The Flow Stress of Unstable Austenitic Stainless Steel Accompanied by Deformation-induced Martensite

Abstract

The flow stress (σ) of unstable austenitic stainless steels is studied by comparing stable austenitic and martensitic stainless steels.
(1) The root of dislocation density (√ρ) obtained by X-ray analysis in stable γ-phase increases with strain (ε) and the expression of ε as a function of √ρ is parabolic.√ρ of γ phase mixed with deformation-induced martensite (α') increases with the root of α'phase volume fraction (V_α'^1/2) in addition to the above relation.
(2) σ of unstable steels is intermediate of the values caluculated by "equal stress model" and"equal strain model" and it becomes to take the values estimated by equal strain model with increase of α'-phase.In this case, the higher the strength of α' phase is and the larger the volume of α' phase is, the higher is the ununiformity of strain between γ and γ' phase. In the case that the strength of α' phase is almost the same, the smaller the volume of γ' phase is, the smaller is the ununiformity of strain between γ and α' phase.
(3) σ is affected not only by the volume but also by the strength of α' phase and inversely plastic flow depresses α'-transformation to inhibit the enhancement of higher σ values due to high strength of α'-phase.