Effects of rolling and heat treatment on hydrogen embrittlement in medium-Mn steel

The ultrafine-grained (UFG) duplex microstructure of medium-Mn steel consists of a considerable amount of austenite and ferrite/martensite, achieving an extraordinary balance of mechanical properties and alloying cost. In the present work, two heat treatment routes were performed on a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C (wt.%) to achieve comparable mechanical properties with different microstructural morphologies. One heat treatment was merely austenite-reverted-transformation (ART) annealing and the other one was a successive combination of austenitization (AUS) and ART annealing. The distinct responses to hydrogen ingression were characterized and discussed. The UFG martensite colonies produced by the AUS + ART process were found to be detrimental to ductility regardless of the amount of hydrogen, which is likely attributed to the reduced lattice bonding strength according to the H-enhanced decohesion (HEDE) mechanism. With an increase in the hydrogen amount, the mixed microstructure (granular + lamellar) in the ART specimen revealed a clear embrittlement transition with the possible contribution of HEDE and H-enhanced localized plasticity (HELP) mechanisms.

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Enhancing the resistance to hydrogen embrittlement of Al-containing medium-Mn steel through heavy warm rolling

Scripta Materialia ◽

10.1016/j.scriptamat.2019.02.009 ◽

2019 ◽

Vol 165 ◽

pp. 15-19 ◽

Cited By ~ 14

Author(s):

Yongjian Zhang ◽

Weijun Hui ◽

Jiaojiao Wang ◽

Ming Lei ◽

Xiaoli Zhao

Keyword(s):

Hydrogen Embrittlement ◽

Warm Rolling ◽

Medium Mn Steel ◽

Mn Steel

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Hydrogen embrittlement of a cold-rolled Al-containing medium-Mn steel: Effect of pre-strain

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2020.05.239 ◽

2020 ◽

Vol 45 (41) ◽

pp. 22080-22093

Author(s):

JiaoJiao Wang ◽

Weijun Hui ◽

Zhiqi Xie ◽

Zhanhua Wang ◽

Yongjian Zhang ◽

...

Keyword(s):

Hydrogen Embrittlement ◽

Medium Mn Steel ◽

Cold Rolled ◽

Mn Steel

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Physical simulation and dilatometric study of double-step heat treatment of medium-Mn steel

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-020-00144-9 ◽

2020 ◽

Vol 20 (4) ◽

Author(s):

A. Skowronek ◽

M. Morawiec ◽

V. Ruiz-Jimenez ◽

C. Garcia-Mateo ◽

A. Grajcar

Keyword(s):

Heat Treatment ◽

Retained Austenite ◽

Physical Simulation ◽

Isothermal Holding ◽

Heat Treatments ◽

Double Step ◽

Dilatometric Study ◽

Medium Mn Steel ◽

One Step ◽

Mn Steel

Abstract The work addresses physical simulation and dilatometric study of one-step and double-step heat treatments of medium-Mn steel designed for automotive sheets. The conventional one-step isothermal bainitic transformation was applied as the reference heat treatment. The newly implemented heat treatment consisted of isothermal holding in a bainitic region followed by additional holding of the material at reduced temperature also in the bainitic range. This step was added to refine the microstructure, which led to the stabilization of the retained austenite. Calculations of equilibrium state and non-equilibrium cooling and simulations of the developed thermal cycles were performed using the thermodynamic JMatPro software. The physical simulations of the heat treatment were performed in the dilatometer. The obtained samples were subjected to microscopic observations using light and SEM microscopy. One- and two-step heat treatments allowed to obtain bainitic structures with high contents of retained austenite. Lowering the temperature of one-step isothermal holding resulted in the bainite refinement and adjacent retained austenite. The increased Mn content in steel increased its susceptibility to form coalesced bainite resulting in the partial formation of thicker plates despite a decrease in a process temperature.

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