Bulky Averaged Microscopic Information for ECAP-Processed Cu Using Accelerator-Based Gamma-Ray-Induced Positron Annihilation Spectroscopy and Neutron Diffraction

Abstract

Bulky averaged microstructural parameters such as vacancy density, texture and intergranular stress for 99.99% Cu subjected to equal-channel angular pressing (ECAP) were investigated using accelerator-based gamma-ray-induced positron annihilation spectroscopy (AIPAS) and neutron diffraction. The Doppler-broadening parameter S for the AIPAS positron annihilation peaks increased after the first ECAP cycle and then decreased slightly with additional ECAP cycles. When the samples were annealed, the S value for the sample subjected to eight ECAP cycles was found to decrease at a lower temperature than that for the sample subjected to one ECAP cycle. The texture and intergranular stresses generated by ECAP were determined by neutron diffraction analyses. Changes in full width at half maximum and intensity of the (111) and (200) neutron diffraction peaks monitored in situ during annealing indicated the early onset of recrystallization in the sample subjected to eight ECAP cycles. These bulky averaged data show good agreement with both local scanning electron microscopy/electron backscatter diffraction observations and the results of mechanical tests.