In Situ Determination of Phase Stress States in an Unstable Medium Manganese Duplex Steel Studied by High-Energy X-ray Diffraction

Abstract

Duplex medium Mn steels are high-potential advanced high-strength steels (AHSS) for automotive construction. Their excellent forming properties stem from the specific stress partitioning between their constituting phases during deformation, namely the ferritic matrix, unstable retained austenite, and strain-induced fresh martensite. The stability of the retained austenite and the 3D stress tensors of each phase are determined simultaneously in this work by in situ high energy X-ray diffraction on synchrotron beamline during a tensile test. The role of internal stresses inherited from the manufacturing stage are highlighted for the first time as well as new insights to understand the origin of the serrations shown by these alloys.

In-situ strain induced martensitic transformation measurement and consequences for the modeling of medium Mn stainless steels mechanical behavior

“…However, they lead to inaccurate estimations since local hardening due to mechanical polishing can induce martensite transformation and thus overestimate the martensite volume fraction. X-rays diffraction is probably the most widely used method [7][8][9][10]. This technique has also been used to estimate the retained austenite volume fraction in TRIP steels [11,12].…”

“…Electron or neutron diffraction can also be used. Except for neutron and high energy X-rays available in synchrotron [8][9][10], diffraction techniques lead only to a surface evaluation of the martensite fraction. In-situ evaluations during strengthening with these methods are on the other hand hardly implemented.…”

Advanced Multiphase Steels

“…The manuscripts gathered in this Special Issue are committed to a variety of steel grades, embracing DP (Dual Phase) steels [1], medium-Mn steels [2,3], CFB (Carbide Free Bainitic steels) [4], nano-bainitic cast steel [5], δ-TRIP (TRansformation Induced Plasticity) [6] and precipitation hardened ferritic stainless steel [7].…”

Neutron and X-ray Diffraction Analysis of Macro and Phase-Specific Micro Residual Stresses in Deep Rolled Duplex Stainless Steels

“…These compressive RS can impede crack initiation and propagation; hence, in most cases they are regarded as beneficial for technical applications [ 7 , 8 , 9 ]. However, for coarse multiphase materials such as duplex stainless steels, the appropriate assessment of RS induced by means of post treatments requires the separation of micro and macro RS, since, in these cases, the material’s load bearing capacity strongly depends on the load partitioning on the phases under applied load and on the phase-specific mechanical behaviour [ 10 , 11 , 12 , 13 , 14 ]. Hence, for the assessment of the stress susceptibility of duplex stainless steels, knowledge on the phase-specific RS induced by the manufacturing or post treatment is essential.…”