Solid solution strengthening

The mixed-crystal solidification changes the mechanical properties of solid materials by the incorporation or substitution of the interstitial atoms.

Solid with a long-range order have a regular crystal structure. If foreign atoms incorporated into the crystal structure, it will be ( the crystal lattice ) distorted. If the distortion of individual atoms or molecules, so we speak of a point defect. Atoms with similar atomic radius take a substitutional site in the crystal lattice, significantly smaller atoms ( in metals, in practice, H, O, B, C, N) an interstitial site. The distortion of the crystal lattice Disabled sliding motions in the crystal. Sliding movements can no longer run in a plane but have to move to the distortions around, resulting in a higher energy requires. The material has become so fixed.

Solid-solution strengthening in metals

The mixed-crystal solidification is used specifically in metals, to harden them. Pure metals (eg Fe, Al, Cu, Ni, Mg) are a few exceptions, very soft. Only through a solidifying metals are as hard as we know it from everyday life. The solid solution strengthening is one of four elementary strength-enhancing methods and requires that solve other elements in the parent metal. There are metals with a complete solubility, which means that the two metals to form only one phase at each concentration, and metals having limited solubility, in which is formed a second phase when the solubility limit is exceeded. A mixed crystal having only a phase in two stages is referred to as a crystal mixture. However, a crystal mixture may comprise a solid solution strengthening. The higher the concentration of dissolved impurities, the higher is the solid solution strengthening. Just causes a greater deviation of the atomic radii greater consolidation. In general, smaller substitution atoms through the lattice distortion effect a higher hardening rate than larger substitution atoms. However, the more the atomic radii are different, the lower the solubility of the substitution atoms. The solubility is also also temperature dependent. In most cases, the solubility of impurities increases with the temperature. Therefore, the solid solution strengthening is a strength-enhancing method that is resistant against heat. In addition to the hardness increases by the solid solution strengthening of the tensile strength. Breaking elongation, electrical conductivity and the melting temperature decrease, as a rule.

• Crystallography