1 Metals Prepared by; Tuğba SARGIN 20519957 R.Özge ORDU 20519899 Tuğba SARGIN 20519957 R.Özge ORDU 20519899 Serhenk ÇELİK 20519613 Suat Armağan KOÇAK 20519828

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MetalsMetalsPrepared byPrepared by;; Tuğba SARGIN 20519957 Tuğba SARGIN 20519957

R.Özge ORDU 20519899R.Özge ORDU 20519899Serhenk ÇELİK 20519613Serhenk ÇELİK 20519613

Suat Armağan KOÇAK 20519828Suat Armağan KOÇAK 20519828

KMU-479 Material Science KMU-479 Material Science and Technology IIand Technology II

Department of Chemical EngineeringDepartment of Chemical EngineeringHacettepe UniversityHacettepe University

11.11.200911.11.2009

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OutlineOutlineStructure of Metals:Structure of Metals:-The crystal structure of metals. -The crystal structure of metals.

Mechanical Properties:Mechanical Properties: -Typical mechanical properties of metals.-Typical mechanical properties of metals.

Processing:Processing:-How metals are made into useful products.-How metals are made into useful products.

Alloys: Alloys: -What is an alloy?-What is an alloy?

Corrosion: Corrosion: -The conditions and chemistry of corrosion. -The conditions and chemistry of corrosion.

Metal Ores: Metal Ores: -How metals are removed from their ore. -How metals are removed from their ore.

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Metals at a GlanceMetals at a Glance

Regular, crystalline order of atoms,Regular, crystalline order of atoms,- makes - makes themthem distinguished from others. distinguished from others.

Metallic bond,Metallic bond,- as a chemical bonding type.- as a chemical bonding type.

Crystal structure,Crystal structure,- densely, regular, well-ordered structure.- densely, regular, well-ordered structure.

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Structure of MetalsStructure of Metals

Mathematically, a crystal can be considered as a three-Mathematically, a crystal can be considered as a three-dimensional arrangement of points (i. e., a lattice of dimensional arrangement of points (i. e., a lattice of points) that looks identical from each of the points. points) that looks identical from each of the points.

Figure adopted from Mechanical Figure adopted from Mechanical BehaviorBehavior of Engineering Materials, Springer Publications. of Engineering Materials, Springer Publications.

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There are 14 different possibilities to arrange atoms on a There are 14 different possibilities to arrange atoms on a lattice so that the lattice looks the same from each lattice lattice so that the lattice looks the same from each lattice point. These are called point. These are called Bravais latticesBravais lattices..

Figure adopted from Mechanical Behavior of Engineering Materials, Springer Publications.Figure adopted from Mechanical Behavior of Engineering Materials, Springer Publications.

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The 14 Bravais lattices can be grouped into seven The 14 Bravais lattices can be grouped into seven crystal systems according to their symmetry. crystal systems according to their symmetry.


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Each crystal system is characterized by six numbers: Each crystal system is characterized by six numbers: three lattice constants;three lattice constants;- indicating the edge lengths of the three axes making up - indicating the edge lengths of the three axes making up the unit cell, and the three angles between these axes.the unit cell, and the three angles between these axes.

Typical values of the lattice constant in metals are Typical values of the lattice constant in metals are between 0.2 nm and 0.6 nm. between 0.2 nm and 0.6 nm.

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In metals, three lattice structures are especially frequent. In metals, three lattice structures are especially frequent. Two of these are Bravais lattices with cubic symmetry:Two of these are Bravais lattices with cubic symmetry:

+ face centered cubic,+ face centered cubic,+ body centered cubic,+ body centered cubic,- hexagonal close-packed structure.- hexagonal close-packed structure.

Hexagonal close-packed structure is not a Bravais lattice Hexagonal close-packed structure is not a Bravais lattice as not all atoms occupy identical positions. as not all atoms occupy identical positions.

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a) Face-centered cubic.a) Face-centered cubic. b) Body-centered cubicb) Body-centered cubic c) Hexagonal Close-c) Hexagonal Close-Packed StructurePacked Structure


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→ →

→ →

(a) Hexagonal close-packed lattice.

(b) Face-centered cubic lattice. Figure adopted from Mechanical Behavior of Engineering Materials, Springer Figure adopted from Mechanical Behavior of Engineering Materials, Springer Publications.Publications.

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Periodic table of most known elements by crystal structures.Periodic table of most known elements by crystal structures.


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Mechanical Properties of MetalsMechanical Properties of Metals

StiffnessStiffness - Elastic Modulus or Young’s Modulus - Elastic Modulus or Young’s Modulus (MPa)(MPa)

StrengthStrength - Yield, Ultimate, Fracture, Proof, Offset - Yield, Ultimate, Fracture, Proof, Offset Yield. Measured as stress (MPa)Yield. Measured as stress (MPa)

HardnessHardness - Resistance to abrasion (Various - Resistance to abrasion (Various scales, e.g.; Rockwell, Brinell, Vickers.)scales, e.g.; Rockwell, Brinell, Vickers.)

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DuctilityDuctility - Measure of ability to deform plastically - Measure of ability to deform plastically without fracture - Elongation, Area Reduction, without fracture - Elongation, Area Reduction, Fracture Strain - (no units or mm/mm)Fracture Strain - (no units or mm/mm)

ToughnessToughness - - Resilience - Measure of ability to Resilience - Measure of ability to absorb energy (absorb energy (J/m3).).

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Stress Strain Curve for AluminumStress Strain Curve for Aluminum

(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

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Stress and StrainStress and Strain

In a simplistic sense, In a simplistic sense, stressstress may be thought of may be thought of as Load/Area.as Load/Area.

Similarly, Similarly, strainstrain is the deformation of the is the deformation of the component/original length.component/original length.

A stress may be direct, shear, or torsion - A stress may be direct, shear, or torsion - leading to corresponding deformations.leading to corresponding deformations.

Stress cannot be measured directly, but Stress cannot be measured directly, but deformation can be.deformation can be.

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Modulus of ElasticityModulus of Elasticity

Introduction To Materials Science, Chapter 6, Mechanical Properties of Metals, University of Tennessee, Dept. of Materials Science and Engineering

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Elastic DeformationElastic Deformation


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Plastic DeformationPlastic Deformation


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Yield StrengthYield Strength


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DuctilityDuctility


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Processing of MetalsProcessing of Metals

In industry, molten metal is cooled to form In industry, molten metal is cooled to form the solid. the solid.

The solid metal is then mechanically The solid metal is then mechanically shaped to form a particular product. shaped to form a particular product.

How these steps are carried out is very How these steps are carried out is very important.important.

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Grain Size EffectGrain Size Effect

Properties of some metals could be Properties of some metals could be changed by heat treating. changed by heat treating.

Grains in metals tend to grow larger as the Grains in metals tend to grow larger as the metal is heated. metal is heated.

Metals with small grains are stronger but Metals with small grains are stronger but they are less ductile. they are less ductile.

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AnnealingAnnealing

Annealing is a softening process in which Annealing is a softening process in which metals are heated and then allowed to metals are heated and then allowed to cool slowly.cool slowly.

Most steels may be hardened by heating Most steels may be hardened by heating and quenching (cooling rapidly). and quenching (cooling rapidly).

Metals are quenched in water or oil. Metals are quenched in water or oil.

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Quenching results in a metal that is very Quenching results in a metal that is very hard but also brittle. hard but also brittle.

Gently heating a hardened metal and Gently heating a hardened metal and allowing it to cool slowly will produce a allowing it to cool slowly will produce a metal that is still hard but also less brittle. metal that is still hard but also less brittle.

This process is known as tempering. This process is known as tempering.

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Cold WorkingCold Working

Plastic deformation results from the Plastic deformation results from the movement of dislocations. movement of dislocations.

Metals can be strengthened by preventing Metals can be strengthened by preventing this motion. this motion.

When a metal is bent or shaped, When a metal is bent or shaped, dislocations are generated and move. dislocations are generated and move.

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This will strengthen the metal, making it This will strengthen the metal, making it harder to deform. harder to deform.

This process is known as cold working.This process is known as cold working.

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What is Alloy?

Metal alloys are mixtures of two or Metal alloys are mixtures of two or more metallic elements or of metallic more metallic elements or of metallic and non-metallic elements.and non-metallic elements.

The elements either fuse together on a The elements either fuse together on a molecular level or dissolve into each molecular level or dissolve into each other when they are molten.other when they are molten.

Figures adopted from forum.donanımhaber.com

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Alloy PropertiesAlloy Properties

Give them special qualities such as corrosion resistance, Give them special qualities such as corrosion resistance, greater hardness or more strength. greater hardness or more strength.

Held together by the metallic bond.Held together by the metallic bond.

The atoms are the same size and slip over each other if The atoms are the same size and slip over each other if too much force is applied.too much force is applied.

Made up of atoms of different configurations, which Made up of atoms of different configurations, which helps prevent atom dislocations from weakening the helps prevent atom dislocations from weakening the metal.metal.

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Types of Alloys

Aluminum alloys Aluminum alloys

Copper alloys Copper alloys

Steel alloys Steel alloys

Gold alloys Gold alloys

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ExamplesExamples•Duralumin is an aluminum alloy (an Duralumin is an aluminum alloy (an alloy of Al, Cu, Mn, and Mg), alloy of Al, Cu, Mn, and Mg), •aircraft parts and tools aircraft parts and tools •it's lightweight and resistant to it's lightweight and resistant to corrosion.corrosion.

•Copper alloys include brass and Copper alloys include brass and bronze (Cu and Zn)bronze (Cu and Zn)•coin making, medals, electrical coin making, medals, electrical fittings and other hardware.fittings and other hardware.

Figures adopted from forum.donanimhaber.com

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ExamplesExamples

Figures adopted from forum.donanımhaber.com

•Stainless steel is a steel alloy Stainless steel is a steel alloy (an alloy of Fe and Cr)(an alloy of Fe and Cr)• lustrous and corrosion-lustrous and corrosion-resistantresistant•automobile parts, tools, automobile parts, tools, chemical and petrochemical chemical and petrochemical plant plant

• 24-karat gold is pure gold 24-karat gold is pure gold while 10- or 18-karat gold is while 10- or 18-karat gold is made by alloying gold with other made by alloying gold with other metals, such Ni, Cu, Ag or Ti.metals, such Ni, Cu, Ag or Ti.

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ChangesChanges

More attractive appearance or more strength.More attractive appearance or more strength. Density, reactivity, and electrical and thermal Density, reactivity, and electrical and thermal conductivity is similarconductivity is similar

Tensile strength and shear stress is differentTensile strength and shear stress is different

Melting rangeMelting range

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CorrosionCorrosion

Corrosion is a chemical Corrosion is a chemical change, in which a change, in which a metal loses its properties metal loses its properties because of a chemical because of a chemical reaction with its reaction with its environment.environment.

Figure adopted from www.materialsengineer.com

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CorrosionCorrosion

Corrosion is a very slow process.Corrosion is a very slow process.

Corrosion Corrosion behaviorbehavior different for different for different types of metals. different types of metals.

figure adoted from www.materialsengineer.com

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Types of CorrosionTypes of Corrosion

– GeneralGeneral– LocalizedLocalized– GalvanicGalvanic– Environmental CrackingEnvironmental Cracking

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General CorrosionGeneral Corrosion

Figure is adopted from www.iitb.ac.in/~corrsci/uniform2.jpg

The surface effect produced by most direct chemical attacks (e.g., as by an acid) is a uniform etching of the metal.

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Localized CorrosionLocalized Corrosion

Figure adopted from www.corrosionsource.com

It occurs at distinct locations, usually small when compared to the entire surface area of the metal. Often caused by chemical or physical differences of local cells on metal.

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Types of Localized CorrosionTypes of Localized Corrosion

Pitting CorrosionPitting Corrosion

Pitting corrosion takes the formPitting corrosion takes the form

of deep and narrow corrosiveof deep and narrow corrosive

attack, which often causes rapidattack, which often causes rapid

penetration of the wall thicknesspenetration of the wall thickness..

Crevice CorrosionCrevice Corrosion

Crevice or contact corrosion is theCrevice or contact corrosion is the

corrosion produced at the regioncorrosion produced at the region

of contact of metals with metals orof contact of metals with metals or

metals with nonmetals.metals with nonmetals.

Figures adopted from corrosion.ksc.nasa.gov

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Galvanic CorrosionGalvanic Corrosion

Galvanic corrosion is an Galvanic corrosion is an electrochemical action of electrochemical action of two dissimilar metals in two dissimilar metals in

the presence of an the presence of an electrolyte. It occurs when electrolyte. It occurs when

dissimilar metals are in dissimilar metals are in

contactcontact. . Figure adopted from www.nasa.gov.tr

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Environmental CrackingEnvironmental Cracking

Environmental Environmental cracking is caused cracking is caused by the combined by the combined action of a tensile action of a tensile stress and corrosionstress and corrosion

Figure adopted from www.nasa.gov.tr

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Types of Environmental CrackingTypes of Environmental Cracking

• Stress Corrosion CrackingStress Corrosion Cracking

• Hydrogen Induced CrackingHydrogen Induced Cracking

• Liquid Metal CrackingLiquid Metal Cracking

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Stress Corrosion CrackingStress Corrosion Cracking

is caused by the same effects of is caused by the same effects of tensile stress and a specific tensile stress and a specific

corrosive environmentcorrosive environment. .

Figure adopted from www.nasa.gov

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Hydrogen Induced CrackingHydrogen Induced Cracking

Caused by the combined action of a Caused by the combined action of a tensile stress and hydrogen trapped in tensile stress and hydrogen trapped in the metal the metal

Figure adopted from www.nasa.gov

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Liquid Metal CrackingLiquid Metal Cracking

A form of embrittlement that A form of embrittlement that results from the combined results from the combined action of a tensile stress and action of a tensile stress and a liquid metal in contact with a liquid metal in contact with the alloy surfacethe alloy surface

Figure adopted from www.nasa.gov.tr

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How to Prevent Corrosion?How to Prevent Corrosion?

• Select products made of nonSelect products made of non--corrosive metalscorrosive metals• Apply coatings like inorganic paints Apply coatings like inorganic paints • ElectroplatingElectroplating• Metal SprayingMetal Spraying• Surface TreatmentSurface Treatment• AnodizingAnodizing

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Metal OresMetal Ores

• Mineral occurs naturally in Earth’s crustMineral occurs naturally in Earth’s crust

• Mineral contains high percentage of a metal for Mineral contains high percentage of a metal for economic extractioneconomic extraction

• Metal ores are generally oxides, sulfides, silicates…Metal ores are generally oxides, sulfides, silicates…

• Gold,Gold, Platinum,Platinum, Silver and Copper,Silver and Copper, Bauxite (AlBauxite (Al22OO33))

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Manganese ore Gold ore Lead ore

Figures adopted from the www.en.wikipedia.org

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How metal removed from their How metal removed from their ores?ores?

There are three basic ways :There are three basic ways :

PyroPyro--metallurgy,metallurgy, includes roastingincludes roasting

Electrometallurgy, the metals are processed using Electrometallurgy, the metals are processed using electricity such as electroplating and electro refining.electricity such as electroplating and electro refining.

HydrometallurgyHydrometallurgy which which is a wet processis a wet process..

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SummarySummaryStructure of MetalsStructure of Metals - - Structures of well known metals - - Structures of well known metals

Mechanical Properties of MetalsMechanical Properties of Metals- Toughness, ductility etc.- Toughness, ductility etc.

ProcessingProcessing of Metals of Metals- Annealing, cold working.- Annealing, cold working.

AlloysAlloys More physical properties to metalsMore physical properties to metals

CorrosionCorrosion General, localized, galvanic, environmental crackingGeneral, localized, galvanic, environmental cracking

OreOre- Pyrometallurgy- Pyrometallurgy- Electrometallurgy- Electrometallurgy- Hydrometallurgy- Hydrometallurgy

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References References

Mechanical Behavior of Engineering Materials Mechanical Behavior of Engineering Materials

The Science and Engineering Materials The Science and Engineering Materials

www.wikipedia.orgwww.wikipedia.org

www.nasa.govwww.nasa.gov

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Questions?Questions?

Documents

1 Metals Prepared by; Tuğba SARGIN 20519957 R.Özge ORDU 20519899 Tuğba SARGIN 20519957 R.Özge ORDU 20519899 Serhenk ÇELİK 20519613 Suat Armağan KOÇAK 20519828