C Muhlstein 2007 MATSE 259 Spring 2007 C

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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 The contents of this lecture are protected under U. S. copyright law and should not be. PA duplicated or redistributed for commercial purposes. University Park, 1

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Last Lecture • Aluminum alloy designations • Microstructures 2

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Lecture 3: Key Concepts and References • Reading binary phase diagrams • Introduction to age hardening • Elastic deformation of materials • Reference: Callister, Chapter 9 3

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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) 4

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Phase Diagrams • Binary phase diagram – phases present – composition of phases – relative amount of phases • Solid solutions Callister, Materials Science and Engineering: An Introduction (2003) 5

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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 6

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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) 7

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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) 8

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Precipitation Hardening Peak Aged Underaged Overaged Aging behavior of a hypothetical aluminum alloy. Callister, Materials Science and Engineering: An Introduction (2003) 9

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Heat Treatment of Aluminum Alloys • Under, peak, and overaged aluminum alloys Precipitation hardened 7150 -T 651 alloy. Callister, Materials Science and Engineering: 10 An Introduction (2003)

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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: 11 An Introduction (2003)

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Measuring Tensile Behavior • Specimen geometry • Experimental setup • ASTM Standards E 8 and E 9 Schematic of tensile specimen. Schematic of tensile test. Callister, Materials Science and Engineering: 12 An Introduction (2003)

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein 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) 13

© C. Muhlstein, 2007 MATSE 259 Spring 2007, C. Muhlstein Elastic Behavior of Al, Fe, and Ti Alloys • Room temperature behavior • Elevated temperature behavior Room temperature elastic properties. Alloy Young’s Modulus, E (GPa) Poisson’s Ratio, v Al 69 0. 33 Ti 107 0. 34 Steel 207 0. 30 Temperature dependence of elastic modulus of metals. Callister, Materials Science and Engineering: 14 An Introduction (2003)