Creep of an AISI 310 type stainless steel and its numerical simulation using the Öström-Lagneborg creep model

The creep behaviour of an AISI 310 type stainless steel was determined under constant load (stress range 80–320 MPa) at a temperature of 700°C. The stress exponent, n, monotonically increased with the applied stress from a value of 2.8 to 16. The activation energy for creep, Q c, measured at 170, 200 and 230 MPa over the temperature range 650–800°C, is 341 kJ/mol. An activation energy of this magnitude indicates that the alloying elements in this steel are involved in the recovery climb process of the dislocation network. A simple and practical simulation was made of the experimental creep results by using the Öström-Lagneborg creep model, and the results are compared to other independent models and experimental results. A good fit between the experimental results and the calculated strain-time curves can be obtained by adjustment of model parameters to out material. The applicability of the Öström-Lagneborg theory to the creep involving subgrain structure formation is evaluated in light of the elastic theories for subgrain boundaries and recent experimental findings. By considering only forest dislocations not incorporated in subgrain boundaries and introducing a subgrain structure function S g( t), the Öström-Lagneborg model is able to simulate the creep behaviour where a subgrain structure is formed during the creep test. Further refinement of the theory is suggested whereby an assessment is made of the dislocation network coarsening kinetics.