Thermomechanical processing enhances the toughness of aluminum alloys by refining grains, controlling recrystallization, and promoting beneficial precipitation. Optimizing these parameters improves strength–ductility balance, fracture toughness, and resistance to stress corrosion, making it an efficient and industrially viable approach for microstructural control.

To enhance the toughness of aluminum alloys through thermomechanical processing, careful tuning of deformation and heat treatment parameters is essential. It is known that toughness reflects an alloy’s ability to absorb energy and resist fracture, and it benefits from refined grain structures, optimized precipitate distributions and substructures that impede crack growth while preserving ductility. Some strategies to achieve this, focusing on controlling deformation, temperature, and microstructural features, and to minimize the strength-toughness trade-off are listed below:

1) Tailor the deformation sequence

• Control the multi-step deformation by careful combination of hot rolling, cold rolling, annealing, solution treatment, pre-aging, moderate deformation (10–50% strain) and final aging in a sequence known as final thermomechanical treatment (FTMT).
• Localized or Warm Forming: Use hot sheet metal forming or warm forming with pre-aged hardening for high-strength alloys like 7075. This enhances formability and toughness by controlling recrystallization and texture, particularly at room or elevated temperatures, while avoiding widespread recrystallization that could coarsen grains

2) Manage temperature and strain rate

• Deformation Temperature: Perform hot working at 200–500°C (above half the alloy’s melting point) to enable dynamic recovery through dislocation climb and annihilation, forming stable equiaxed subgrains. This increases ductility and toughness as temperature rises or strain rate decreases. Rapid quenching after hot working, as in press heat treatment to T5 temper, preserves strengthening substructures without excessive recrystallization.
• Strain Rate Control: Lower strain rates during rolling or extrusion promote grain refinement and texture control, reducing delamination and corrosion while enhancing fatigue resistance and toughness. High strain rates in processes like impact extrusion generate localized heating for precipitate dissolution, followed by quenching to lock in favorable microstructures.
• Aging Conditions: Apply pre-aging at or below standard aging temperatures (e.g., 120°C for 24–48 hours) to ensure uniform precipitate nucleation, competing with heterogeneous nucleation on dislocations. Multi-stage aging or over-aging reduces strength by 10–15% but widens PFZs and promotes discontinuous η(MgZn₂) precipitates, significantly improving fracture toughness in alloys like Al–Zn–Mg–Cu.

3) Engineer the microstructure specifically for enhanced toughness

• Grain Refinement and Bimodal Structures: Aim for fine grains (
  2 votes 2 thanks