Effect of strain-induced precipitation on the low angle grain boundary in AA7050 aluminum alloy

Effects of the particles induced by strain on dynamic recrystallization and microstructure of the AA7050 aluminum alloy were investigated during hot deformation using X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). Experimental results showed that partial recrystallized grains containing little sub-structure were produced during the solution treatment. Numerous particles were successfully obtained by the strain-induced precipitation during first-pass deformation at 573 K. The deformation promoted spheroidization and refinement of the precipitate particles. Then these particles pinned dislocations and grain boundaries inhibiting dynamic recrystallization during second-pass high-temperature deformation at 673 K and low angle grain boundary fraction was increased significantly to 83.8%. Furthermore, the tensile test indicated that microstructure with numerous low angle boundaries (LAGBs) and 5 μm sub-grains had increased the strength and ductility of the AA7050 aluminum alloy.

► Experimental two-pass deformation process is different from conventional rolling. ► Globular precipitates were accelerated to produce by first-pass deformation. ► Second-pass deformation produced low angle grain boundaries owing to precipitates. ► Microstructure with numerous sub-structures had increased strength and ductility.