GH4169合金高温动态应变时效实验及模拟

To understand the influence of the dynamic strain ageing (DSA) phenomenon on the mechanical properties of GH4169 superalloy during heat treatment, experimental and modeling investigations of DSA were carried out for solid solution treated nickel-based GH4169 superalloy at elevated temperature. Uniaxial tensile tests at 620 ℃ with strain rates of 10^-2, 10^-3, and 10^-4 s^-1 were performed to characterize the DSA effect, and negative strain rate sensitivity and serrated yielding behaviours were identified. Through the use of a thermal activation based viscoplastic flow rule with the DSA effect incorporated, a one-dimensional constitutive model was established. The deformation resistance was divided into two parts, i.e., slip resistance and deformation resistance caused by DSA effect. Two internal variables, equivalent ageing time and waiting time, were introduced to describe the DSA effect, and a least-squares method was adopted for parameter fitting. Comparison show that the calculated results of the constitutive model were in good agreement with the experimental results. The slip resistance increased with the increase of strain rate, whereas the deformation resistance caused by DSA effect decreased with the increase of strain rate. It further indicates that the identified negative strain rate sensitivity is the result of the competition between DSA effect and normal rate effect in certain strain rate range.