A Unified Temperature‐Dependent Constitutive Model for Haynes 230 Alloy for High Temperature Fatigue and Creep Analysis

ABSTRACT The Haynes 230 alloy is a candidate structural material for the high‐temperature components in advanced nuclear and energy systems because of its excellent creep resistance and oxidation resistance. However, accurately modeling its inelastic behavior, including rate‐independent cyclic plasticity, rate‐dependent creep, and stress relaxation under multi‐axial loading and different temperatures, remains challenging. This study presents a temperature‐dependent unified constitutive model, in which the nonlinear kinematic hardening incorporates the thermally activated static recovery term. A Kocks–Mecking‐based rate‐regime transition links the plastic and viscous deformation regimes. Model parameters are determined via a hybrid calibration strategy: Elastic and hardening terms are directly calibrated, while static recovery parameters are inversely identified using the Bayesian inference method based on creep and relaxation test data. The model is validated against uniaxial tension, low‐cycle fatigue, creep, stress relaxation, and multiaxial notched specimen tests. The close agreement between predictions and experiments demonstrates the model's robustness and applicability for structural integrity assessment of high‐temperature components under complex thermomechanical conditions.