The superposition of flow stress contributions in a precipitate hardened Ni-based alloy studied by strain rate sensitivity measurements Original Research Article

The strain rate sensitivity of the flow stress of underaged, peakaged and overaged samples of the γ′-hardened Ni-based superalloy Inconel X-750 has been measured. The experimental data are presented in the form of Haasen plots, which help to analyze the flow stress superposition rules. It was found that a progressive increase of the slope in the Haasen plot, during Stage II of work hardening, is correlated with the increase in the γ′-precipitate size. The analysis of the results was carried out in the framework of the theory developed by Kocks, Argon and Ashby (Kocks UF, Argon AS, Ashby MF. Prog Mater Sci, 1975;19:1) for two contributions to the flow stress. It was found that the square superposition rule leads to a slight curvature but more important, it predicts an increase of the effective slope in the Haasen plots in agreement with the experimental results.