# lecture 9 - ME 330 Engineering Materials Lecture 9...

This preview shows pages 1–8. Sign up to view the full content.

Lecture 9 Solidification and Phase Diagrams Stephen D. Downing Mechanical Science and Engineering © 2001 - 2010 University of Illinois Board of Trustees, All Rights Reserved ME 330 Engineering Materials

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ME 330 - Lecture 9 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 1 of 31 This Lecture . .. ± Solidification ± Phase Diagram Definitions ± Eutectic Phase Diagram ± Liquidus/Solidus ± Solidification microstructures ± Invariant Points ± Intermediate compounds ± Ternary Phase Diagram
ME 330 - Lecture 9 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 2 of 31 Example Problem Consider a single crystal of silver oriented such that a tensile stress is applied along a [001] direction. If slip occurs on a (111) plane and in a [101] direction, and is initiated at an applied tensile stress of 1.1 MPa (160 psi), compute the critical resolved shear stress.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ME 330 - Lecture 9 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 3 of 31 Example Problem Two previously undeformed specimens of the same metal are to be plastically deformed by reducing their cross-sectional areas. One has a circular cross section, and the other is rectangular; during deformation the circular cross section is to remain circular, and the rectangular is to remain as such. Their original and deformed dimensions are as follows: 13.7x55.1 15.9 Deformed dimensions 20x50 18.0 Original dimensions Rectangular (mm) Circular (diameter,mm) Which of the specimens will be the hardest after plastic deformation, and why?
ME 330 - Lecture 9 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 4 of 31 Development of Microstructure ± Begin with molten metal ± Remove heat (lower temperature) ± Solid metal forms ± Nucleation ± Need to overcome energy barrier to initiate nucleation ± Usually large number of nucleation sites ± Growth ± Competitive - multiple nucleation sites fight for remaining liquid ± Certain growth directions are preferred

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
ME 330 - Lecture 9 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 5 of 31 Controlling Microstructure (Nucleation) ± Heterogeneous Nucleation ± “Grain refiners” promote nucleation ± Add solid second phase which act as nucleation sites ± Change alloy which changes melting temperature from pure metal ± Decrease the critical nucleation size more nucleation sites ± Mold walls also can act as nucleation sites ± Mold vibration ± Break off dendrites ± Broken dendrites act as nucleation sites ± Heat mold ± Suppress chill zone at wall ± Superheat molten metal
ME 330 - Lecture 9 © 2010 Stephen Downing, University of Illinois at Urbana-Champaign, All Rights Reserved 6 of 31 Terminology ± System : For our purposes, alloy under consideration ± Fe/C or Pb/Sn ± Component : Pure elements of which an alloy is composed ± Fe or C, Pb or Sn ± Solute : Component of solution being dissolved ± Solvent : Component of solution in greatest amount ± Solubility

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 10/03/2011 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

### Page1 / 33

lecture 9 - ME 330 Engineering Materials Lecture 9...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online