Influence of Stacking Fault Energy on microstructures and mechanical properties of fcc pure metals by equal channel angular pressing

In the present work 99.98% commercial pure copper, 99.5% commercial pure nickel and 99.5% commercial pure aluminum are imposed on high strain levels of 24, 8 and 44 by equal channel angular pressing (ECAP) via route Bc, respectively. Mechanical properties and microstructures are investigated by microhardness tests and TEM observations. Results show that microhardness increase as strain increase up to a max value in copper after a strain level of 8, and then begin to decrease slightly, while the microhardness increase as strain increases in nickel until to a strain level of similar to 12, and as that in aluminum, microhardness increase as strain increase in a relative low strain level, and then reach an saturation value at a strain level of similar to 4. TEM results show that grain sizes of pure copper, pure nickel and pure aluminum have been severed refined from several tens of microns in as-annealed state into several hundreds of nanometers after ECAP processing, however, microstructure of copper are mainly consisted of equiaxed (sub) grains with illegible grains/subgrains boundaries after processed by ECAP, while it is featured as lamellar boundaries in that of pure nickel and is composed of elongated grains in that of pure aluminum underwent a same strain level of ECAP.