Probing Mesoscopic Strain Evolution during Creep Deformation: An In-Situ Neutron Diffraction Study

Abstract

ABSTRACTThe development of lattice strain was studied using in-situ time-of-flight neutron diffraction during constant-load tensile creep deformation of an austenitic 316FR stainless steel at 180, 240, and 300MPa at 873K (a power-law creep regime) with time resolution of 900 seconds. The macroscopic (global) and mesoscopic (lattice) strains were measured simultaneously during creep using an extensometer and neutron diffraction, respectively. The hkl-specific lattice strains were measured to gain insights into the plastic anisotropy at various stages of creep deformation (i.e., primary, secondary, and tertiary regimes). Furthermore, the creep-induced lattice strain behavior was compared to the result obtained from a quasistatic tension test at 873K. The lattice strain evolution in the axial direction (direction parallel to the tensile loading axis) during the primary and secondary creep (dislocation creep) is quite similar to the quasistatic case (slip). However, in the tertiary creep regime, the creep-induced lattice strain accumulation is smaller than the quasistatic case at a given total strain, except the (111) reflection.