Recrystallization of Cu alloys

Copper based solid solutions with different contents of solute elements (Zn, Al, Ga, Sn, Ge) were deformed at room-temperature and at liquid Nitrogen temperature. The recrystallisation behaviour of these alloys has been investigated by means of dynamic and isothermal measurements of the resistivity (ρ). Variations of dρ/dT from ρ_0,α are interpreted in terms of changes in defect densities by recovery and recrystallisation. Deviations from a linear temperature dependence of the resistivity increase with increasing solute concentration. This deviation (i.e. Δρ^rec as determined at room temperature) also depends on the stacking fault energy γ. We observe a 1/γ²-dependency of Δρ^rec which is also influenced by the deformation temperature. During deformation, γ controls the possibility to store deformation energy in the form of dislocations and deformation twins. In combination with the general trend of alloying elements to shift recrystallisation to higher temperatures, the recrystallisation behaviour of single-phase copper alloys has been described qualitatively.

The results are published by J. Freudenberger, et al.: "Studies on recrystallization of single-phase copper alloys by resistance measurements" in Acta Materialia 58 (2010), pp. 2324-2329 (DOI). A detailled investigation of the resulting mechanical properties are discussed by V. Subramanya Sarma, et al.: "Role of stacking fault energy in strengthening due to cryo-deformation of FCC metals" in Materials Science and Engineering A (2010), in press (DOI).

Equipment for resistance and resistivity measurements at elevated and high temperatures available at the IFW Dresden (left). Change of resistivity of deformed Copper alloys during recrystallization as a function of their stacking fault energy (right).