Ultra-Fine Grained Steel: Relationship Between Grain Size and Tensile Properties

Abstract

Characteristic ferrite grain growth occurs in parallel with the Ostwald ripening of cementite particles during annealing of submicron-grained ferrite/cementite steel with a heterogeneous and dense distribution of cementite particles. The applicability of the Hall-Petch relation to the hardness and average ferrite grain size is demonstrated as a predictive means to show a significant potential for hardening by grain refining. The lower yield stress, upper yield stress, and ultimate tensile stress tend to have monotonic relationships with the carbon content. True stress increases with increase in the carbon content. However, the strain-hardening rate increases when the carbon content is increased to 0.3 wt% C, after which the strain-hardening rate remains almost constant even with further increase in the carbon content. This strain-hardening is reflected in a similar change in terms of uniform elongation.