Advancement of microstructural evolution and deformation mechanisms in AA6082 aluminum alloy under elevated-temperature tensile loading

Abstract

This study explores the intricate interplay between strain-induced precipitation (SIP) and the underlying mechanisms that govern hot deformation in AA6082 aluminum alloy. Uniaxial tensile tests were conducted at elevated temperatures, ranging from 200 °C to 400 °C, and varied strain rates from 0.01 s−1 to 10 s−1. Employing advanced methodologies such as scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), energy dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM), the research investigates the relationship between deformation, precipitation, and structural evolution. At lower strain rates, longer deformation times promote dynamic recrystallization, thereby promoting the growth of substructures with enhanced ductility. On the contrary, at higher strain rates (10 s−1), shorter deformation times inhibit such processes, resulting in a clear predominance of dislocation motion along specific slip systems and consequently influencing the mechanical response of the alloy. The results also reveal temperature-dependent deformation mechanisms, such as intragrain slip, continuous dynamic recrystallization (CDRX), and SIP phenomena, which influence the alloy's mechanical response. At 200 °C, prominent work hardening dominates, while 400 °C exhibits dynamic softening mechanisms. EBSD analysis elucidate temperature-specific deformation mechanisms, including intragrain slip at 200 °C and transitional phenomena at 300 °C. Microstructural analysis at 200 °C reveals the absence of needle- or rod-shaped precipitates. On the contrary, at 300 °C, the presence of β/β' precipitates significantly influences the nucleation of β'' precipitates at the grain boundaries. At 400 °C, substantial rod-shaped β' phase precipitates appear, demonstrating a complex interplay between diffusion mechanisms and strain-induced effects. In addition, the study also investigated the fracture behavior of aluminum alloy at different tensile temperatures, revealing the transition from transgranular fracture at 200 °C to intergranular fracture at 300 °C, as well as the shear effect of β/β' phase precipitates at this temperature. The findings provide a comprehensive understanding of the alloy behavior under diverse conditions, essential to optimize its processing parameters and mechanical properties.