Fatigue life improvement of TC11 titanium alloy by novel electroshock treatment

Abstract

To improve the service life of titanium alloys, a novel electroshock treatment (EST) with low frequency, alternating pulse, and limited energy density is proposed in this study. The effects of different parameters process on the fatigue life of TC11 alloy were investigated. Experimental data show that low-cycle fatigue life of the alloys increased 22.5% by the appropriate EST. The mechanism affecting the fatigue life was studied by SEM and TEM. The results show that after the appropriate EST, the volume fraction of the α phase increased, the lath-like transformed β phase was broken and dissolved locally, accompanied by the formation of a secondary α phase and its morphological transformation from flake-like to more finely dispersed acicular. It was found that the appropriate EST led to the nanoscale solid-state phase transition; namely, the dissolution of an unstable brittle AlTiHx phase in the alloy matrix and precipitation of the Al24Ti8 strengthening phase with a size close to 5 nm in the β phase. These transitions occurred when the local maximum temperature of the sample recorded was only 296.8 °C. In summary, the microstructural evolution and nanoscale phase transformation of titanium alloy by the EST process significantly increased the fatigue life.