The effect of flow localization and shear bands development on the structure and mechanical behavior of Cu-4.98 wt.% Ti alloy

Hot compression tests were performed on solution treated (ST) Cu-Ti alloy deformed within a temperature range of 673 K - 1173 K at constant strain rate of 1.4 x 10-4 s-1 and 6.9 x 10-3 s-1. Shear banding, dynamic precipitation and dynamic coarsening have operated simultaneously with different effectiveness depending on the temperature and used strain rate. At low temperature, 673 K, intergranular cracks and flow localization were found to be responsible for the material fracture at εt∼0.1-0.2. At 873 K and above, a flow stress maximum was followed by monotonic flow softening range. Initial hardening range has resulted from both strain and precipitation hardening. Structural observations leads to the conclusion that an interaction of localized flow and discontinuous precipitation within shear bands was responsible for effective flow stress decrease at larger strains. At high deformation temperature, the flow softening of ST samples has resulted from cellular growth and combined effect of flow localization and discontinuous precipitation within sheared area. At high strain rates, the shear banding was found to proceed the precipitation and the initial flow softening has resulted from shear bands development rather than discontinuous precipitation. During deformation at 873 K - 1073 K and low strain rate, discontinuous precipitation was observed since the beginning of the tests and the localized flow was intensified due to particles dynamic coarsening within shear bands. The structural flow localization effects were limited for overaged (OA) and hot deformed samples. During deformation above the solvus temperature, dynamic recrystallization of the material was observed for both ST and OA samples. (orig.)