Deformation behavior of high Cr ferritic steel upon abrupt stress loading

Microscopic deformation behavior after abrupt stress loading under several applied stresses was investigated at high temperature for ASME-P92 steel. The estimation method for elastic limit was proposed based on analyzing the deformation behavior. Instantaneous plastic strain was not observed upon the abrupt stress loading under the applied stress from 60 to 200 MPa. Anelastic deformation originating from martensitic lath structure was observed after abrupt stress increment and reduction. Deformation behavior for a short time after stress increment is consistent with that after stress reduction under a low applied stress, meaning that only the anelastic deformation occurs. Increasing applied stress, deformation upon after stress increment is faster for a short time than that after stress reduction, indicating that not only anelastic deformation but also plastic deformation occurs after the stress increment. The stress at which plastic deformation occurs immediately after stress increment can be used to the estimate elastic limit of the ASME-P92 steel. The estimated elastic limits at 873, 923, and 973 K were close to 0.01% proof stress obtained from conventional tensile tests.