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INTRODUCTION TO MATERIALS

CHAPTER 1

Dr. Ir. M. Sabri, [email protected] +60162931775

mailto:[email protected]

mailto:[email protected]



Introduction to Material

Learning Objectives:To define raw materialsTo define engineering materials

To classify the engineering materials into differentgroupsTo explain the semi-finished productsTo explain the machining involved to produce Finish

productsTo explain the flow of materials to final productTo explain the importance of standards parts.




Raw MaterialsUnprocessed natural products used in manufacture.

Unfinished good used in the manufacture of a product.

Examples:Iron Ores

Woods

Crude oil

Coal

http://images.google.com.my/imgres?imgurl=http://www.hse.k12.in.us/staff/sking/elements/2/iron/iron-ore-closeup.jpg&imgrefurl=http://www.hse.k12.in.us/staff/sking/elements/2/iron/iron.htm&h=345&w=520&sz=126&hl=en&start=0&tbnid=bpC3dLQhT4QhQM:&tbnh=87&tbnw=131&prev=/images?q=iron+ore&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://img.alibaba.com/photo/10784397/Iron_Ore_66_56__Fe__64_5__Fe_Origin_Brazil.jpg&imgrefurl=http://www.alibaba.com/catalog/10784397/Iron_Ore_66_56_Fe_64_5_Fe_Origin_Brazil.html&h=405&w=540&sz=30&hl=en&start=0&tbnid=hnB9LgC0gL54VM:&tbnh=99&tbnw=132&prev=/images?q=iron+ore&gbv=2&svnum=10&hl=en&safe=off




Raw Material

EngineeringMaterial

Metals

Ferrous Non-Ferrous

Non-Metals

AuxiliaryMaterial




Engineering MaterialsRaw materials that has been processed into semi-finished products

Examples:Spare parts

Cast iron

Etc

http://images.google.com.my/imgres?imgurl=http://www.maseratipreowned.com/graphics/genuine_spare.jpg&imgrefurl=http://www.maseratipreowned.com/genuine_spare_parts.php&h=415&w=485&sz=41&hl=en&start=0&tbnid=hlwtGU029ygSWM:&tbnh=110&tbnw=129&prev=/images?q=spare+parts&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://www.roslerusa.com/www_roeslerus2006/images/niederlassung_usa/Service/spare_parts_service_01.jpg&imgrefurl=http://www.roslerusa.com/www_roeslerus2006/spare_parts_2918_623_6_f.htm?query=&h=300&w=450&sz=29&hl=en&start=0&tbnid=BVgc88dzqJF1SM:&tbnh=85&tbnw=127&prev=/images?q=spare+parts&gbv=2&svnum=10&hl=en&safe=off




MetalsFerrous (presence of iron element inside the material)

Steel

Cast ironNon-ferrous

Copper

Zinc

Tin

http://images.google.com.my/imgres?imgurl=http://www.highenergymetals.com/Al-SS_Ring_Hydrogen_tank.jpg&imgrefurl=http://www.highenergymetals.com/&h=411&w=475&sz=21&hl=en&start=0&tbnid=gCS4mgzjqXOeLM:&tbnh=112&tbnw=129&prev=/images?q=metals&gbv=2&svnum=10&hl=en&safe=off




Non-metalsExist naturally or artificially produced (manufactured)

Wood

RubberResin

Polymer

Cotton

Asphalt sheets

http://images.google.com.my/imgres?imgurl=http://www.enchuan.com.tw/images/asphalt_sheet.jpg&imgrefurl=http://www.enchuan.com.tw/asphalt.htm&h=204&w=297&sz=5&hl=en&start=0&tbnid=Ncn9LsjoS2pIZM:&tbnh=80&tbnw=116&prev=/images?q=asphalt+sheet&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://www.acencorp.com/English/product/photo/NYLON1.jpg&imgrefurl=http://www.acencorp.com/English/products/product.asp?product_id=306&h=768&w=1024&sz=204&hl=en&start=0&tbnid=LNGwJiYnPLGFYM:&tbnh=113&tbnw=150&prev=/images?q=plastic+resin&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://www.made-in-china.com/image/2f0j00NUptYIQzoaPkM/Project-Tyre.jpg&imgrefurl=http://www.made-in-china.com/showroom/qingdaolutai/product-detailCAYxtLQUWnPc/China-Project-Tyre.html&h=360&w=360&sz=26&hl=en&start=0&tbnid=A9T5OvVWXjdSjM:&tbnh=121&tbnw=121&prev=/images?q=tyre&gbv=2&svnum=10&hl=en&safe=off




Materials

http://images.google.com.my/imgres?imgurl=http://www.legionglobal.net/images/superbike-559.jpg&imgrefurl=http://www.legionglobal.net/index.php&h=359&w=350&sz=55&hl=en&start=0&tbnid=QhOV2ySLHlbuFM:&tbnh=121&tbnw=118&prev=/images?q=superbike&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://www.teething-teeth.com/images/Baby-Food-Grinder-Food-Mill.jpg&imgrefurl=http://www.teething-teeth.com/baby-food-Grinder-Product.html&h=450&w=400&sz=39&hl=en&start=0&tbnid=cLI6Cs1uhjcC4M:&tbnh=127&tbnw=113&prev=/images?q=food&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://www.coe.ufrj.br/~acmq/mk92405.jpg&imgrefurl=http://www.coe.ufrj.br/~acmq/electrostatic.html&h=475&w=500&sz=31&hl=en&start=0&tbnid=c8f00V6SjtBUVM:&tbnh=123&tbnw=130&prev=/images?q=machines&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://artistsunite-ny.org/issue/images/sunday/DSC08861.jpg&imgrefurl=http://artistsunite-ny.org/blog/?m=200607&h=300&w=400&sz=65&hl=en&start=0&tbnid=tuLY-CKQNnZ5_M:&tbnh=93&tbnw=124&prev=/images?q=buidings&gbv=2&svnum=10&hl=en&safe=off

http://images.google.com.my/imgres?imgurl=http://www.corrosioncost.com/transportation/ships/ships2.jpg&imgrefurl=http://www.corrosioncost.com/transportation/ships/index.htm&h=533&w=800&sz=79&hl=en&start=0&tbnid=X0wlOF_VimGswM:&tbnh=95&tbnw=143&prev=/images?q=ships&gbv=2&svnum=10&hl=en&safe=off&sa=G

http://www.maniacworld.com/amazing-cars.jpg



Flow of Raw Material to Final Product

RAWMATERIAL

SEMI FINISHEDPRODUCTS

FINISHEDPRODUCT

FINAL

PRODUCT

AUXILIARY

MATERIAL

Processed into

Machined into

Assembled into




AssignmentFind one example of Finished Product and determinethe process flow to manufacture the product from raw

materials.Example:

Process flow to produce a book from paper and paper fromtrees.



11

Engineering materials

Dr. Ir. M. Sabri, MT



12

Classifications & Specifications of Metallic Materials

Major characteristics of metallic materials arecrystallinity, conductivity to heat and electricity andrelatively high strength & toughness.Classification: systematic arrangement or division ofmaterials into group on the basis of some commoncharacteristicGenerally classified as ferrous and nonferrous

Ferrous materials-iron as the base metal,

range from plain carbon (>98% Fe) to highalloy steel (<50% alloying elements)Nonferrous materials consist of the rest of themetals and alloys

Eg. Aluminum, magnesium, titanium & theiralloys

Metal / Metallic materials



13

Within each group of alloy, classification can bemade according

(a) chemical composition, e.g. carbon content oralloys content in steels;(b) finished method, e.g. hot rolled or coldrolled;(c) product form, e.g. bar, plate, sheet, tubing,structural shape;(d) method of production, e.g. cast, wroughtalloys.



14

Designation: identification of each class by anumber, letter, symbol, name or a combination.Normally based on chemical composition ormechanical properties.Example : Table 2.1 designation systems for steel

System used by AISI & SAE: 4, or 5 digits whichdesignate the alloy composition.

1st two digits indicate Alloy systemLast two or three digits nominal carbon contentin hundredths of a percent



15



16

In most eng. application, selection of metallic is usuallybased on the following considerations:1) Product shape: a) sheet, strip, plate, (b) bar, rod, wire,

(c) tubes, (d) forging (e) casting2) Mechanical properties-tensile, fatigue, hardness,creep,impact test

3) Physical & chemical properties-specific gravity, thermal& electrical conductivity, thermal expansion

4) Metallurgical consideration-anisotrophy of properties,hardenability of steel, grain size & consistency ofproperties

5) Processing castability-castability, formability,machinability

6) Sales appeal-color, luster7) Cost & availability



17

Design and selection for metalsOne of the major issues for structural componentsis deflection under service load.

A function of the applied forces and geometry,and also stiffness of material.Stiffness of material is difficult to change,either shape or the material has to be changed iforder to achieve a large change in the stiffnessof a component.



18

Load carrying capacity of component can be related

to the yield strength, fatigue strength or creepstrength depending on loading & service condition.All are structure sensitive.

Changed by changing chemical composition of the

alloy, method and condition of manufacturing, aswell as heat treatmentIncreasing the strength cause metal ductility &toughness to decrease which affects the

performance of component.



19

Electrical & thermal conductivities

Thermal conductivity, KIs measure of the rate at which heat istransferred through a material

Al & Cu- Manufacture of component where

electrical conductivity is primaryrequirementCorrosion resistance & specific gravity limitsthe materials.



20

Manufacturing considerationMajority of metallic components are wrought or castWrought m/str:

usually stronger and more ductile than cast.Available in many shapes & size tolerance

Hot worked products:

Tolerance are wider thus difficult for automaticmachiningPoor surface quality, esp. in sheet/wire drawing

Cold worked product:

Narrow toleranceResidual stress cause unpredictable size change duringmachining



21

Weldability – a function of material composition.So structure involve welding of the componentsneed to consider. Also for other joining means.Machinability:

Important if large amounts of material haveto be removedimprovement by heat treatment or alloyingelements

Economic aspects:material able to perform function at lowestcostPlain carbon steel & cast iron are the leastexpensive



22

Classifications of PolymersPolymer – low density, good thermal & electricalinsulation, high resistance to most chemicals andability to take colours and opacities.But unreinforced bulk polymer are mechanicallyweaker, lower elastic moduli & high thermalexpansion coefficients.Improvement Reinforced variety of fibrousmaterials Composites (PMC).

Design for polymer



23

Advantages : ease of manufacturing & versatility.Can manufacture into complicated shapes in one

step with little need for further processing orsurface treatment.Versatility : ability to produce accuratecomponent, with excellent surface finish andattractive color, at low cost and high speed

Application: automotive, electrical & electronicproducts, household appliance, toys, container,packaging, textilesBasic manufacturing processes for polymer partsare extrusion, molding, casting and forming ofsheet.



24

Thermoset & thermoplasticDiffer in the degree of their inter-molecularbondingThermoplastic-litle cross bonding betweenpolymer, soften when heated & harden whencooledThermoset-strong intermolecular bonding whichprevents fully cured materials from softeningwhen heated

Rubber are similar to plastic in structure and thedifference is largely based on the degree ofextensibility or stretching.



25

Design consideration for polymer

Structural part/When the parts is to carry load

Should remember the strength and stiffnessof plastics vary with temperature.

T room data cannot be used in design calculation

if the part will be used at other temp.Long term properties cannot be predicted from

short term prop. Eg. Creep behavior

Engineering plastics are britle (notched impactstrength < 5.4 J/cm)

Avoid stress raiser



26

Classification of Ceramic Materials

Ceramics – inorganic compounds of one or more metalswith a nonmetallic element. Eg Al 2O3, SiC, Si2N3.Crystal structure of ceramic are complex

They accommodate more than one element ofwidely different atomic size.The interatomic forces generally alternate

between ionic & covalent which leave few freeelectrons

usually heat & electrical insulators.Strong ionic & covalent bonds give high hardness,stiffness & stability (thermal & hostile env.).

Design for ceramics



27

Structure:

(1) Amorphous or glass-short range order, (2)crystalline (long range order) & (3) crystallinematerial bonded by glassy matrix.Clasiification:

Whitewares, glass, refractories, structural clayproducts & enamels.Characteristics:

Hard & brittleness,

low mechanical & thermal shockHigh melting pointsThermal conductivities between metal & polymer

f



28

Design consideration for ceramicsBritle, low mechanical & thermal shock-need specialconsideration

Ratio between tensile strength, modulus of rupture &compressive strength ~ 1:2:10. In design, load ceramicparts in compression & avoid tensile loadingSensitive to stress concentration

Avoid stress raiser during design.Dimensional change take place during drying and firing,should be considerLarge flat surface can cause wrappingLarge changes in thickness of product can lead tononuniform drying and cracking.Dimensional tolerances should be generous to avoidmachining



29

IntroductionA composite material can be broadly defined as anassembly two or more chemically distinctmaterial, having distinct interface between themand acting to produce desired set of properties

Composites – MMC, PMC & CMC.The composite constituent divided into two

Matrix

Structural constituent / reinforcement

Design for composite



30

Properties / behavior depends on properties, size& distribution, volume fraction & shape of theconstituents, & the nature and strength of bondbetween constituents.Mostly developed to improve mechanicalproperties i.e strength, stiffness, creepresistance & toughness.Three type of composite

(1) Dispersion-strengthened,

(2) Reinforcement – continuous & discontinuous(3) Laminated (consist more than 2 layersbonded together).



31



32

Designing with compositeA composite materials usually are more expensive ona cost.Used when weight saving is possible when therelevant specific property (property/density) of thecomposite is better than conventional material

E.g. specific strength (strength/density), specificelastic modulus ( elastic modulus/density)Efficient use of composite can be achieved bytailoring the material for the application

E.g., to achieve max. strength in one direction in afibrous composite, the fibers should be wellaligned in that direction



33

If composite is subjected to tensile loading,important design criterion is the tensile

strength in the loading directionUnder compression loading, failure by bucklingbecome important

Fatigue behavior:Steel- show an endurance limit or a stressbelow which fatigue does not occurComposite-fatigue at low stress level becausefibrous composites may have many crack, whichcan be growing simultaneously and propagatethrough the matrix



1 STEEL• 1.1 Iron-carbon compounds

• 1.2 Microstructure of steels

• 1.3 Manufacturing and forming processes

• 1.4 Mechanical properties

• 1.5 Steels for different applications

• 1.6 Joints in steel



Definitions•Iron… A chemical element (Fe)

•Ion… A charged particle, e.g. Cl - or Fe ++

Iron is an element with the chemical symbol Fe. Steel and cast

iron are described as "ferrous" metals and are made from ironwith different carbon contents.



Carbon contents

Carbon Content Material 0.02% Wrought Iron - no longer

generally available in the UK

0.15% Low carbon steel

0.15-0.25% Mild and high yield steels

0.5-1.5% High carbon and tool steels

3-4% Cast irons



Ironbridge



3.1 STEEL• 3.1.1 Iron-carbon compounds

• 3.1.2 Microstructure of steels

• 3.1.3 Manufacturing and forming processes

• 3.1.4 Mechanical properties

• 3.1.5 Steels for different applications

• 3.1.6 Joints in steel



MICROSTRUCTURAL EFFECTSON STRENGTH

CARBON CONTENT

CONTROL OF GRAIN SIZE• Control by Heating• Control by Working• Control by Alloying



Face centred cubic and Body centred cubic



Volume change on heatingsteel



The nomenclature is:

• FERRITE or Fe : This is the bcc iron which isformed on slow cooling and may contain up to0.08% Carbon . Soft, ductile and not particularlystrong.

• CEMENTITE: This is iron carbide which containsabout 6.67% Carbon.

• PEARLITE: This in the laminar mixture of ferriteand cementite and has an average carbon content

of about 0.78%. Hard, brittle and strong• AUSTENITE or Fe: This is the fcc iron which isformed at high temperatures and may contain upto 2%C

Ph



Phasediagram forsteel(iron/carbon

)



Strengths andcarbon

contents of steels



High

carboncontent.Low

elongationvalue.Low impact resistance.Brittlefailure.




CARBON CONTENT

CONTROL OF GRAIN SIZE

• Control by Heating

• Control by Working

• Control by Alloying



Movement of dislocation 1

GrainBoundary




GrainBoundary




GrainBoundary

Effect of ferrite grain size on the ductile/brittle



Effect of ferrite grain size on the ductile/brittletransition temperature for mild steel

P fl id i di ft t il f il Th



Pore fluid expression die after tensile failure. Theinner core has fractured but the outer shell is a lessbrittle steel so there was no explosive failure.

MICROSTRUCTURAL EFFECTS




CARBON CONTENT

CONTROL OF GRAIN SIZE• Control by Heating



C li S l f Hi h



Cooling Steel from HighTemperatures• Slow Cooling (annealing) gives large grain size – ductile steel

• Cooling in air (normalising) gives smaller grains

• Rapid cooling in water (quenching) gives hard brittle steel

art o ron car on p ase



art o ron car on p asediagram

C li St l f Hi h



Cooling Steel from HighTemperatures• Slow Cooling (annealing) gives large grain size – ductile steel

• Cooling in air (normalising) gives smaller grains

• Rapid cooling in water (quenching) gives hard brittle steel



carbon

content onhardnessforproducts of rapidcooling(martensite

and





CARBON CONTENT






Early cold worked steel





CARBON CONTENT






Rolling sequence

for steel angle

Rolled steel



sections•RSC Rolled Steel Column•UB Universal Beam

•RSA Rolled Steel Angle

• RST Rolled steel T

•RHS Rolled Hollow Section



The RSJ

• The UB has parallel flanges. A limited number of traditional RSJs(Rolled Steel Joists) with tapered flanges are produced insmaller section sizes.

Web

Flange

RSJ Flange UB



Stress-Strain curves



Stress-Strain curve for steel

Yield

Elastic

0.2%

proof stress

Stress

Strain0.2%

Plastic

Failure



Embrittlement at cold temperatures



S-N curves for fatigue



3.1 STEEL• 3.1.1 Iron-carbon compounds• 3.1.2 Microstructure of steels



• 3.1.5 Steels for different applications • 3.1.6 Joints in steel

e propert es requ re o



e propert es requ re ostructural steels are:

• Strength. This is traditionally specified as a characteristic valuefor the 0.2% proof stress

• Ductility to give impact resistance. Ductility increases withreducing carbon content.

• Weldability. (see below).



Steelframe (1)



Steel frame (2)



Steel frame (3)



Steel

structure

Light



Light weight steel



Steel Framedhousing



HousingDetails



Steel in

masonrystructure



Steel Bridge



Reinforcing Steels

• Reinforcing steels are tested for strength and must alsocomply with the requirements of a "rebend" test to ensurethat they retain their strength when bent to shape. This limitsthe carbon content. High yield bars are cold worked.



Bending Reinforcement



Prestressing steels

• Prestressing steels (high tensile steels) are not bent so theycan have higher carbon contents that normal reinforcementand have higher strengths. This limits the ductility but isnecessary to avoid loss of prestress due to creep



Prestresse

d slabs



Pre-

stressing

systems



3.1 STEEL

• 3.1.1 Iron-carbon compounds• 3.1.2 Microstructure of steels



• 3.1.5 Steels for different applications• 3.1.6 Joints in steel

e ma n me o s o we ng



gare:

• Gas welding . In order to produce a hot enoughflame a combustible gas (e.g. acetylene) is burnt

with oxygen. This method is not used for majorwelding jobs but has the advantage that the torchwill also cut the metal.

• Arc welding . In this method a high electric currentis passed from the electrode (the new metal forthe weld) to the parent metal. The electrode iscoated with a "flux" which helps the weldformation and prevents contact with air whichwould cause oxide and nitride formation.

• Inert gas shielded arc welding . This method usesa supply of inert gas (often argon) to keep the airoff the weld so no flux is needed.



Gas and Arc welding

General points about welding.



p g• Do not look directly at a welding process (especially

electric arc). It may damage your eyes.

• Always allow for the effect of heating anduncontrolled cooling of the parent metal. e.g. if highyield reinforcing bar is welded the effect of the coldworking will be lost - and with it much of thestrength. This heating will also often cause distortion.

• Check the welding rods. If they have become dampthe flux will be damaged. Use the correct rods for thesteel (e.g. stainless).

• Remember that the welding process cuts into theparent metal and, if done incorrectly, may causesubstantial loss of section.



OTHER JOINTING SYSTEMS

• Bolted Joints• Rivets



Rivets and bolts

Riveting the Empire State



g pBuilding



Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Metal Alloys: Structure andStrengthening by Heat Treatment




Gear Teeth Cross-section

Figure 4.1 Cross-section of gear teeth showing induction-hardenedsurfaces. Source: Courtesy of TOCCO Div., Park-Ohio Industries, Inc.

Ch 4 T i




Chapter 4 Topics

Figure 4.2 Outline of topics described in Chapter 4.

T Ph S




Two Phase Systems

Figure 4.3 (a) Schematic illustration of grains, grain boundaries, and particles dispersedthroughout the structure of a two-phase system, such as a lead-copper alloy. The grainsrepresent lead in solid solution in copper, and the particles are lead as a second phase.(b) Schematic illustration of a two-phase system consisting of two sets of grains: darkand light. The dark and the light grains have separate compositions and properties.

C li f M l




Cooling of Metals

Figure 4.4 (a) Cooling curve for the solidification of pure metals. Note that freezingtakes place at a constant temperature; during freezing, the latent heat of solidification is given off. (b) Change in density during the cooling of pure metals.

Ph Di f Ni k l All S t




Phase Diagram for Nickel-copper Alloy System

Figure 4.5 Phase diagram for nickel-copper alloy system obtained at a slow rate of solidification. Note that pure nickel and pure copper each has one freezing or melting temperature. The top circle on the right depicts the nucleation of crystals.The second circle shows the formation of dendrites (see Section 10.2). The bottomcircle shows the solidified alloy with grain boundaries.

Mechanical Properties of Copper Alloys




Figure 4.6 Mechanical properties of copper-nickel and copper-zincalloys as a function of their composition. The curves for zinc are short,because zinc has a maximum solid solubility of 40% in copper.

L d ti Ph Di g




Lead-tin Phase Diagram

Figure 4.7 The lead-tin phase diagram. Note that the composition of eutecticpoint for this alloy is 61.9% Sn – 38.1% Pb. A composition either lower or higher than this ratio will have a higher liquidus temperature.

Iron iron Carbide Phase Diagram




Iron-iron Carbide Phase Diagram

Figure 4.8 The iron-iron carbide phase diagram. Because of the importance of steel as an engineering material, thisdiagram is one of the most important of all phase diagrams.

Unit Cells




Unit Cells

Figure 4.9 The unit cells for (a) austenite, (b) ferrite, and (c) martensite. The effectof percentage of carbon (by weight) on the lattice dimensions for martensite isshown in (d). Note the interstitial position of the carbon atoms (see Fig. 1.9). Alsonote, the increase in dimension c with increasing carbon content: this effect causesthe unit cell of martensite to be in the shape of a rectangular prism.

Microstructures for an Iron Carbon Alloy




Microstructures for an Iron-Carbon Alloy

Figure 4.10 Schematic illustration of the microstructures for an iron-carbon alloy of eutectoidcomposition (0.77% carbon) aboveand below the eutectoid temperatureof 727 °C (1341 °F).

Microstructure of Steel Formed from Eutectoid Composition




Microstructure of Steel Formed from Eutectoid Composition

Figure 4.11 Microstructure of pearlite in 1080 steel formed from austeniteof a eutectoid composition. In this lamellar structure, the lighter regionsare ferrite, and the darker regions are carbide. Magnification: 2500x.

Iron Carbon Phase Diagram with Graphite




Iron-Carbon Phase Diagram with Graphite

Figure 4.12 Phase diagram for the iron-carbon system with graphite (instead of cementite) as the stable phase. Note that this figure is an extended version of Fig. 4.8.

Microstructure for Cast Irons




Microstructure for Cast Irons

Figure 4.13 Microstructure for cast irons. Magnification: 100x. (a) Ferritic gray ironwith graphite flakes. (b) Ferritic ductile iron (nodular iron) with graphite in nodular form. (c) Ferritic malleable iron. This cast iron solidified as white cast iron with thecarbon present as cementite and was heat treated to graphitize the carbon.

Microstructure of Eutectoid Steel




Microstructure of Eutectoid Steel

Figure 4.14Microstructure of eutectoidsteel. Spheroidite is

formed by tempering thesteel at 700 °C (1292 °F).Magnification: 1000x.

Martensite




Figure 4.15 (a) Hardness of martensite as a function of carbon content. (b)Micrograph of martensite containing 0.8% carbon. The gray plate-like regions aremartensite; they have the same composition as the original austenite (whiteregions). Magnification: 1000x.

Hardness of Tempered Martensite




Figure 4.16 Hardness of tempered martensite as a function of tempering time for the 1080 steel quenched to 65 HRC. Hardnessdecreases because the carbide particles coalesce and grow in size,thereby increasing the interparticle distance of the softer ferrite.

Time-temperature




temperature-transformation

diagrams

Figure 4.17 (a) Austenite-to-pearlite transformation

of iron-carbon alloy as afunction of time andtemperature. (b)Isothermal transformationdiagram obtained from (a)for a transformationtemperature of 675 °C(1274 °F). (c)Microstructures obtainedfor a eutectoid iron-carbonalloy as a function of cooling rate.

Hardness and Toughness in Steel as a Function of Carbide Shape




Hardness and Toughness in Steel as a Function of Carbide Shape

Figure 4.18 (a) and (b) Hardness and (c) toughness for annealed plain-carbon steel as afunction of a carbide shape. Carbides in the pearlite are lamellar. Fine pearlite is obtainedby increasing the cooling rate. The spheroidite structure has sphere-like carbide particles.

Mechanical Properties of Steel as a Function of




Composition and Microstructure

Figure 4.19 Mechanical properties of annealed steels as a function of composition andmicrostructure. Note in (a) the increase in hardness and strength and in (b) the decreasein ductility and toughness with increasing amounts of pearlite and iron carbide.

End Quench




End-QuenchHardenability

Test

Figure 4.20 (a) End-quench test and cooling

rate. (b) Hardenabilitycurves for five differentsteels, as obtained from theend-quench test. Smallvariations in compositioncan change the shape of these curves. Each curve isactually a band, and itsexact determination isimportant in the heattreatment of metals for better control of properties.

Phase Diagram for Aluminum-copper Alloyand Obtained Microstructures




Figure 4.21 (a) Phase diagram for the aluminum-copper alloy system.(b) Various microstructures obtained during the age-hardening process.

Effect of Time and Temperature on Yield Stress




Effect of Time and Temperature on Yield Stress

Figure 4.22 The effect of again time and temperature on the yieldstress of 2014-T4 aluminum alloy. Note that, for eachtemperature, there is an optimal aging time for maximum strength.

Outline of Heat Treatment Processes for Surface Hardening




Outline of Heat Treatment Processes for Surface Hardening, con’t.



Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.

ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Heat-treating Temperature Ranges for Plain-Carbon Steels





g p g

Figure 4.23 Heat-treating temperature ranges for plain-carbonsteels, as indicated on the iron-iron carbide phase diagram.

Hardness of Steel as a Function of Carbon Content





Figure 4.24 Hardness of steels in the quenched andnormalized conditions as a function of carbon content.

Mechanical Properties of Steel as a Function of Tempering Temperature





Figure 4.25 Mechanicalproperties of oil-quenched 4340 steel asa function of temperingtemperature.



CAST IRONS

Fe-C Phase Diagram



Stable

Metastable



CAST IRONS

Grey CI

Ductile CI

White CI

Malleable CI

Alloy CI

Good castability C > 2.4%

Malleabilize

Stress concentrationat flake tips avoided

White Cast Iron

All C as Fe 3C (Cementite)



All C as Fe 3C (Cementite)

Microstructure Pearlite + Ledeburite + Cementite

Grey Cast Iron

< 1.25% Inhibits graphitization

[2.4% (for good castability), 3.8 (for OK mechanical propeties)]



Fe-C- Si + (Mn, P, S) Invariant lines become invariant regions in phase diagram

Si (1.2, 3.5) C as Graphite flakes in microstructure (Ferrite matrix)

< 0.1% retards graphitization; size of Graphite flakes

g p

3 3 3L ( ) ( ) Ledeburite Pearlite

Fe C Fe C Fe C

Si decreases EutectivitySi promotes graphitization ~ effect as cooling rateSolidification over a range of temperatures permits the nucleation and growth of GraphiteflakesChange in interfacial energy between /L & Graphite/L brought about by SiGrowth of Graphite along ‘a’ axis

Si eutectoid C

volume during solidification better castability

Ductile/Spheroidal Cast Iron

Graphite nodules instead of flakes (in 2D section)



Graphite nodules instead of flakes (in 2D section)

Mg, Ce, Ca (or other spheroidizing) elements are added

The elements added to promote spheroidization react with the solute inthe liquid to form heterogenous nucleation sites

The alloying elements are injected into mould before pouring (George- Fischer container)

It is thought that by the modification of the interfacial energy the ‘c’ and‘a’ growth direction are made comparable leading to spheroidal graphitemorphology

The graphite phase usually nucleates in the liquid pocket created by the

proeutectic

Ductile Iron/Nodular Iron



With Pearlitic matrix

10 mWith Ferritic Matrix With (Ferrite + Pearlite) Matrix

Ferrite Graphite nodules

Ductile Iron/Nodular Iron



Bull’s Eye

Ferrite

5 m

Pearlite (grey)

Graphite (black) Ferrite (White)

Malleable Cast Iron



MalleabilizeTo Increase DuctilityWhite Cast Iron Malleable Cast Iron

483 2 stage heat treatmentFe C (WCI) Graphite Temper Nodules (Malleable Iron)hrs

Stage I • (940-960) C (Above eutectoid temperature)• Competed when all Cementite Graphite



B: Graphite nucleation at /Cementite interface(rate of nucleation increased by C, Si)(Si solubility of C in driving force

for growth of Graphite)

A: Low T structure (Ferrite + Pearlite + Martensite) ( + Cementite)

C: Cementite dissolves C joining growing Graphite plates

Spacing between Cementite and Graphite spacing time (obtained by faster cooling of liquid)

Si t

Time for Graphitization

in Stage I

Addition of Alloying elements which increase the nucleation rate of Graphite temper nodules

Stage II • (720-730) C (Below eutectoid temperature)• After complete graphitization in Stage I Further Graphitization



Slow cool to the lower temperature such that does not form Cementite

C diffuses through to Graphite temper nodules(called Ferritizing Anneal )

Full Anneal in Ferrite + Graphite two phase region

Partial Anneal (Insufficient time in Stage II Graphitization) Ferrite is partial and the remaining transforms to Pearlite

Pearlite + Ferrite + Graphite

If quench after Stage I Martensite (+ Retained Austenite(RA))(Graphite temper nodules are present in a matrix of Martensite and RA)

Malleable Iron

l



Ferritic Matrix

Pearlitic Matrix

Fully Malleabilized Iron

Complete Ferritizing Anneal

10 m

Partially Malleabilized IronIncomplete Ferritizing Anneal

Pearlite (grey)

Graphite (black)

Ferrite (White)

Ferrite (White)

Graphite (black)

Growth of Graphite



Growth of Graphite Hunter and Chadwick

Double and Hellawell

Hillert and Lidblom

Growth of Graphite from Screw dislocations

Alloy Cast Irons

Cr Mn Si Ni Al



Cr, Mn, Si, Ni, Al

the range of microstructures

Beneficial effect on many properties high temperature oxidation resistance corrosion resistance in acidic environments wear/abaration resistance

Alloy Cast Irons

Graphite bearing

Graphite free

Cr addition (12- 35 wt %)

Excellent resistance to oxidation at high temperatures



High Cr Cast Irons are of 3 types:

12-28 % Cr matrix of Martensite + dispersed carbide29-34 % Cr matrix of Ferrite + dispersion of alloy carbides[(Cr,Fe) 23C6, (Cr,Fe) 7C3]

15-30 % Cr + 10-15 % Ni stable + carbides [(Cr,Fe) 23C6, (Cr,Fe) 7C3] Ni stabilizes Austenite structure

High Cr

29.3% Cr, 2.95% C

Ni:Stabilizes Austenitic structure



Graphitization (suppresses the formation of carbides)(Cr counteracts this tendency of Ni for graphitization)

Carbon content in EutecticMoves nose of TTT diagram to higher times easy formation of MartensiteCarbide formation in presence of Cr increases the hardness of the eutectic

structure Ni Hard Cast Irons (4%Ni, 2-8% Cr, 2.8% C )

Ni-Hard

4%Ni, 2-8% Cr, 2.8% C

Needles of Martensite

Transformation sequenceCrystallization of primary Eutectic liquid + alloy carbide

Martensite

Good abrasion resistance

Ni Resist Iron : 15-30% Ni + small amount of Cr :Austenitic Dendrites + Graphite plates/flakes + interdendritic carbides



Austenitic Dendrites Graphite plates/flakes interdendritic carbidesdue to presence of Cr

Resistant to oxidation (used in chemical processing plants, sea water, oilhandling operations…)

Ni-resist

Dendrites of Graphite plates

Silal Iron (trade name) : Alloy CI with 5% SiSi allows solidification to occur over larger temperature range



Si allows solidification to occur over larger temperature range promotes graphitization

Forms surface film of iron silicate resistant to acid corrosion

CI with 5 % Si

Fe-Ni Phase Diagram



Alloy Cast Irons



Bull’s

Eye

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