Eliminating Anisotropy of 7085 Alloy Forgings via Temperature Combination Control During Two-Stage Multi-Directional Forging

Due to its high mechanical properties and low quench sensitivity, 7085 aluminum alloy is suitable for the aircraft industry. However, large cross-section forgings of 7085 alloy usually have over 40% anisotropy in mechanical behaviors, especially in the vertical direction. In this study, two-stage multi-directional forgings (MDFs) with different temperature combinations, isothermal medium-temperature composite MDF (MC-MDF) and isothermal hot MDF (H-MDF), were applied to 7085 aluminum alloy ingots. The results indicate that MC-MDF achieved anisotropy below 10% without losing ultimate tensile strength (UTS). Three-dimensional (3D) microstructure analysis suggested that the MC-MDF samples accumulated higher dislocation density and exhibited an enhanced recrystallization structure. The elongation of the vertical direction increased significantly, which lowered the directionality of MC-MDF and increased the effective utilization rate of forgings. Also, MC-MDF obtained a lower yield strength (YS) due to the forging temperature in exchange for higher work hardening and a ductility increase. The average 3D UTS, YS, and EL values of MC-MDF are 554 MPa, 472 MPa, and 13.4%, and the index value reflecting the anisotropy of EL decreased from 14.0% to 8.6% for H-MDF.