Sharif Digital Repository

In this study, a dislocation-based model is presented for investigating the evolution of micro structure and mechanical properties of thin films during a wide range of straining. The model is applied to the High Pressure Torsion (HPT) process of thin nickel disks that provides valuable information on the evolution of material parameters during deformation. The model considers a free surface theory for thin films and can explain the size effect phenomenon in agreement with previous reported trends in literature  

Using flake powder metallurgy (FPM) technique, combined with high pressure torsion, super high strength-ductile Cu-CNT nanocomposite with high electrical conductivity is developed. The nanocomposite with 4 vol% CNT showed high tensile strength of ~474 MPa, high electrical conductivity of ~82.5% IACS as well as appreciable ductility of ~11%. According to microstructural studies, the excellent properties of the nanocomposite are attributed to the formation of trimodal grains, high density of twin and low angle grain boundaries, improvement in CNT and Cu interfacial bonding, and appropriate distribution and maintaining the microstructure of the nanotubes in the production process. The results... 

In this study, ultra-fine grained Cu and Cu + carbon nanotube (CNT) nanocomposites were prepared through a processes combining flake powder metallurgy, hot pressing, and high-pressure torsion (HPT). The effects of grain refinement and CNT reinforcement on the microstructure, hardness, wear resistance, and corrosion behavior of the newly developed nanocomposites were investigated. The results indicated that the HPT process decreased the grain size of Cu and Cu + CNT by 67.7% and 68.1%, respectively, and increased their microhardness by 151% and 132%. The addition of CNTs substantially improved the tribological behavior of Cu by generating a mechanically mixed carbon- and oxide-rich layer.... 

In this study, an attempt has been made to fabricate Cu-SiC nanocomposites by flake powder metallurgy and high-pressure torsion processing techniques at room temperature. Pure Cu and a mixture of Cu and nano-sized SiC powders were mechanically milled separately for 3 h and then green compacts were prepared by uniaxial pressing under 1 GPa pressure. The green compacts experienced 6-turn high-pressure torsion under a pressure of 6 GPa to prepare bulk Cu and Cu-SiC samples. The microstructures of the consolidated samples were characterized using an X-ray diffractometer and a high resolution scanning/transmission electron microscope, and the mechanical properties were evaluated by microhardness,...