Microscopic Defects and Macroscopic Defects in Crystalline Materials

Classification of crystallographic defects (microscopic defects) is frequently made according to the geometry or dimensionality of the defect. Other macroscopic defects exist in all solid materials that are much larger than microscopic, these include pores, cracks, foreign inclusions, and other phases.

  • Microscopic Defects
    • Point Defects. Point defects have atomic dimensions, so that they occur only at or around a single lattice point. They are not extended in space in any dimension.
    • Line Defects. Line defects are generally many atoms in length. Line defects are called dislocations and occur in crystalline materials only. Dislocations are especially important in materials science, because they help determine the mechanical strength of materials.
    • Planar Defects. A planar defect is a discontinuity of the perfect crystal structure across a plane. Interfacial defects are boundaries that have two dimensions and normally separate regions of the materials that have different crystal structures and/or crystallographic orientations.
  • Macroscopic Defects
    • Three-dimensional macroscopic defects are called bulk defects. They generally occur on a much larger scale than the microscopic defects. These macroscopic defects generally are introduced into a material during refinement from its raw state or during fabrication processes. These include cracks, pores, foreign inclusions, and other phases. The working and forging of metals can cause cracks that act as stress concentrators and weaken the material. Any welding or joining defects may also be classified as bulk defects.
      • Three-dimensional macroscopic or bulk defects, such as pores, cracks, or inclusions.
      • Voids — small regions where there are no atoms, and which can be thought of as clusters of vacancies.
      • Impurities can cluster together to form small regions of a different phase. These are often called precipitates.
Materials Science:
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  2. U.S. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 2 and 2. January 1993.
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  8. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.

See above:

Crystallographic Defects