Hall-Petch Strengthening in Single Crystal Copper with High Conductivity During Cryo-ECAP

The deformation microstructure and texture evolution of single crystal copper after cryogenic equal channel angular pressing (Cryo-ECAP) process were characterized by optical microscope, scanning electron microscope, X-ray diffractometer, and electron backscatter diffraction. The mechanical properties and conductivity properties were analyzed. The microstructure transition mechanism and its effects on the mechanical properties and conductivity properties were discussed. Results show that the directional shear bands formed in the early stage of Cryo-ECAP process seriously affect the microstructure transformation during the subsequent deformation. With increasing the strain, a high-density dislocation pile-up is formed in the shear bands during deformation by route A, and the proportion of characteristic grain boundaries is increased. The dislocations in the shear bands during deformation by route B-C present strong interactions, and the orientation of shear bands is dispersed after the deformation by route C. After 6 passes of deformation, the strong {111}< 112 > texture forms in the microstructure of single crystal copper, the strength increases from 126.0 MPa to 400.2 MPa, and the conductivity remains of above 98%IACS. After Cryo-ECAP, the directional shear bands form in the texture and the high-density dislocations are produced. The entanglement of dislocations effectively prevents the dislocation slip, and therefore the grains maintain the characteristics of single crystal.

Automated summary

This study investigated the deformation microstructure and texture evolution of single crystal copper after cryogenic equal channel angular pressing (Cryo-ECAP) process. The results showed that the formation of directional shear bands during the early stage of Cryo-ECAP significantly affected the microstructure transformation. The analysis also revealed that the deformation route and strain had an impact on the formation of dislocations and grain boundaries. After 6 passes of deformation, strong {111}< 112 > texture formed in the microstructure, leading to an increase in strength while maintaining high conductivity.