2009 Volume 50 Issue 1 Pages 70-75
Cyclic deformation behavior of ultra-fine grained (UFG) Cu of 99.99% purity processed by equal-channel angular pressing was investigated. In tension-compression fatigue tests under strain control, UFG Cu showed cyclic softening. Shear bands were formed along the direction inclined by about 45° from the loading axis. Observations using an electron backscattering diffraction technique and transmission electron microscopy revealed that local grain growth took place in the shear bands and overall grains elongated along the shear direction. Cyclic softening can be understood as a result of dynamic grain coarsening occurred intensively in the strain localized shear bands.