Enhanced strength and fatigue life of ultra-fine grain Fe–36Ni Invar alloy

The mechanical behavior and fatigue life of ultra-fine grain (UFG) Fe–36%Ni Invar alloy fabricated by severe plastic deformation (SPD) is investigated in both high-cyclic and low-cyclic regimes. A significant enhancement of mechanical properties has been achieved via equal-channel angular pressing (ECAP); the yield stress and the fatigue limit are increased by a factor of three and two, respectively, when compared with those of ordinary Invar alloy with conventional grain size. The fatigue characteristics are determined and tabulated in terms of cyclic stress–strain curves (CSSC), endurance limit, Coffin–Manson and Basquin parameters. It has been shown that the notable improvement of both low-cyclic and high cyclic properties is possible after SPD depending on the processing route.