Study on the regulation of microstructure and triaxial mechanical properties of 2195 Al–Li alloy via variable-temperature multi-directional forging processes

ABSTRACT Designing an effective multi-directional forging (MDF) process path for 2195 Al-Li alloy to regulate its microstructure and enhance triaxial mechanical properties is crucial for ensuring the service reliability of critical structural components. This study proposed a variable-temperature multi-directional forging (VTF) process and systematically investigated the microstructural evolution mechanisms and the underlying enhancement mechanisms of triaxial properties of 2195 Al-Li alloy. The results demonstrate that the VTF-10U9S process (450 °C-3U3S + 380 °C-3U3S + 440 °C-4U3S) achieves significant grain refinement (average size: 23.5 μm) and fragmentation/dispersion of coarse secondary phases through synergistic control of temperature-strain paths. Reducing deformation temperature promotes dislocation multiplication and generates high shear stress, effectively fragmenting coarse secondary phases; simultaneously, the resulting dislocation networks act as an additional driving force during high-temperature deformation, facilitating dynamic recrystallization (DRX) while weakening texture. This process delivers optimal comprehensive properties: average ultimate tensile strength (UTS) and yield strength (YS) reach 583.1 MPa and 542.3 MPa respectively, primarily attributed to synergistic grain boundary and precipitation strengthening; the highest average elongation (7.3%) primarily originates from the synergistic effect between uniform fine-grained structures and dispersed secondary phases, where the homogeneous fine grains coordinate deformation and release localized stress concentration through the generation of numerous deformation bands (DBs). The combined effects of grain refinement, secondary phase dispersion, and texture weakening significantly reduce anisotropy. This work provides essential process guidelines and a theoretical foundation for microstructure regulation and mechanical property optimization in high-strength Al-Li alloy components.