Effect of SFE on tensile and fatigue behavior of ultrafine grained Cu-Zn and Cu-Al alloys developed by cryo-rolling/forging

An attempt has been made to investigate the high cycles fatigue behavior of the ultrafine grained (UFG) low SFE Cu-Zn and Cu-Al alloys processed through cryorolling/cryoforging followed by short-annealing. The samples (CRed Cu-9.6% Zn, CFed Cu-9.6% Zn & Cu-4.5% Al, and CRed+short-annealed (225 °C) Cu-4.5% Al), which showed better combinations of YS, ductility and fracture toughness, have been selected to investigate their fatigue characteristics. High cycle fatigue strength of the UFG alloys was found to be consistent in accordance with the static mechanical properties of the corresponding sample. For example, the CFed Cu-4.5% Al alloy samples showed superior fatigue strength along with the best combination of YS, ductility and fracture toughness as compared to that of the other samples. The improved fatigue strength of the alloys has been discussed in the light of effect of low SFE, complex and unique microstructural constituents developed by cryodeformation and role of static mechanical properties of the corresponding sample. TEM analysis after fatigue tests and fractography analysis near to fracture zones corroborated well in explaining the improvement of fatigue life of the UFG alloys.