Dislocation substructure in 316L stainless steel under thermal fatigue up to 650 K

In an attempt to investigate damage accumulation mechanisms in thermal fati gue, dislocation substructures forming in 316L steel during one specific te st were examined and simulated. Hence, thin foils taken out of massive, tes ted specimens were first observed in transmission electron microscopy (TEM) . These observations helped in determining one initial dislocation configur ation to be implemented in a numerical model, combining 3D discrete disloca tion dynamics simulation (DDD) and finite element method computations (FEM) . It was found that the simulated mechanical behaviour of the DDD microstru cture is compatible with FEM and experimental data. The numerically generat ed dislocation microstructure is similar to ladder-like dislocation arrange ments as found in many fatigued f.c.c, materials. Distinct mechanical behav iour for the two active slip systems was shown and deformation mechanisms w ere proposed. Up to T = 650 K, no evidence for direct effect of temperature on climb and cross slip phenomena was found. (C) 2001 Elsevier Science B.V . All rights reserved.