Ch 6 Flashcards
Mass transport by atomic motion
diffusion
in diffusion material move to what type of concentrations
high to low
atoms moving from high to low concentrations in an alloy
interdiffusions
Diffusion that occurs in pure metals
self-diffusion
Atoms in a solid material are in
constant motion
What conditions must be present for an atom to move
- ) there must be an empty adjacent site
2. ) atom must have sufficient (vibrational) energy to break bonds with its neighboring atooms
Diffusion increases with
Increasing temperature
2 models for metallic diffusion
Vacancy and Interstital Diffusion
atoms exchanging with vacancies
Vacancy diffusion
occurs when smaller atoms move between atoms
interstital diffusion
Is intersital diffusion more rapid than vacancy diffusion?
yes
Why is intersitital diffusion more rapid?
More small mobile atoms and more empty interstitial sites
For vacancy diffusion, what diffusions can occur?
Self-diffusion and interdiffusion
process of hardening the surface of a metal, often low carbon steel, by diffusing elements into the material surface, forming a thin layer of a harder alloy
Case Hardening
What diffusion is case hardening>
interstitial diffusion
