An investigation of flow patterns and hardness distributions using different anvil alignments in high-pressure torsion

A super duplex stainless steel was selected as a model material to evaluate the origins of unusual double-swirl flow patterns that have been reported on the upper surfaces of discs processed by high-pressure torsion (HPT). The experiments were conducted by making changes in the anvil alignment prior to HPT processing. Experiments were conducted under two different conditions: using essentially a perfect anvil alignment and with an initial anvil misalignment of 100 μm. The experimental results show that no double swirls are visible on the surfaces of discs processed under conditions of perfect anvil alignment but double swirls become visible when processing with a misalignment of 100 μm. The presence of double swirls also affects the measured hardness distributions, and for a misalignment of 100 μm the hardness distribution along a diameter may be non-symmetric with respect to the centre of the disc.