Thermodynamic investigation of alkali-metal-induced high temperature embrittlement in Al-Li alloys

Thermodynamic investigation has been carried out to study the alkali-metal-induced embrittlement in Al-Li alloys. The calculated results indicate that the alkali-metal-rich liquid phase causes HTE. A liquid phase forms from the solid fcc phase (most likely at grain boundaries) during cooling, resulting in the occurrence of the embrittlement and affecting the mechanical properties. The calculated results agree with the experimental data well. Through thermodynamic calculions, the embrittlement safe and sensitive zones have been determined with respect to alkali-metal content and processing temperature. The critical processing temperature has been obtained which provides an important industrial processing parameter to suppress fracture and embrittlement. It is suggested that the proper processing temperature should be chosen according to the alloy composition and grain refinement can reduce the HTE tendency in industry.