Residual Stress Measurement of Centrifugally Cast Duplex Stainless Steel by Neutron Diffraction

Abstract

In ferrite-austenitic duplex stainless steels, due to different coefficients of thermal expansion and elastic moduli between the two phases, phase stresses will evolve during a thermal history of material processing such as casting, forging and annealing. Because residual stress possibly affects the material properties such as fatigue strength, welding stability and so on, residual stress measurement is considered necessary for the application of these multipahse materials. In this study, residual stress distribution along thickness direction of duplex stainless steel hollow cylinders fabricated by centrifugal casting was measured by pulsed neutron diffraction using time-of-flight (TOF) method at Japan Proton Accelerator Research Complex (J-PARC). In order to conduct triaxial stress analysis, strain-free lattice constants of both phases were measured from electropolished thin plates with thickness of lower than 90 micrometer, nearly equal to the grain size of austenitic phase. Based on the measurement results, the mechanism of stress development during centrifugal casting and effect of stress relief heat treatment (SRHT) was discussed.