matse 259 spring 2007, c. muhlstein© c. muhlstein, 2007 the contents of this lecture are protected...

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MATSE 259 Spring 2007, C. Muhlstein© C. Muhlstein, 2007

The contents of this lecture are protected under U.S. copyright law and should not be duplicated or redistributed for commercial purposes.

MATSE 259

Lecture 3: Phase Diagrams and Deformation of Materials

Christopher L. Muhlstein, Ph.D.

Department of Materials Science and EngineeringThe Pennsylvania State University

University Park, PA

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Last Lecture

• Aluminum alloy designations

• Microstructures

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Lecture 3: Key Concepts and References

• Reading binary phase diagrams• Introduction to age hardening• Elastic deformation of materials

• Reference: Callister, Chapter 9

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Gibbs Phase Rule

• Relationship between components, phases, state variables, and degrees of freedom

• Gibbs phase rule

P-T diagram for water2 PCFSchaffer et al., The Science and Design of Engineering Materials (1999)

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Phase Diagrams

• Binary phase diagram– phases present– composition of

phases– relative amount of

phases• Solid solutions

Callister, Materials Science and Engineering: An Introduction (2003)

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Dispersion Strengthening and Precipitation Hardening

• Mechanism: small particles in a metal can impede deformation

• Dispersion strengthening– Particulates added to the (usually liquid) material– Material added should not react with base metal– Composite

• Precipitation Hardening– “Age hardening”– Particulates created in material by heat treatment– Nucleation and growth process– Phase diagram used to identify amenable alloy systems

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Precipitation Hardening

• Phase diagram features– “Appreciable” solid

solubility of one component

– Solubility limit that decreases rapidly

– Alloy composition less than solubility limit

– Necessary, but not sufficient, condition for precipitation-hardenable alloy

Hypothetical phase diagram of precipitation-hardenable alloy.


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• Two-stage heat treatment– Solution heat

treatment and quench

– Precipitation heat treatment in + phase field (“aging”)


Schematic of precipitation hardening heat treatment.

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Underaged

Peak Aged

Overaged

Aging behavior of a hypothetical aluminum alloy.


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Heat Treatment of Aluminum Alloys

• Under, peak, and overaged aluminum alloys

Precipitation hardened 7150-T651 alloy.Callister, Materials Science and Engineering: An Introduction (2003)

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Linear Elastic Behavior of Materials

• Engineering stress, , and strain,

• Hooke’s law• Poisson’s Ratio, • Stiffness and

compliance

Schematic of tensile, shear, and torsion in elastic solids.


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Measuring Tensile Behavior

Schematic of tensile test.Schematic of tensile specimen.

• Specimen geometry• Experimental setup• ASTM Standards E8

and E9


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Room Temperature Elastic Moduli of Materials

• Compare– Polymers– Metals– Ceramics

Ashby, Materials Selection in Mechanical Design (1999)

A material property chart of Young’s modulus and density.

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Elastic Behavior of Al, Fe, and Ti Alloys

Alloy Young’s Modulus, E (GPa)

Poisson’s Ratio, v

Al 69 0.33

Ti 107 0.34

Steel 207 0.30

• Room temperature behavior

• Elevated temperature behavior

Temperature dependence of elastic modulus of metals.


Room temperature elastic properties.

matse 259 spring 2007, c. muhlstein© c. muhlstein, 2007 the contents of this lecture are protected...

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