Creep behavior as dislocation climb over NiAl nanoprecipitates in ferritic alloy: The effects of interface stresses and temperature

Abstract

Based on creep mechanism of lattice self-diffusion controlled dislocation climb process in the high temperatures range (873–923 K), dislocation climb model for creep deformation is presented with elastic interaction of climbing lattice dislocation with coherent nanoprecipitate to estimate theoretically the temperature and size dependence of creep behavior in NiAl nanoscale precipitation-strengthened ferritic alloy. The significant factors governing creep threshold stress and activation energy are evaluated quantitatively, such as temperature, nanoprecipitate size and interface effect as well as the mismatch between nanoprecipitate and matrix. The results show that creep rate data obey a good power-law dependence on applied stress with stress exponent of 4. In the temperature region investigated threshold stresses ranging from 0.4 to 0.5 σO and creep activation energies from 260 to 300 kJ/mol are evaluated, which are reasonable for characterizing the power-law dislocation creep mechanism. Model predictions presented in this work show good agreement with experiments for this ferritic Fe–Cr–Ni–Al alloy.