Regulation mechanism of aging behavior and mechanical properties of 2195-T34 Al-Li alloy at different stress levels

The effect of aging on the mechanical properties of the 2195-T34 Al−Li alloy at different stress levels was investigated. When the stress was below the high-temperature yield strength (YS), the YS and elongation (EL) of the low-stress aged (LSA) and stress-free aged (SFA) specimens were similar. When the stress exceeded the high-temperature YS, the ultimate tensile stress (UTS) and EL of the specimens (HSA specimens) decreased significantly. This decrease suggested that an increase in stress reduced the damage resistance of the material. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations showed that variations in the effect of stress on the material properties were attributed to the combined effect of internal precipitate characteristics and Cu-rich precipitates at the grain boundary. The increase in stress induced the segregation of Cu atoms at the grain boundaries to form Cu-rich precipitates, facilitating the formation of precipitation-free zones (PFZ) at the grain boundaries. In addition, Cu-rich precipitates could act as damage nucleation sites, reducing the ductility of the material.