INFLUNECE OF STACKING FAULT ENERGY ON THE MICROSTRUCTURES, TENSILE AND FATIGUE PROPERTIES OF NANOSTRUCTURED Cu-Al ALLOYS

Influences of stacking fault energy (SFE) on the microstructures, tensile properties and fatigue behaviors of nanostructured (NS) Cu- Al alloys prepared by severe plastic deformation (SPD) were systematically summerized. With the reduction of SFE, it is found that the dominant formation mechanism of nanostructures gradually transformed from the dislocation subdivision to the twin fragmentation and the grain sizes also decrease; while microstructural homogeneity is achieved more readily in the materials with either high or low SFE than in the materials with medium SFE. The strength of NS Cu-Al significantly increases with decreasing the SFE, while there is an optimal SFE for the ductility of these materials. More significantly, the strength-ductility synergy of CuAl alloys is prominently enhanced with reducing the SFE. Finally, simultaneous improvements of low-cycle fatigue and high-cycle fatigue properties of NS Cu-Al alloys were achieved with decreasing the SFE. This can be attributed to the enhanced microstructure stability and the reduced strain localization in shear bands. With the reduction of SFE, the fatigue damage micro-mechanism was also transformed from grain boundary (GB) migration to other GB activities such as, atom shuffling, GB sliding and GB rotation.