MICROSTRUCTURE STABILITY AND CREEP BEHAVIOUR OF ALLOYS PROCESSED BY ECAP

Coarse-grained binary Cu and Al alloys were processed by equal-channel angular pressing (ECAP) in order to evaluate the effect of severe plastic deformation on the thermal stability of resulting ultrafine-grained microstructure after ECAP followed by creep loading of the pressed alloys. ECAP was conducted at room temperature with a die that had an internal angle of 90 degrees between the two parts of the channel. The subsequent extrusion passes were performed by route Bc. Microstructure of samples up to 12 ECAP passes was characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with the electron backscatter diffraction (EBSD) unit. Constant load creep tests in tension were performed at 0.3 - 0.5 Tm and at different applied stresses. It was found that the creep behaviour is influenced by high-angle grain boundaries created by ECAP and creep fracture occurred along the shear bands which are situated near shear plane of the last ECAP pass.