Microstructure Evolution and In Situ Resistivity Response of 2196 Al-Li Alloy during Aging Process

The microstructure evolution of 2196 Al-Li alloy during aging was investigated by microhardness test, transmission electron microscope (TEM) analysis and in situ resistivity measurement. The results showed that the resistivity of the 2196 Al-Li alloy during aging rapidly decreased during the first few hours, and then gradually increased after reaching the minimum value, which is temperature-dependent. The microstructure of the alloy was dominated by the δ' phase after aging at 160 °C for 2 h while the T₁ phase could hardly be seen until it had been aged for 16 h. As the aging time went on, significant ripening appeared for the δ' phase while typical growth could be observed for the T₁ phase. The increase in the resistivity of the 2196 Al-Li alloy during aging was attributed to the stronger electron scattering capacity of the T₁ precipitation and the coupling effect between the T₁ and δ' phases.