Effect of the route and strain of equal-channel angular pressing on structure and properties of oxygen-free copper

Structure and properties of oxygen-free copper (99.98%) in dependence on strain and routes during equal-channel angular (ECA) pressing at room temperature up to strains ɛ ∼ 29 are studied. At ɛ ∼ 29, according to orientation imaging microscopy (OIM) analysis, the minimum size of structure elements, 230 nm, corresponds to route Bc, and the maximum fraction of high-angle boundaries, 77%, corresponds to route A. The sizes of structure elements revealed by analysis were larger than those determined by transmission electron microscopy (TEM). The strength characteristics of oxygen-free copper after equal-channel angular pressing increase by a factor of 1.5–1.7 and remain virtually constant in the deformation range ɛ ∼ 6–29 for all routes. The maximum UTS and YS values correspond to route Bc. The ductility decreases after the first pass and increases after ten passes, especially for route Bc.