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Effects of Si addition on mechanical properties of severely deformed copper by accumulative roll-bonding (ARB) have been investigated. Tensile tests and strain-rate jump tests have been carried out at room temperature. For annealed coarse-grained polycrystals, the difference in yield stress σ between pure copper and a Cu-1.64at.%Si alloy was only about 15 MPa while the difference became 170 MPa after the ARB process by six cycles. The strain-rate sensitivity m of pure copper increased with increasing the number N of the ARB cycles for N ≥ 5. However, the increase in m becomes less significant for Cu-Si alloys. These findings have been discussed in terms of thermally activated dislocation processes. [ABSTRACT FROM AUTHOR]

Tensile tests and strain-rate jump tests were carried out at several temperatures below room temperature on Cu processed by accumulative roll-bonding (ARB). The temperature dependences of the flow stress and the activation volume were determined. In contrast to conventional coarse-grained materials where the activation volume increases with increasing temperature, the ARB processed copper by 8 cycles with ultrafine-grains showed inverse temperature dependence of activation volume, i.e., decreased activation volume with increasing temperature. This inverse temperature dependence of the activation volume is discussed in terms of thermally activated dislocation bow-out from grain-boundaries. [ABSTRACT FROM AUTHOR]

The dislocation density of pure copper fabricated by two severe plastic deformation (SPD) processes, i.e., accumulative roll bonding and equal-channel angular pressing, was evaluated using scanning transmission electron microscopy/transmission electron microscopy observations. The dislocation density drastically increased from ~ 10 13 m − 2 to about 5 × 10 14 m − 2 , and then saturated, for both SPD processes. [ABSTRACT FROM AUTHOR]