Improvement of high-cycle fatigue life in a 6061 Al alloy produced by equal channel angular pressing

In the present study, mechanical properties and fatigue behavior of solid solution treated 6061 Al alloy fabricated by equal channel angular pressing (ECAP) process were evaluated. Yield stress and ultimate tensile stress significantly increased after ECAP. A remarkably large enhancement in fatigue life, by a factor of about 10, compared to a T6 treated commercial 6061 Al alloy was recognized to occur in low and high cycle regimes after a single pass. Further deformation by ECAP, however, virtually eliminated this improvement especially in the high cycle regime. Fine-grained microstructure with low-grain boundary misorientation angles was proposed to yield the best result in fatigue performance in a 6061 Al alloy. The current result suggests that one may pay attention to a single passed material rather than multi-passed material if improvement in fatigue life is a primary concern for successful engineering applications.