FRACTURE SHEAR STRESS INCREASING OF ULTRA-FINE GRAINED COPPER BY HYDROSTATIC EXTRUSION

10.25712/ASTU.1811-1416.2026.01.013

Abstract

The effect of postprocessing by hydrostatic extrusion on the fracture shear stress during tensile testing of ultra-fine grained copper obtained by equal-channel angular pressing was investigated. The hydrostatic extrusion processing influence has a positive effect on the plastic characteristics of the material was shown. The fracture shear stress increasing leads to increase the tensile strength to 10% in the range of ε_HE=0..0.6, with a further increase of deformation value the tensile strength decreases due to deformation heating was revealed. The fracture surfaces were examined by scanning electron microscopy. The tensile strength to the fracture shear stress ratio value, at which the mechanism of tensile fracture changes from shear to the mechanism of normal separation, was determined. The deformation of the hydrostatic extrusion influence on the dimples size was estimated: the mean dimples diameter raising almost twofold, which indicates an increase in the material viscosity. Structural changes in the material were studied by transmission electron microscopy. The axial texture during the hydrostatic extrusion process was formed, which leads to fracture shear stress and tensile strength increasing.