Effect of upset pressure on texture evolution and its correlation to toughness in flash butt joints

Abstract

Effect of upset pressure on the weld zone microstructure, texture evolution and its effect on toughness were investigated. It was observed that an increase in upset pressure leads to a decrease in the heat-affected zone width and also the grain size as a result of recrystallisation. It was also observed that insufficient upset pressure leads to porosity in the joints. Electron backscattered diffraction study on the weld zone showed that an increase in the upset pressure resulted in a sharp rise in (110)[001] and (110) component. Shear deformation at the plate edges due to the constrained flow of material led to the evolution of Goss fibre component parallel to the fracture plane. The presence of Goss fibre components that are generated during welding as a result of upsetting operation played a critical role in decreasing the toughness at the weld zone compared to the parent material.