چكيده به لاتين
Abstract:
Severe Plastic Deformation (SPD) methods are kind of metal forming processes in which enhanced mechanical properties can be achieved by imposing large plastic deformation to a raw material. In this study, a novel combined process has been introduced for imposing large plastic deformation to initial Al wires. In the proposed method, the annealed wires were twisted to different pitch lengths and then pressed into an equal channel angular die of 170 degree with the aim of 6 rolls. Firstly, different parameters of the process were investigated by finite element method. Then, the effects of pure torsion and combined deformation method on the mechanical and microstructures of processed wires have been experimentally investigated. Results show that by achieving 15mm pitch length by torsion deformation, the ultimate tensile strength of raw material increased about 50%. Beside elongation of the deformed wires decreased to 2.8% from 22% compared to the annealed one. Other results indicate that by pressing the twisted wires into the ECAP-die channel, the elongation of specimens will increase significantly. For the 15mm pitch length wires, after four passes of pressing into the die channel, the elongation will increase to 7.8%. Microstructure images of twisted wires show that by applying torsion deformation grains will elongate into the direction of maximum shear stress. Also, these images revealed that the grain size on the surface layer of wires will experience a higher level of refinement in comparison to the grains at the wire center. By pressing the twisted wires into the die channel grains will elongate in the longitude direction on the surface layer and grain size will decrease at the wire center.
Keywords: plastic deformation, Al wire, tensile test, microstructure, microhardness test
