intro material sci-

7/31/2019 Intro Material Sci-

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Objectives

Introduce the field of materials science andengineering (MSE)Provide introduction to the classification of materials


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What is Materials Science andEngineering?

Materials Science and EngineeringComposition means the chemical make-up of a material.

Structure means a description of the arrangements of atoms orions in a material.Synthesis is the process by which materials are made fromnaturally occurring or other chemicals.Processing means different ways for shaping materials into

useful components or changing their properties.


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2003 Brooks/Cole Publishing / Thomson Learning


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Application of the tetrahedron of materials science and engineering to ceramicsuperconductors. Note that the microstructure-synthesis and processing-composition are all interconnected and affect the performance-to-cost ratio


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ex: hardness vs structure of steel

Properties depend on structure

Data obtained from Figs. 10.21(a)and 10.23 with 4wt%C composition,and from Fig. 11.13 and associateddiscussion, Callister 6e .Micrographs adapted from (a) Fig.10.10; (b) Fig. 9.27;(c) Fig. 10.24;and (d) Fig. 10.12, Callister 6e .

ex: structure vs cooling rate of steel Processing can change structure

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Structure, Processing, & Properties

Cooling Rate (C/s)

100

200

300

400

500

600

0.01 0.1 1 10 100 1000

(a)

30 m

(b)

30 m

(d)

30 m(c)

4 m

H a r d n e s s

( B H N )


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1. Pick Application Determine required Properties

2. Properties Identify candidate Material(s)

3. Material Identify required Processing

Processing: changes structure and overall shape ex: casting, sintering, vapor deposition, doping

forming, joining, annealing.

Properties: mechanical, electrical, thermal,magnetic, optical, deteriorative.

Material: structure, composition.

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The Materials Selection Process


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Electrical Resistivity of Copper:

Adding impurity atoms to Cu increases resistivity .

Deforming Cu increases resistivity .

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Adapted from Fig. 18.8, Callister 6e.(Fig. 18.8 adapted from: J.O. Linde,Ann Physik 5 , 219 (1932); andC.A. Wert and R.M. Thomson,Physics of Solids , 2nd edition,McGraw-Hill Company, New York,1970.)


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Space Shuttle Tiles: --Silica fiber insulation

offers low heat conduction .

Thermal Conductivity of Copper:--It decreases when

you add zinc!

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Fig. 19.0, Callister 6e.(Courtesy of LockheedMissiles and SpaceCompany, Inc.)

Adapted fromFig. 19.4W, Callister 6e. (Courtesy of Lockheed AerospaceCeramics Systems,Sunnyvale, CA)(Note: "W" denotes fig.is on CD-ROM.)

Adapted from Fig. 19.4, Callister 6e.(Fig. 19.4 is adapted from Metals Handbook: Properties and Selection: Nonferrous alloys and Pure Metals , Vol. 2, 9th ed., H. Baker,(Managing Editor), American Society for Metals,1979, p. 315.)


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Magnetic Permeability vs. Composition:--Adding 3 atomic % Si

makes Fe a better recording medium!

Adapted from C.R. Barrett, W.D. Nix, and A.S. Tetelman, The Principles of Engineering Materials , Fig. 1-7(a), p. 9,1973. Electronically reproducedby permission of Pearson Education, Inc.,Upper Saddle River, New Jersey.

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Fig. 20.18, Callister 6e.(Fig. 20.18 is from J.U. Lemke, MRS Bulletin ,Vol. XV, No. 3, p. 31, 1990.)

Magnetic Storage :--Recording medium

is magnetized byrecording head.


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Transmittance :

--Aluminum oxide may be transparent, translucent, or opaque depending on the material structure.

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Adapted from Fig. 1.2,Callister 6e.(Specimen preparation,P.A. Lessing; photo by J.Telford.)

single crystalpolycrystal:low porosity

polycrystal:high porosity


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Stress & Saltwater...

--causes cracks!

Heat treatment: slows

crack speed in salt water!

4 m--material:

7150-T651 Al "alloy"(Zn,Cu,Mg,Zr)

Adapted from Fig. 11.20(b), R.W. Hertzberg, "Deformation andFracture Mechanics of Engineering Materials" (4th ed.), p. 505, JohnWiley and Sons, 1996. (Original source: Markus O. Speidel, BrownBoveri Co.)

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Adapted from Fig. 17.0, Callister 6e.(Fig. 17.0 is from Marine Corrosion, Causes,and Prevention , John Wiley and Sons, Inc.,

1975.)

Adapted from Fig. 11.24,Callister 6e. (Fig. 11.24 provided courtesy of G.H.

Narayanan and A.G. Miller, Boeing Commercial Airplane Company.)


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Classification of Materials

Metals and AlloysCeramics, Glasses,and Glass-ceramicsPolymers (plastics), Thermoplastics and Thermosets

SemiconductorsComposite Materials


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Representative examples, applications, andproperties for each category of materials

Example of Applications Properties

Metals and AlloysGray cast iron Automobile engine blocks Castable, machinable,

vibration dampingCeramics andGlassesSiO2-Na2O-CaO Window glass Optically transparent,

thermally insulatingPolymersPolyethylene Food packaging Easily formed into thin,

flexible, airtight film


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Example of Applications Properties

SemiconductorsSilicon Transistors and integrated Unique electrical

circuits behavior

Composites Carbide cutting tools for High hardness, yetTungsten carbide machining good shock resistance-cobalt (WC-Co)

Table Continued


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Representative strengths of various categories of materials


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A section through a jet engine. Theforward compression section operates atlow to medium temperatures, and

titanium parts are often used. The rearcombustion section operates at hightemperatures and nickel-basedsuperalloys are required. The outsideshell experiences low temperatures, andaluminum and composites are

satisfactory. (Courtesy of GE AircraftEngines.)

A variety of complex ceramic components,including impellers and blades, which allowturbine engines to operate more efficientlyat higher temperatures. (Courtesy of Certech, Inc.)


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Polymerization occurs when small molecules, represented by the circles, combine to

produce larger molecules, or polymers. The polymer molecules can have a structurethat consists of many chains that are entangled but not connected (thermoplastics) orcan form three-dimensional networks in which chains are cross-linked (thermosets)


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Polymers are used in avariety of electronicdevices, includingthese computer dipswitches, wheremoisture resistanceand low conductivityare required. (Courtesyof CTS Corporation.)

Integrated circuits forcomputers and otherelectronic devices rely onthe unique electricalbehavior of semiconducting materials.(Courtesy of RogersCorporation.)

The X-wing for advancedhelicopters relies on amaterial composed of acarbon-fiber-reinforcedpolymer. (Courtesy of Sikorsky AircraftDivision UnitedTechnologiesCorporation.)


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Functional Classification of Materials

Aerospace BiomedicalElectronic Materials

Energy Technology and Environmental TechnologyMagnetic Materials Photonic or Optical MaterialsSmart Materials Structural Materials


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Functionalclassification of materials. Noticethat metals, plastics,and ceramics occur indifferent categories.A limited number of examples in eachcategory is provided


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Classification of Materials-Based on Structure

Crystalline material is a material comprised of one or manycrystals. In each crystal, atoms or ions show a long-range periodicarrangement.

Single crystal is a crystalline material that is made of only onecrystal (there are no grain boundaries).Grains are the crystals in a polycrystalline material. Polycrystalline material is a material comprised of many crystals

(as opposed to a single-crystal material that has only one crystal).Grain boundaries are regions between grains of a polycrystalline

material.


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Environmental and Other Effects

Effects of following factors must be accounted for in design toensure that components do not fail unexpectedly:

Temperature CorrosionFatigue Strain Rate


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Increasing temperaturenormally reduces thestrength of a material.Polymers are suitable onlyat low temperatures.Some composites, specialalloys, and ceramics, haveexcellent properties athigh temperatures


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Skin operating temperatures for aircraft have increased with the developmentof improved materials. (After M. Steinberg, Scientific American, October, 1986.)


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Schematic of a X-33 plane prototype. Notice the use of different materials fordifferent parts. This type of vehicle will test several components for theVenturestar (From A Simpler Ride into Space, by T.K. Mattingly, October,1997, Scientific American, p. 125. Copyright 1997 Slim Films.)


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Materials Design and Selection

Density is mass per unit volume of a material, usually expressed inunits of g/cm 3 or lb/in. 3

Strength-to-weight ratio is the strength of a material divided byits density; materials with a high strength-to-weight ratio are strongbut lightweight.


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