Lecture31 - ME 382 Lecture 31 CREEP MECHANISMS Diffusional...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
ME 382 Lecture 31 5/iv/06 1 C REEP M ECHANISMS Diffusional (linear) creep At low stresses creep occurs by diffusion provided T ! 0.4 T M Gibbs free energy is proportional to normal stresses on grain boundaries Driving force for diffusion is gradient across grains of normal stresses on boundaries Consider a case of pure shear Normal tensile stress on “B” > normal tensile stress on “A” Energy of atoms on grain boundary “B” < energy on grain boundary “A” Atoms diffuse from “A” “B” Creep is a shear driven process Requires a difference in normal stress on boundaries of different orientations No creep under hydrostatic stress (same stress at “A” and “B”) Two diffusion routes between grain boundaries (i) Lattice (bulk) diffusion creep Also known as “Nabarro-Herring” creep (1948/1950) Atoms move through the grain by bulk (lattice) diffusion Width of diffusion path = grain size
Background image of page 1

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

View Full DocumentRight Arrow Icon
ME 382 Lecture 31 5/iv/06 2 (ii) Grain-boundary creep Also known as “Coble” creep (1963) Atoms move along the grain boundaries Width of diffusion path = region of disorder of width
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/20/2011 for the course ME 382 taught by Professor Garikipati during the Spring '08 term at University of Michigan.

Page1 / 5

Lecture31 - ME 382 Lecture 31 CREEP MECHANISMS Diffusional...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online