材料概论复习资料1docWord文档格式.docx
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Natureofchemicalbonds
原子或分子在空间的排列分布和运动规律,
Atomicordering
原子集合体的形貌特征。
Microstructure
PropertiesofMaterials
Mechanicalproperties:
Thebehaviorofmaterialsdeformedbyaset
offorces・
弹性Elasticity
塑性Plasticity
强度Strength
硬度Hardness
韧性Toughness
疲劳牛寺性Fatiguebehaviour
而寸磨性Abrasionresistance
Classificationofmaterials:
basedonatomicstructuresandthenatureofbonds
Metalsandtheiralloys
Organicpolymers
Ceramics
Mechanicalproperties:
whichreflectthebehaviorofmaterialsReformedbyasetofforces
Physicalproperties:
whichdescribethebehaviorofmaterialssubjectedtotheactionoftemperature^electricormagneticfields9orlight・
Chemicalproperties:
whichcharacterizethebehaviorofmaterialinareactiveenvironment.
Performances
Structure
Typesofmaterials
1metalitisstrongandcanbereadilyformedintopracticalshapes.itsextensive,permanentductilityisanimportantassetinpermittingsmallamountsofyieldingtosuddenandsevereloads・
2ceramicsandglasses
Chemicalstable,siginificantlyhighermeltingpoint,brittleness
3polymerspolymersarefrequentlylightweightJowcostJowerstrength」owermeltingpointand
higherchemicalreactivity
4compositesitcarriesalongthesuperiorpropertiesofeachcomponent,producingaproductthatissuperiortoeitherofthecomponentsseparately
Solidsexistinthenatureintwoprincipalforms:
crystallineandamorphous
Anelementarycellofcrystallatticeisdescribed
Threesectionsa,b,andc,
Threeanglesmadeby
eachtwoofthesesections,
q,B,andy・
晶格常数latticeconstant/
latticespacing:
a>
b、c.
crystalstructure:
body-centeredcubicstructure,face-centeredcubicstructure,hexagonalclose-packedstructure
thepropertiesofcrystalsaredifferentinvariouscrystallographicdirections,whichareassociatedwithan
orderedarrangementofatomsinspace.
AdvantagesofMetals
Strong
Soft:
Cutting,Machining,Shaping
Meltingandcasting
Heatconductive
Electricconductive
Light-Reflective
Ironconsistofslagandcarbon9butsteelconsistofmanyelementsuchascarbon^silicon^manganese,nickelandsoon.
Thetypesofcastiron;
whitecastiron,graycastiron,alloycastiron,nodularorductilecastiron,malleablecastironAluminum
Rustresistant
Highreflectivity
Canbediecast
Easilymachined
Goodformability
Nonmagnetic
Nontoxic
One-thirdthestiffnessofsteel
Onethirdoftheweightofsteel
Goodthermalandelectricalconductivity
Highstrength-to-weightratio
Canbegivenahardsurfacebyanodizingandhardcoating
Mostalloysareweldable
Copperanditsalloys:
copper,brassandbronze
Magnesium
Thelightestofallstructuralmetals
Specificgravity:
1.75
Magnesiumweighs1.5timeslessthan
anequalvolumeofaluminumand4times
lessthanzinc.
Highstrength,stiffness,dimensional
stability,
Alloyshave
Relativelyhighthermalandelectrical
conductivities;
Goodenergyabsorptioncharacteristics;
Nonmagneticproperties
Mechanicalproperties
Forbasictypesofstresses:
tensile,compressive,
shear^torsion
(拉力,压力,剪切力,扭转力)
Strength:
thestrengthofametalisitsabilitytoresistchangingitsshapeorsizewhenexternalforcesareapplied.
Elasticity:
theabilityofamaterialtostrainunderloadandthenreturntoitsoriginalshapeandsizewhenunloaded.
Yieldpoint:
yieldingorplasticflowoccursinmaterialswhentheelasticlimithasbeenexceeded・
Plasticity:
metalsundergoplasticflowwhenstressedatorbeyondtheirelasticlimits•
Brittleness:
amaterialthatwillnotdeformplasticallyissaidtobebrittle.
Stiffness:
stiffnessisexpressedbythemodulusofelasticity.Ductility:
thepropertythatallowsametaltodeformpermanentlywhenloadedintension•
Astemperaturedecreases,thestrength^hardness,andthemodulusofelasticityincreaseforalmostallthemetals.Metalsandnonmetals
Abilitytodonateelectronsandformapositive
ion
Crystallinestructure
Highthermalandelectricalconductivity
Abilitytobedeformedplastically
Metallicluster(光泽)orreflectivity
Body-centeredcubic:
columbium,barium,vanadium,(^nj,令贝,机)Face-centeredcubic:
calcium,aluminum,copper,lead,nickel,goldHexagonalclose-packed:
zinc,titanium,magnesium
Thereareseveralwaystoprotectagainstcorrosion.Corrosioncanbepreventedorlessenedby
Coatings,
Designconsiderations,
Environmentalcontrol,
Alloying,amongothers
Ceramiccompounds:
Canbedefinedasinorganiccompoundsmadebyheatingclayorothermineralmattertoahightemperatureatwhichtheypartia
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