Effect of Volume Fraction of Gradient Nanograined Layer on Low-Cycle Fatigue Behavior of Cu

Abstract

Low-cycle fatigue properties and cyclic behaviors of two pure Cu samples skinned with different volume fractions of gradient nanograined (GNG) layer are investigated under total strain-amplitude-controlled fatigue tests. Increasing the volume fraction of high-strength GNG layer can greatly elevate the cyclic stress amplitude of GNG/coarse grain (CG) Cu, compared with that of CG Cu fatigued at the same strain amplitude. Distinctly, it does not clearly influence the low-cycle fatigue life of GNG/CG samples with different GNG volume fractions, i.e., both exhibit comparable fatigue lives, even longer than their CG counterpart. Such enhanced low-cycle fatigue life is mainly due to the progressive homogenization of the gradient surface nanostructure, which effectively suppresses the surface roughening and fatigue cracking of the GNG/CG samples during cyclic straining.