8 Examples of precipitation hardening materials.7 Computational discovery of new alloys.Precipitation heat treating involves the addition of impurity particles to increase a material's strength. Solid solution strengthening involves formation of a single-phase solid solution via quenching. Two different heat treatments involving precipitates can alter the strength of a material: solution heat treating and precipitation heat treating. Solution treatment and aging is sometimes abbreviated "STA" in specifications and certificates for metals. Unlike ordinary tempering, alloys must be kept at elevated temperature for hours to allow precipitation to take place. Just as the formation of ice in air can produce clouds, snow, or hail, depending upon the thermal history of a given portion of the atmosphere, precipitation in solids can produce many different sizes of particles, which have radically different properties.
The impurities play the same role as the particle substances in particle-reinforced composite materials. Since dislocations are often the dominant carriers of plasticity, this serves to harden the material.
Precipitation hardening relies on changes in solid solubility with temperature to produce fine particles of an impurity phase, which impede the movement of dislocations, or defects in a crystal's lattice. In superalloys, it is known to cause yield strength anomaly providing excellent high-temperature strength. Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and some steels and stainless steels.
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