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Material Defects Overview

The document discusses different types of defects in solids: point defects like vacancies and interstitials, line defects like dislocations, and area defects like grain boundaries. Point defects can arise from vacancies in the crystal lattice or from impurity atoms. Line and area defects influence material properties, with grain boundaries controlling effects like crystal slip. Defects may be desirable or undesirable depending on the intended use of the material.

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Garion Charles
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18 views3 pages

Material Defects Overview

The document discusses different types of defects in solids: point defects like vacancies and interstitials, line defects like dislocations, and area defects like grain boundaries. Point defects can arise from vacancies in the crystal lattice or from impurity atoms. Line and area defects influence material properties, with grain boundaries controlling effects like crystal slip. Defects may be desirable or undesirable depending on the intended use of the material.

Uploaded by

Garion Charles
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Defects

Saturday, October 7, 2017 4:52 PM

TYPES OF IMPERFECTIONS

1. Point Defects

• Vacancy atoms
• Interstitial atoms
• Substitutional atoms

2. Line Defects

• Dislocations

3. Area Defects

• Grain Boundaries

4. Bulk Defects

Point Defects

Two Types of Self-interstitials

Two outcomes if impurity (B) added to host (A):

• Solid solution of B in A(i.e., random dist. Of point defects)

Substitutional alloy Interstitial alloy


(e.g., Cu in Ni) (e.g., C in Fe)

Notes Page 1
Substitutional alloy Interstitial alloy
(e.g., Cu in Ni) (e.g., C in Fe)

• Solid solution of B in A plus particles of a new phase (usually for a larger amount of B)

Second phase particle


--different composition
--often different structure.

Notes Page 2
AREA DEFECTS: GRAIN BOUNDARIES

Grain boundaries:
• are boundaries between crystals.
• are produced by the solidification process, for example.
• have a change in crystal orientation across them.
• impede dislocation motion.

 Examples:

SUMAMARY

• Point, Line, and defects arise in solids.


• The number and type of defects can be varied and controlled (e.g., T controls vacancy conc.)
• Defects affect material properties (e.g., grain boundaries control crystal slip)
• Defects may be desirable or undesirable (e.g., dislocations may be good or bad, depending on whether plastic deformation is desirable or
not.)

Notes Page 3

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