THERMAL FATIGUE DISLOCATION STRUCTURES IN 316L STEEL: EXPERIMENTS AND SIMULATIONS

In an attempt to better understand damage accumulation mechanisms in thermal fatigue, dislocation substructures forming in 316L steel during a specific test are examined and simulated. Hence, thin foils taken out of massive, tested specimens are observed in transmission electron microscopy (TEM). These observations help in determining an initial dislocation configuration to be implemented in a 3D model combining 3D discrete dislocation dynamics simulation (DDD) and finite element method computations (FEM). It is found that the simulated mechanical behaviour of the DDD microstructure is compatible with FEM and experimental data. The numerically generated dislocation microstructure is similar to ladder-like dislocation arrangements as found in many fatigued f.c.c. materials. Distinct mechanical behaviour for the two active slip systems are shown and deformation mechanisms are proposed. Up to T=650K, no evidence for direct effect of temperature on climb and cross slip phenomenon was found