Continuous high-pressure torsion of pure Al and Al-2 wt% Fe alloy using multi-wires

The process of high-pressure torsion (HPT) is applied for grain refinement in a wire form of pure Al and an Al-2% Fe alloy. An earlier version of the continuous HPT (CHPT) was further developed in this study, so that two wires were processed simultaneously. The two wires were placed symmetrically along a circumferential direction so that the pressure was equally applied on the wires to allow a stable processing. Guiding holes were made at both the inlet and outlet sides of the grooves on the upper anvils so that no interference of the two wires occurs. As in the earlier version, the surface roughness of the upper grooves and lower grooves were made different. Thus, this difference causes a continuous material flow when the lower anvil is rotated with respect to the upper anvil due to the occurrence of more slippage with the upper anvil. The modified CHPT process was then performed using the upsized anvils having two grooves with a half circular cross section on the upper and lower anvils with 100-mm-outer and 94-mm-inner diameters. The grain size was reduced to ~ 1 μm for pure Al and ~ 400 nm for the Al-2% Fe alloy after rotation by a quarter turn. The tensile strength of 280 MPa was achieved in the Al-2% Fe alloy, and an equivalent strain of ~ 25 was introduced through this CHPT process. It is suggested that CHPT process with multi numbers of wires is feasible when the anvil diameter is enlarged.