Prediction of transition stress in solution hardened alloys at high temperatures by flow stress predicting method

The stress exponent, n, which is the slope in a log σ-log (d/ε/dt) curve is about 3 in the intermediate stress range (region M) in the steady state deformation characteristics at high temperature in a solid solution hardened alloy. In the higher stress range (region H) and lower stress range (region L), however, the stress exponents are larger than those in region M. In this paper, the upper transition stress (σ_U) between regions M and H and the lower transition stress (σ_L) between regions M and L for f.c.c. Al-Mg and b.c.c. Fe-Mo alloys are calculated using the flow stress predicting method and compared with the experimental results. It is found that the predicted transition stress σ_U or σ_L almost agree with the experimental one. The flow stress prediction method based on the solute atmosphere drag mechanism should be applied on the stress range from σ_L to σ_U.