New alloys of aluminum piston alloy made by adding more nickel to their usual composition. Bulk-forming of new alloys at ambient temperature by conventional methods is not possible. Therefore, the hot-compression deformation behavior of these alloys has been studied in this study. Based on the true stress-strain graphs obtained from the experiments, the constitutive model proposed for these alloys based on the Johnson-Cook model. Then this model is improved by considering the coupled effects of the parameters. The accuracy of the proposed models has been investigated using appropriate statistical analysis, and as a result, the accuracy of the presented models has been confirmed. The modified model, compared to original model, in addition to the higher accuracy, can predict the trend of changes in flow stress. The study of variations of the model coefficients shows that with an increasing nickel content in the alloy composition, the strength and the flow stress of the alloys increased intensely at all temperatures and strain rates. Also, by increasing the amount of nickel, the effect of the strain rate on flow stress is reduced
