Abstract: To understand the forming behaviour of aluminum alloys,the upsetting test of alu-minum alloys al evaluated temperature is conducted.Because in warm forging the flow stress decreases with increasing straining,which is so-called work softening,no appropriate material formulation is available.For the evaluation of flow stress of aluminum alloys in warm forging processes,in this paper,a formula is derived by analyzing the stress data measured at various temperatures.It is demonstrated that the formula fits the flow stress obtained from experiment.

Key words: aluminum alloy, flow stress, warm forging,