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MATSE 259

MATSE 259. Lecture 3: Phase Diagrams and Deformation of Materials Christopher L. Muhlstein, Ph.D. Department of Materials Science and Engineering The Pennsylvania State University University Park, PA. Last Lecture. Aluminum alloy designations Microstructures.

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MATSE 259

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  1. MATSE 259 Lecture 3: Phase Diagrams and Deformation of Materials Christopher L. Muhlstein, Ph.D. Department of Materials Science and Engineering The Pennsylvania State University University Park, PA

  2. Last Lecture • Aluminum alloy designations • Microstructures

  3. Lecture 3: Key Concepts and References • Reading binary phase diagrams • Introduction to age hardening • Elastic deformation of materials • Reference: Callister, Chapter 9

  4. Gibbs Phase Rule • Relationship between components, phases, state variables, and degrees of freedom • Gibbs phase rule P-T diagram for water Schaffer et al., The Science and Design of Engineering Materials (1999)

  5. Phase Diagrams • Binary phase diagram • phases present • composition of phases • relative amount of phases • Solid solutions Callister, Materials Science and Engineering: An Introduction (2003)

  6. 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

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

  8. Precipitation Hardening • Two-stage heat treatment • Solution heat treatment and quench • Precipitation heat treatment in a + b phase field (“aging”) Schematic of precipitation hardening heat treatment. Callister, Materials Science and Engineering: An Introduction (2003)

  9. Precipitation Hardening Peak Aged Underaged Overaged Aging behavior of a hypothetical aluminum alloy. Callister, Materials Science and Engineering: An Introduction (2003)

  10. Heat Treatment of Aluminum Alloys • Under, peak, and overaged aluminum alloys Precipitation hardened 7150-T651 alloy. Callister, Materials Science and Engineering: An Introduction (2003)

  11. Linear Elastic Behavior of Materials • Engineering stress, s, and strain, e • Hooke’s law • Poisson’s Ratio, n • Stiffness and compliance Schematic of tensile, shear, and torsion in elastic solids. Callister, Materials Science and Engineering: An Introduction (2003)

  12. Specimen geometry Experimental setup ASTM Standards E8 and E9 Measuring Tensile Behavior Schematic of tensile specimen. Schematic of tensile test. Callister, Materials Science and Engineering: An Introduction (2003)

  13. Room Temperature Elastic Moduli of Materials • Compare • Polymers • Metals • Ceramics A material property chart of Young’s modulus and density. Ashby, Materials Selection in Mechanical Design (1999)

  14. Room temperature behavior Elevated temperature behavior Elastic Behavior of Al, Fe, and Ti Alloys Room temperature elastic properties. Temperature dependence of elastic modulus of metals. Callister, Materials Science and Engineering: An Introduction (2003)

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