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General Chemistry Principles, Patterns, and Applications, 2011

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<strong>and</strong> a plane defect involves an entire plane of lattice points in a crystal. A vacancy occurs where an atom is<br />

missing from the normal crystalline array; it constitutes a tiny void in the middle of a solid (). We focus<br />

primarily on point <strong>and</strong> plane defects in our discussion because they are encountered most frequently.<br />

Figure 12.15 Common Defects in Crystals<br />

In this two-dimensional representation of a crystal<br />

lattice containing substitutional <strong>and</strong> interstitial impurities, vacancies, <strong>and</strong> line defects, a dashed<br />

line <strong>and</strong> arrows indicate the position of the line defect.<br />

Impurities<br />

Impurities can be classified as interstitial or substitutional. An interstitial impurityis usually a smaller<br />

atom (typically about 45% smaller than the host) that can fit into the octahedral or tetrahedral holes in the<br />

metal lattice (). Steels consist of iron with carbon atoms added as interstitial impurities (). The inclusion<br />

of one or more transition metals or semimetals can improve the corrosion resistance of steel.<br />

Table 12.3 Compositions, Properties, <strong>and</strong> Uses of Some Types of Steel<br />

Name of<br />

Steel Typical Composition* Properties <strong>Applications</strong><br />

low-carbon

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