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Which one of the following is a line imperfection?

1. Which one of the following, is a line imperfection? Explanation: Dislocations look like lines in the lattice, which are one dimensional. So it falls under the category of line imperfections.

What are the types of line defect?

  • Point defects (vacancies, interstitial defects, substitution defects)
  • Line defect (screw dislocation, edge dislocation)
  • surface defects (material surface, grain boundaries)
  • Substitutional – one atom is replaced by as different type of atom.
  • Interstitial – extra atom is inserted into the lattice structure at a.

What is meant by line defect?

definition. In crystal defect. Line defects, or dislocations, are lines along which whole rows of atoms in a solid are arranged anomalously. The resulting irregularity in spacing is most severe along a line called the line of dislocation. Line defects can weaken or strengthen solids.

What is a surface defect?

Surface defects are the boundaries, or planes, that separate a material into regions, each region having the same crystal structure but different orientations.

What kind of defect is a grain boundary?

A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are 2D defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material.

Why do grain boundaries increase diffusion?

Due to the high concentration of defects in the grain contact area resulting from their crystallographic misalignment, diffusive transfer along the grain boundaries occurs much faster than in their bulk, where the defect concentration is much smaller (bulk diffusion), but slower than in the boundary between the solid …

What is high-angle grain boundaries?

Generally, it is assumed that low-angle grain boundaries (LAGBs) are those with a misorientation less than about 15 degrees. In contrast, the misorientation of high-angle grain boundaries (HAGBs) is greater than about 15 degrees.

What are twin boundaries?

Twin boundaries occur when two crystals of the same type intergrow so that only a slight misorientation exists between them. It is a highly symmetrical interface, often with one crystal the mirror image of the other; also, atoms are shared by the two crystals at regular intervals.

Why identical twins are always of the same gender?

Identical (monozygotic) twins are always of the same sex because they form from a single zygote (fertilized egg) that contains either male (XY) or female (XX) sex chromosomes. Fraternal twins can be either two girls, two boys, or one of each.

What are annealing twins?

Annealing twins are formed as a consequence of growth accidents during the recrystallisation of deformed cubic-close packed metals such as alpha-brass, copper, nickel and austenitic iron [Note 2]. Annealing twins should be distinguished from mechanical twins.

What is twinning plane for rhombohedral crystal?

For a centrosymmetrical crystal structure, both twin laws give rise to the same twin. ). Important examples are cubic twins with [111] as twofold twin axis or (111) as twin plane and rhombohedral twins with [001] as twin axes or (001) as twin plane (hexagonal description).

What does Twining mean?

1. To twist together (threads, for example); intertwine. 2. To form by twisting, intertwining, or interlacing: twined the cord from plant fibers. 3.