Читать книгу Engineering Physics of High-Temperature Materials - Nirmal K. Sinha - Страница 54

There are a variety of planar defects that can occur within crystals. Many of these are due to dislocation and the slip of atomic planes. A common imperfection is a result of stacking faults – a deviation of the stacking sequence of layers in a crystal, often due to a missing or added layer. Stacking faults occur in a number of crystal structures, but the common example is that in close‐packed structures. For example, the ABCABCABC sequence of an FCC crystal could be disrupted by a missing C‐layer giving an ABCABABCABC structure.

Another type of planar defect is the twin boundary. This defect introduces a plane of mirror symmetry. For example, in the FCC structure, stacking sequence of a twin boundary would be ABCAB‐C‐BACBA.

A third type of planar defect is called the antiphase boundary. This defect occurs in ordered alloys where the crystallographic direction remains the same, but each side of the boundary has an opposite phase. For example, for the HCP crystal ABABABAB, an antiphase boundary takes the form of ABABBABA.