Thermal Stability of Ultra Fine Grained Copper Prepared by High Pressure Torsion Using Various Pressures

Abstract

Two samples of ultra fine grained copper were prepared by high pressure torsion using two different pressures of 3 GPa and 6 GPa. The higher pressure resulted in an ultra fine grained structure with a smaller grain size and higher density of defects compared to the sample prepared with the lower pressure. We compared thermal stability of ultra fine grained structure for both samples. Microstructure investigations were performed by positron lifetime spectroscopy combined with X-ray diffraction and transmission electron microscopy. Firstly microstructure of the asprepared samples was characterized. Subsequently the samples were subjected to isochronal annealing and evolution of microstructure with annealing temperature in both samples was compared. We have found that the sample prepared using the higher pressure exhibits a lower thermal stability.

Structural investigations of submicrocrystalline metals obtained by high-pressure torsion deformation

“…UFG Cu + 0.5 wt.% Al 2 O 3 , the free positron component was not detected and saturated positron trapping at defects occurs. A decrease of defect density and grain growth with increasing temperature during isochronal annealing lead to rise of the intensity of the free positron component [13,14]. The second component is dominating and comes from positrons trapped at dislocations.…”

<i>In Situ</i> X-Ray Diffraction Study of Thermal Stability of Cu and Cu-Zr Samples Processed by ECAP

“…Studies of this stability for Cu and/or Cu alloys have also been published for both ECAP (e.g. [4][5][6]) and HPT [7][8][9][10][11] samples. Thermal stability of fcc metals processed by different methods of severe plastic deformation was studied in [12].…”

“…In order to stabilize the fine-grained microstructure, small amount of other compounds are added like Al 2 O 3 [e.g. 10,11] or Zr.…”

Influence of Severe Plastic Deformation on the PLC Effect and Mechanical Properties in Al 5XXX Alloy

“…Severe plastic deformation (SPD) is an effective method for producing bulk nanostructured materials. Several methods are applied to reduce grain size by deformation such as extrusion (recently the most popular is hydrostatic extrusion HE [1,2]), Cyclic Extrusion Compression (CEC) [3], Equal-Channel Angular Extrusion (ECAE) [4] or Equal-Channel Angular Pressing (ECAP) [5,6,7,8] , Accumulative Roll-Bonding (ARB) [9,10,11], and High Pressure Torsion (HPT) [12,13].…”