between crystals(grain boundaries)have higher energy due to local distortion of atomic orderPolycrystals(cont.)n nRandom crystallographic orientation results in isotropyn nCommon engin
19、eering metals are polycrystallineuuEase of production,isotropic propertiesEase of production,isotropic propertiesn nProduction methods effect grain size and orientationn nGrain size and orientation can effect isotropyPhase DiagramsPhase Diagramsn nPhase diagrams describe the phases present in any mi
20、xture of two elements at standard pressure over the range of temperatures exceeding the melting pointuuAssume everything happens in equilibriumAssume everything happens in equilibriumuuNOTHING happens in equilibrium,but well NOTHING happens in equilibrium,but well deal with that later.deal with that
21、 later.Complete Solid Miscibilityn nElements are Elements are completely soluble at completely soluble at all concentrationsall concentrationsn nExample:Cu-Ni Example:Cu-Ni systemsystemuuTerminology Terminology liquidus,solidusliquidus,solidusuuLever RuleLever RulePartial Solid Miscibilityn nOne ele
22、ment is soluble in the other only to a certain extentn nBasis for precipitation hardeningn nAt intermediate concentrations in the liquid state,a three-phase reaction occursuuEutectic(L Eutectic(L +)Pb-Sn system)Pb-Sn systemuuPeritectic(Peritectic(+L +L )Fe-C system)Fe-C systemPartial Solid Miscibili
23、tyPartial Solid MiscibilityPartial Solid Miscibilityn nThree-phase reactions also occur in solid staten nAnalogous to liquid state reactionsuuEutectiod(Eutectiod(+)Fe-C system)Fe-C systemuuPeritectiod(Peritectiod(+)Solid State ReactionsStrengthening MechanismsDeformationn nWhen subject to stress,int
24、eratomic distance increases elastic deformationn nBeyond the elastic limit(yield point),no further increase in interatomic distanceuuAdditional deformation is due to atomic movement plastic deformationt tSlipSlipt tTwinningTwinningSlipn nPrimary mechanism of plastic deformationPrimary mechanism of p
25、lastic deformationn nEntire planes of atoms move relative to one Entire planes of atoms move relative to one anotheranotherSlip Systemsn nSlip Slip uuSlip occurs on close-Slip occurs on close-packed planes in close-packed planes in close-packed directions(slip packed directions(slip systems)systems)
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