Strength, grain refinement and solute nanostructures of an Al–Mg–Si alloy (AA6060) processed by high-pressure torsion

The effects of high-pressure torsion (HPT) processing on an Al–Mg–Si alloy (AA6060) have been investigated comprehensively. We show that the processing temperature has complex effects on the strength, grain refinement and solute nanostructures of the alloy. Ten-revolution HPT processing at room temperature produced the highest yield strength of 475 MPa, which is similar to a high-strength Al alloy. However, processing at 100 °C produced the finest grains due to the strong solute segregation to grain boundaries and the formation of high-density precipitates that pin grain boundaries. Processing at 180 °C led to significant decomposition of the alloy and the formation of coarse precipitates. This research demonstrates that solute nanostructures provide key information for unravelling the origins of HPT-induced strengthening and grain refinement, and reveals the important opportunities for “engineering” solute nanostructures to enhance grain refinement in HPT processing.