Thermal behavior of copper processed by ECAP with and without back pressure

Ya Li Wang, Rimma Ye Lapovok, Jing Tao Wang, Yuan Shen Qi, Yuri Estrin

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48 Citations (Scopus)

Abstract

Samples of electrolytic tough pitch (ETP) pure copper were subjected to 12 passes of Equal-Channel Angular Pressing (ECAP) at room temperature with and without back pressure. Subsequent annealing was performed to evaluate the influence of back pressure during ECAP on the thermal behavior of ultrafine-grained copper. The microstructural and hardness changes caused by annealing were characterized by orientation imaging microscopy (OIM) and microhardness measurements. The application of back pressure resulted in an earlier drop in hardness upon annealing, which is believed to be associated with a lower critical temperature for the initiation of recrystallization and a rapid coarsening of microstructure. Regardless of whether back pressure was applied or not, structure coarsening during short-time annealing of ECAP-processed copper was governed by discontinuous static recrystallization. This is seen as a result of microstructure heterogeneity. Analysis of recrystallization kinetics was carried out based on observations of the microstructure after annealing in terms of the Avrami equation. The magnitude of the apparent activation energies for recrystallization in the absence of back pressure and in the case of back pressure of 100 MPa was estimated to be 99 kJ/mol and 91 kJ/mol, respectively. The reasons for reduced activation energy in the case of processing with back pressure are discussed.
Original languageEnglish
Pages (from-to)21 - 29
Number of pages9
JournalMaterials Science and Engineering A: Structural Materials: Properties, Microstructure and Processing
Volume628
DOIs
Publication statusPublished - 2015

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