Bulky averaged microscopic information for ECAP-processed Cu using Accelerator-based gamma-ray-Induced Positron Annihilation Spectroscopy and neutron diffraction

Ishibashi, Toshihiro*; Tomota, Yo*; Sugaya, Satoshi*; Toyokawa, Hiroyuki*; Hirade, Tetsuya  ; Horita, Zenji*; Suzuki, Hiroshi  

Bulky averaged microstructural parameters like vacancy density, texture, intergranular stress, etc. 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 positron annihilation peaks of AIPAS increased by the first ECAP cycle and then decreased slightly with further ECAP cycles. Upon annealing, the S recovered at a lower temperature for the eight-cycle ECAP processed sample than for the one-cycle processed sample. The texture and intergranular stresses generated by ECAP are determined by neutron diffraction analyses. Changes in FWHM and intensity of neutron diffractions monitored in situ during annealing indicate the early onset of recrystallization in the eight-cycle ECAP sample. These bulky averaged data show good agreements qualitatively with local SEM/EBSD observations and the results of mechanical tests.