Redistribution of Grain Boundary Misorientation and Residual Stresses of Thermomechanically Simulated Welding in an Intercritically Reheated Coarse Grained Heat Affected Zone

Abstract

A study of the migration of the grain boundary misorientation and its relationship with the residual stresses through time immediately after the completion of a thermomechanical simulation has been carried out. After physically simulating an intercritically overheated welding heat affected zone, the variation of the misorientation of grain contours was observed with the electron backscatter diffraction (EBSD) technique and likewise the variation of the residual stresses of welding with RAYSTRESS equipment. It was observed that the misorientation of the grain contours in an ASTM DH36 steel was modified after the thermomechanical simulation, which corresponds to the measured residual stress variation along the first week of monitoring, with compressive residual stresses ranging from 195 MPa to 160 MPa. The changes in misorientation indicate that the stress relaxation phenomenon is associated with the evolution of the misorientation in the microstructure caused by the welding procedure. On the first day, there was a fraction of 4% of the kernel average misorientation (KAM) values at 1° misorientation and on the fourth day, there was a fraction of 7% of the KAM values at 1° misorientation.

Investigation of Microstructures and Tensile Properties of 316L Stainless Steel Fabricated via Laser Powder Bed Fusion

“…Generally, it is known that the dislocations in a polycrystalline material can either be geometrically necessary dislocations (GNDs) or statistically stored dislocations (SSDs) [55]. Localized shearing and lattice rotation occurs during plastic deformation, causing grain misorientations [59].…”

“…The 4.0 mm thick samples had higher KAM values than the 1.5 mm thick samples, demonstrating higher resistance to As observed in the KAM maps, the undeformed samples were mainly dominated by the blue color, indicating less lattice distortion. Yellow and orange spots were observed on these surfaces as well and could be attributed to residual stresses that developed during the rapid solidification process [13,37,55]. When subjected to the tensile loads, lattice distortion occurred, and thus, the change in color from blue to green and yellow.…”