*3.6. Tensile Tests*

Tensile tests showed that the HPTE method resulted in an increase in the yield strength of Cu by more than twice that of the initial annealed state (370 MPa vs. 130 MPa) and a significant ultimate tensile strength enhancement of 430 MPa, with no changes in total elongation (Figure 8b, Table 2).

A rapid strengthening and a short uniform elongation range characterized the stress–elongation curve of copper after HPTE. A decrease of uniform elongation from ~16% in the annealed state to ~2% after the HPTE deformation was a typical behavior for the materials produced by SPD methods. However, after the deformation was localized, the elongation to fracture reached 30%, which was two times higher than post-necking elongation of the annealed copper (Figure 8b).
