An overview of flow patterns development on disc lower surfaces when processing by high-pressure torsion

Stainless steel was selected to study the flow patterns developed with anvil misalignments of 100, 200 and 300 μm on the disc lower surfaces during processing by high-pressure torsion (HPT) through totals of up to 16 turns. A pair of anvils having a roughness of Ra ≈ 15 μm was utilized to investigate the flow pattern development. Discs subjected to only compression in HPT exhibit similar characteristics to the as-received material in the phase domains and there were no overall curvatures of the austenitic (γ) and ferritic (α) phases. Double-swirl flow patterns were not observed in the 1 turn sample but they appeared on the disc lower surfaces after 5 and 16 turns with all three-anvil alignment conditions. There was no significant difference in the double-swirl configuration size for the 5 and 16 turns samples with different amounts of anvil misalignments. These results have important implications for processing metals by HPT.