Impact Toughness and Dynamic Compression of Ultrafine-Grained Pure Copper Produced by Equal-Channel Angular Pressing

This work presents studies the effect of ultrafine-grained (UFG) structure on Impact toughness and dynamic compression of pure copper MI (99.9%). The UFG structure was provided by means of equal-channel angular pressing (ECAP) on the Conform scheme with four and eight passes. Impact toughness tests on samples with U-shaped notch were performed using a drop weight impact machine. Dynamic compression test of cylindrical samples were performed with a setup with the Split-Elopkinson pressure bar (SHPB-20) by the Kolsky method. The results showed that the impact toughness of the UFG copper states was not less than that of the coarse-grained (CG) counterpart. Moreover, the fracture process of the UEG material requires more energy. An increase of compression strain rate by 6 orders resulted in the well-known strain-rate dependence of the yield strength for the CG material and the UFG material after eight ECAP passes. The yield strength of the material after four ECAP passes remained at the level corresponding to a quasi-static loading.