Variation of the uniaxial tensile behavior of ultrafine-grained pure aluminum after cyclic pre-deformation

摘要

To explore the influence of cyclic pre-deformation on the mechanical behavior of ultrafine-grained(UFG)materials with a high stacking fault energy(SFE),UFG Al processed by equal-channel angular pressing(ECAP)was selected as a target material and its tensile behavior at different pre-cyclic levels D(D=N_i/N_f,where N_i and N_f are the applied cycles and fatigue life at a constant stress amplitude of 50 MPa,respectively)along with the corresponding microstructures and deformation features were systematically studied.The cyclic pre-deformation treatment on the ECAPed UFG Al led to a decrease in flow stress,and a stress quasi-plateau stage was observed after yielding for all of the different-state UFG Al samples.The yield strengths_(YS),ultimate tensile strengths_(UTS),and uniform straineexhibited a strong dependence on D when D≤20%;however,when D was in the range from 20%to 50%,no obvious change in mechanical properties was observed.The micro-mechanism for the effect of cyclic pre-deformation on the tensile properties of the ECAPed UFG Al was revealed and compared with that of ECAPed UFG Cu through the observations of deformation features and microstructures.