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The high temperature of annealing may result in oxidation of the metal's surface, resulting in scale. If scale must be avoided, annealing is carried out in a special atmosphere, such as with endothermic gas (a mixture of carbon monoxide, hydrogen gas, and nitrogen gas). Annealing is also done in forming gas, a mixture of hydrogen and nitrogen.
Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity. In ferrous alloys, annealing is usually accomplished by heating the metal beyond the upper critical temperature and then cooling very slowly, resulting in the formation of pearlite. In both pure ...
The recrystallization temperature is temperature at which recrystallization can occur for a given material and processing conditions. This is not a set temperature and is dependent upon factors including the following: [3] Increasing annealing time decreases recrystallization temperature
The phase diagram shows, in pressure–temperature space, the lines of equilibrium or phase boundaries between the three phases of solid, liquid, and gas. The curves on the phase diagram show the points where the free energy (and other derived properties) becomes non-analytic: their derivatives with respect to the coordinates (temperature and ...
Precipitation strengthening is possible if the line of solid solubility slopes strongly toward the center of a phase diagram.While a large volume of precipitate particles is desirable, a small enough amount of the alloying element should be added so that it remains easily soluble at some reasonable annealing temperature.
Similarly, by annealing (and thus allowing for slow structural relaxation) the glass structure in time approaches an equilibrium density corresponding to the supercooled liquid at this same temperature. T g is located at the intersection between the cooling curve (volume versus temperature) for the glassy state and the supercooled liquid.
Quenching: Rapid cooling (quenching) after solution annealing freezes the high-temperature solid solution, preventing the precipitation of strengthening phases. Aging (Precipitation Hardening): During aging, the supersaturated solid solution becomes unstable. Fine precipitates, such as CuAl2 and Mg2Si, form within the aluminum matrix.
Stress relief and annealing are the processes that can be employed for this class of titanium alloys. The heat treatment cycles for beta alloys differ significantly from those for the alpha and alpha-beta alloys. Beta alloys can not only be stress relieved or annealed, but also can be solution treated and aged.