Precipitate coarsening-induced plasticity: Low temperature creep behaviour of tempered SAE 52100

Hardened and tempered SAE 52100 under uniaxial compressive loading deforms even at temperatures well below the tempering temperature and compressive loads well below the yield strength. The origin of the observed creep is associated with the coarsening of the nanosized precipitates (cementite, χ and η). The local volume changes that occur near dissolving and coarsening carbides in the presence of a uniaxial load cause macroscopic dimensional changes. For such process the kinetics is governed by the volume diffusion of C atoms. The coarsening of precipitates located near grain boundaries has been observed by in situ heating experiments with transmission electron microscopy. The observed logarithmic time dependent plastic strain can be described by the coarsening-induced plasticity model developed in this paper that combines concepts from transformation induced plasticity and precipitate coarsening models.