Speaker
Description
Thermomechanical processing, particularly hot compression, is widely used to tailor the microstructural and mechanical properties of aluminium alloys. Hot compression behaviour is commonly interpreted through true stress–true strain curves and microstructural evolution, especially grain refinement and orientation relationships. The nature of the true stress–true strain response is strongly influenced by deformation parameters such as temperature, strain rate, and strain, while dynamic recrystallization is governed by the kinetics of dislocation motion under these thermomechanical conditions. In general, the characteristics of true stress–true strain curves are associated with dynamic recrystallization. However, in precipitation-hardenable alloys, the flow behaviour is also significantly affected by precipitate evolution, including changes in precipitate size and distribution. Moreover, thermomechanical processing of precipitation-strengthened alloys is challenging due to the increased risk of material failure.
In hot-compressed Al7068 alloy, TEM analysis showed a consistent increase in precipitate size with increasing temperature and decreasing strain rate. The precipitate size nearly doubled with a 100°C rise in temperature (at a strain rate of 1 s⁻¹) and increased approximately fourfold when the strain rate was reduced from 1 s⁻¹ to 0.001 s⁻¹. This variation in precipitate size closely correlates with changes in the flow stress of the deformed material. Furthermore, the evolution of precipitate phases during hot deformation promotes a more uniform distribution of phases throughout the alloy, which can significantly enhance the overall material properties.
Keywords: Precipitate evolution, Al7068, thermomechanical processing, TEM