Microstructural evolution and mechanical properties of low SFE Cu-Al alloys processed by cryorolling followed by short-annealing

摘要

Cu-2% Al and Cu-4.5% Al alloys were developed by metal mould casting followed by homogenization at 800 degrees C for cryorolling. The homogenized samples were cryorolled (CR) up to the maximum possible reduction in area (similar to 75%). Activation energy for recrystallization of the CR samples was estimated by isoconversion methods using differential scanning calorimetry data; whereas, stored strain energy was determined by X-ray diffraction analysis. The activation energy for recrystallization correlated well with the stored energy of the corresponding sample. Microstructural evolution was analyzed by optical and transmission electron microscopy. The CR + annealed (225 degrees C) sample showed an improved yield strength (YS) of 810 MPa with a reasonable ductility of 5.1% The YS found to be 10 times higher than that of the cast + homogenized sample (76 MPa). This is attributed to the recovery of low angle grain boundaries, increasing grain boundary spacing, formation of nanotwins and decrease in the dislocation density without any recrystallization. The YS obtained by analytical modeling of the active strengthening mechanisms is highly corroborated with the experimental YS of the annealed sample. The Hall-Petch strengthening and dislocation strengthening found to play the pivotal role in the improvement of mechanical properties. (C) 2016 Elsevier Ltd. All rights reserved.