New hot thermo-mechanical processing of heat treatable aluminum alloys

The paper introduces hot thermo-mechanical processing (HTMP) as an improvement over known thermo-mechanical routes for heat treatable aluminum alloys. For many high strength aluminum alloys the kinetics of precipitate dissolution during heating and their dispersion during cooling from the solution temperature reveals a noticeable hysteresis with some areas of essential preservation of the solid solution, evident even at low cooling rates. By employing HTMP in these areas, it is possible to achieve, in a single step and with low stress, intensive plastic deformation without fracture and other forming defects. When followed by immediate quenching and optimal aging, HTMP results in hardness and strength similar to T6 temper. On the other hand, depending on material and strain rate, different microstructures can be developed comprising partial or full dynamic recovery (DRV) or dynamic recrystallization (DRX). In particular, fully dynamically recrystallized ultra-fine grained microstructures were observed for some materials. In comparison with related characteristics of the known routes, improvements in ductility, strength and fatigue are demonstrated for some alloys of 2XXX, 6XXX and 7XXX series.