Achieve high plasticity and strength in 6016 alloy by high-pressure torsion combined with post-aging treatments

High-pressure torsion (HPT) processing currently receives much attention mainly because it can significantly improve the strength of alloys compare to other sever plastic deformation. However, a common problem for these HPT processed alloys is that they suffer from low plasticity. Here we proposed an optimized post-aging treatment that achieves HPT processed 6016 alloy with tensile elongation as large as ∼36% and ultimate tensile strength over 500 MPa. Through systematically comparing the effects of high and low temperature aging treatments on the microstructure and properties of alloys, it was found that low-temperature long-time aging treatment can make HPT processed 6016 alloy exhibit higher plasticity while maintaining higher strength. The higher strength mainly originates from finer grains and higher strengthening effect of L precipitates, while the higher plasticity is attributed to the formation of nanoscale Si particles with smaller size and distributed in the grain interior after low-temperature long-time aging treatment. In addition, thermo-kinetic calculation demonstrates that the low-temperature long-time aging treatment provides higher thermodynamic driving force, higher kinetic activation energy and higher generalized stability for L phase precipitation, which is conducive to achieve a good strength-plasticity combination of HPT processed alloys.