substitutionalseoksissa

Substitutional solid solutions, often called substitutional alloys, are homogeneous crystalline phases in which solute atoms partially replace solvent atoms on lattice sites. In these alloys, the solute atoms occupy positions that would otherwise be held by solvent atoms, rather than sitting in interstitial spaces between the atoms of the lattice. The result is a single-phase material with a continuous range of compositions.

The formation and extent of substitutional solubility are governed by several factors known as the Hume-Rothery rules. Favorable substitution requires similar atomic sizes (typically within about 15%), the same crystal structure for the solute and solvent, comparable electronegativities, and similar valence. When these conditions are met, substantial amounts of solute can dissolve in the solvent to form a solid solution, often with a random distribution of solute atoms on lattice sites. Depending on the system and temperature, solubility can be complete across the composition range or limited, giving rise to two-phase regions or ordered intermetallic compounds at specific compositions.

Properties of substitutional alloys are strongly influenced by lattice distortion and chemical interactions. They commonly exhibit altered mechanical properties such as increased strength and hardness, sometimes at the expense of ductility, as well as changes in electrical and thermal conductivity and corrosion behavior. Some substitutional systems also undergo ordering at lower temperatures, leading to superlattice structures.

Classic examples include brass (copper with zinc substituting on copper sites) and copper-nickel systems, as well as aluminum-magnesium or iron-n nickel alloys. Substitutional alloys are foundational in metallurgy for tailoring material properties through composition and heat-treatment.