On the elevated-temperature deformation behavior of polycrystalline Cu subjected to predeformation by multiple compression

Strain rate sensitivity of flow stress and creep resistance were studied during creep at elevated temperature of 373 K as function of prestrain in multiple uniaxial compression at room temperature for pure Cu99.99 with initial grain size d ≈ 50   μ m. Moderate prestrains ≤ 2 strengthen the material by formation of subgrains with low-angle boundaries, while severe prestrains enhance the strain rate sensitivity and soften the material in the saturation state of deformation. The results are discussed in terms of increase of the fraction of high-angle boundaries in the subgrain structure produced by severe prestraining influencing the balance of generation and annihilation of dislocations.