Study of Elasto-Plastic Anisotropic Response of Stainless Steel Weld Metal Using Neutron Diffraction

Current analytical techniques for simulating the generation of residual stresses within welded structures make approximations and simplifications relating to the mechanical properties of the weld metal. This is due to the paucity of knowledge on the anisotropic nature of weld metal. Consequently, the study of elastic and plastic anisotropy, within metals has been a subject of considerable interest to both experimentalists and modellers alike. This study investigates the elastic and plastic response of crystal lattice planes within single-pass and multi-pass austenitic steel weld metal using time-of -flight (TOF) neutron diffraction. As this material is often used for the fabrication of high temperature, pressure vessel components, it is important to understand the evolution of lattice strains within each set of planes during elastic and plastic loading. Neutron diffraction measurements were carried out for both single and multi-pass weld metal subjected to in-situ uni-axial tensile loading. The elastic response of individual reflections was recorded by diffraction measurements. All measurements were carried out at the ENGIN-X facility at ISIS, UK. The objective of the measurements was to determine the Young's modulus and characterise the elastic and plastic anisotropy of the weld metal. Measurements indicate a significant variation between the Young's modulus for the two materials, with values close to 210 GPa for the singlepass weld metal and 90-130 GPa for the multi-pass welds. These results are explained in terms of the texture of the welds.