Influence of Pressing Temperature on Microstructure Evolution and Mechanical Behavior of UltrafineGrained Cu Processed by EqualChannel Angular Pressing
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AbstractPure Cu was processed by ECAP at five different temperatures from room temperature (RT) to 523K. The influence of pressing temperature on microstructure evolution and tensile behavior was investigated in detail. The results show that as the ECAP temperature is increased the grain size and ductility both increase whereas the dislocation density and yield strength decrease. In the case of ECAP processing in the range of RT to 473K the mechanism governing microstructural refinement is continuous dynamic recrystallization (CDRX), whereas at 523K the mechanism changes to discontinuous dynamic recrystallization (DDRX). At higher ECAP temperatures, the kinetics of CDRX are retarded leading to a lower fraction of equiaxed grains/highangle grain boundaries and a higher fraction of dislocation cell structures. At 523K, DDRX induces a high fraction of equiaxed grains with a very low dislocation density which appears responsible for the observed high tensile ductility. The sample processed at 523K possessed a good combination of strength and ductility, suggesting that processing by ECAP at elevated temperatures may be a suitable alternative to RT ECAP processing followed by subsequent annealing.
