New insights on the formation of supersaturated solid solutions in the Cu-Cr system deformed by high-pressure torsion

In the Cu-Cr system, the formation of supersaturated solid solutions can be obtained by severe plastic deformation. Energy-dispersive synchrotron diffraction measurements on as-deformed Cu-Cr samples as a function of the applied strain during deformation confirm the formation of supersaturated solid solutions in this usually immiscible system. Due to evaluation of the diffraction data by a newly developed energy-dispersive Rietveld program, lattice parameter and microstructural parameters such as domain size and microstrain are determined for as-deformed as well as annealed samples. The obtained information is used to deepen the understanding of the microstructural evolution and the formation of supersaturated solid solutions during severe plastic deformation. Complimentary transmission electron microscopy investigations are furthermore performed to characterize the evolving microstructure in detail. After annealing at elevated temperatures, the formed solid solutions decompose. Compared to the as-deformed state, an enhanced hardness combined with a high thermal stability is observed. Possible mechanisms for the enhanced hardness are discussed.