In this work we study the high pressure torsion (HPT) of a two-phase Cu–3.9 at. % Ag alloy in two different states: (i) as-cast consisting of a (Cu) solid solution with diluted 1.9 at.% Ag and another 2 at.% Ag as fine silver precipitates and (ii) an almost homogeneous solid solution with diluted 3.9 at.% Ag obtained by homogenization at T = 780 °C, 900 h and subsequent water quenching. HPT at room temperature causes the partial dissolution of precipitates in the as-cast samples and partial decomposition of the solid solution in homogenized samples. After HPT, the solute concentration in the matrix is the same in both samples (about 2.9–3.0 at.% Ag). Thus, it does not depend on the initial state and is higher than the equilibrium solubility limit at the HPT temperature. This concentration is equal to solubility limit at the effective temperature of Teff ≈ 680 °C.
We also proposed the model describing the dynamic equilibrium between dissolution and precipitation in HPT. Assuming that HPT fixes the composition at matrix-precipitate interfaces, we show that HPT-enhanced diffusive transport of species is the process likely controlling the observed steady-state composition in the matrix and precipitate average diameter.