Effect of cryogenic and room-temperature rolling on the microstructural evolution and mechanical behavior of spray-formed 7055 Al-Zn-Mg-Cu alloy

Abstract

This study investigates the effects of room-temperature rolling (RTR) and cryogenic rolling (CR) on the microstructure, mechanical properties, and fracture morphology of spray-formed (SF) 7055 Al-Zn-Mg-Cu alloy, with a focus on the deformation across reductions ranging from 20 % to 80 %. Utilizing SF as the base processing technique, the study aims to overcome challenges associated with the alloy's high content during conventional casting, such as segregation, grain coarsening, and the formation of internal defects. The findings indicate that CR significantly enhances the ductility and refines the microstructure of SF-7055 Al alloy compared to RTR, particularly at higher reductions. CR prevents the formation of severe cracks and maintains higher ductility and texture intensity, which are crucial for the demanding applications of this alloy in aerospace and transportation sectors. Microstructural analysis reveals that CR achieves a more uniform deformation, effectively reduces shear band formation, and facilitates the formation of finer and more evenly distributed precipitates due to suppressed solute atom mobility at cryogenic temperatures. Mechanical testing shows that CR enhances strength and hardness at lower reductions by maintaining high dislocation density, which does not annihilate as rapidly as in RTR. Tensile fracture analysis further demonstrates that CR leads to smoother fracture surfaces and fewer macroscopic cracks, indicating a more controlled failure mechanism. This study underscores the potential of cryogenic processing in improving the performance and applicability of high-strength Al alloys, offering significant insights for industrial applications where material reliability and enhanced mechanical properties are critical.