Significant Bauschinger effect and back stress strengthening in an ultrafine grained pure aluminum fabricated by severe plastic deformation process

Bauschinger test in uniaxial tension-compression mode was carried out for the first time on pure Al specimens having homogeneous ultra-fine grained (UFG) microstructures fabricated by equal-channel angular pressing (ECAP) and subsequent annealing processes. Significant stress (transient softening), energy parameter their strong dependences tensile plastic pre-strain at very early stage of deformation were measured UFG specimens, sharp contrast to coarse-grained (CG) counterpart. The grain size dependence effect qualitatively discussed terms back arising from formation dislocation pile-up against boundary during deformation.