Evaluation of anelasticity and plastic creep limit for alloy 800

Abstract

The elevated temperature tensile, anelastic and creep properties of a precipitation strengthened NiCr austenitic steel (alloy 800) have been evaluated with respect to LMFBR application. These properties have been estimated and formulated for small strains and temperatures on the order of 823 K. It has been shown that despite suppression of the in-service stresses to beneath the alloy's yield strength, plastic deformation will occur at such temperatures and the stress below which plastic strain is effectively zero (plastic creep limit) is negligible for a reactor life time. The plastic creep limit at a given time and temperature markedly depends on the degree of precipitation hardening or prior cold deformation for alloy 800. The contribution from anelastic deformation is less than 0.05% and only becomes important for strict dimensional control and constrained parts.