The hot deformation behavior of uniform fine-grained GH4720 Li alloy was studied in the temperature range from 1040 to 1130℃and the strain-rate range from 0.005 to 0.5 s^(-1) using hot compression testing.Processing maps were constructed on the basis of compression data and a dynamic materials model.Considerable flow softening associated with superplasticity was observed at strain rates of 0.01 s^(-1) or lower.According to the processing map and observations of the microstructure,the uniform fine-grained microstructure remains intact at1100℃ or lower because of easily activated dynamic recrystallization(DRX),whereas obvious grain growth is observed at 1130℃.Metallurgical instabilities in the form of non-uniform microstructures under higher and lower Zener-Hollomon parameters are induced by local plastic flow and primary γ' local faster dissolution,respectively.The optimum processing conditions at all of the investigated strains are proposed as 1090-1130℃ with 0.08-0.5 s^(-1) and 0.005-0.008 s^(-1) and 1040-1085℃ with 0.005-0.06 s^(-1).
