Engineering Science 1021A/B Lecture Notes - Lecture 14: Grain Boundary
17 May 2018
School
Department
Professor
Surface defects: boundaries/planes that separate a material into regions
•
Grains and Grain Boundaries
Engineering materials are made up of grains
•
Grain boundaries separate regions (grains) in the material in which the lattice is
orientated differently in space
•
Grains have the same crystal structure but a different orientation
•
•
The Hall-Petch Relationship
Plastic deformation is the due process of slip/dislocations moving through the
material
•
It is more difficult for a dislocation to get past imperfections (point/surface
defects) in the crystal lattice
•
If we can increase the number of defects, we should be able to make the
material stronger
•
One method of doing this is to decrease the grain size
If the grain size decreases the amount of grain boundary surface increases
○
•
The Hall-Petch relationship describes the yield strength of a material as a
function of the grain size
§
𝑑: diameter of the grain
§
○
•
Measuring Grain Size
Mean intercept method: draw random line and count grain boundary
intersections
•
Surface Defects
Surface defects: boundaries/planes that separate a material into regions•
Grains and Grain Boundaries
Engineering materials are made up of grains•
Grain boundaries separate regions (grains) in the material in which the lattice is
orientated differently in space
•
Grains have the same crystal structure but a different orientation•
•
The Hall-Petch Relationship
Plastic deformation is the due process of slip/dislocations moving through the
material
•
It is more difficult for a dislocation to get past imperfections (point/surface
defects) in the crystal lattice
•
If we can increase the number of defects, we should be able to make the
material stronger
•
One method of doing this is to decrease the grain size
If the grain size decreases the amount of grain boundary surface increases
○
•
The Hall-Petch relationship describes the yield strength of a material as a
function of the grain size
§
𝑑: diameter of the grain
§
○
•
Measuring Grain Size
Mean intercept method: draw random line and count grain boundary
intersections
•
Surface Defects
