Transformation kinetics of retained austenite in the tensile Lüders strain range in medium Mn steel

2019 ◽  
Vol 169 ◽  
pp. 1-5 ◽  
Author(s):  
Jiawei Ma ◽  
Haiting Liu ◽  
Qi Lu ◽  
Yong Zhong ◽  
Li Wang ◽  
...  
Keyword(s):  
Retained Austenite ◽  
Strain Range ◽  
Transformation Kinetics ◽  
Medium Mn Steel ◽  
Mn Steel ◽  
Kinetics Of

Kinetics of Solute Partitioning During Intercritical Annealing of a Medium-Mn Steel

2015 ◽  
Vol 46 (11) ◽  
pp. 4841-4846 ◽  
Author(s):  
H. Kamoutsi ◽  
E. Gioti ◽  
Gregory N. Haidemenopoulos ◽  
Z. Cai ◽  
H. Ding
Keyword(s):  
Intercritical Annealing ◽  
Solute Partitioning ◽  
Medium Mn Steel ◽  
Mn Steel ◽  
Kinetics Of

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

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.

Effect of Al on the Microstructure and Mechanical Properties of Hot-Rolled Medium-Mn Steel

2018 ◽  
Vol 941 ◽  
pp. 292-298 ◽  
Author(s):  
Ding Ting Han ◽  
Yun Bo Xu ◽  
Ying Zou ◽  
Zhi Ping Hu ◽  
Shu Qing Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Trip Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
Microstructure And Mechanical Properties ◽  
Medium Mn Steel ◽  
Hot Rolled ◽  
Mn Steel

The present investigation was made to study the effect of Al on the microstructure and mechanical properties of hot-rolled medium-Mn TRIP steel (abbreviated as Al-TRIP). As a contrast, a Si-added medium-Mn TRIP steel (abbreviated as Si-TRIP) was also studied. Addition Al in medium-Mn steel can raise Ac3 temperature, which will restrain austenite transformation and expand the two-phase region, promoting Mn and C elements enriched in austenite. In-depth microstructure and mechanical properties analysis were carried out for the hot-rolled Al-TRIP and Si-TRIP steels in this study. The microstructure was characterized by scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). Volume fraction of retained austenite was measured by D/max2400 X-ray diffractometer (XRD). A dual-phase microstructure consisting of ultra-fine grained intercritical ferrite (IF) and lath-like retained austenite (RA) with high mechanical stability was obtained after annealing at 630°C for 2h for Al-TRIP steel. As prolonging the intercritical annealing time, the stability of RA decreased primarily due to the increase of grain size. The tensile test results indicated that the Al-TRIP steel possessed a better combination of tensile strength and elongation compared to Si-TRIP steel. Excellent mechanical properties with yield strength of 790MPa, tensile strength of 1050MPa, total elongation of 35% and UTS×TEL of 39GPa·% was obtained for the Al-TRIP steel.

Effects of Retained Austenite Stability on Mechanical Properties of High Strength TRIP Steel

2012 ◽  
Vol 602-604 ◽  
pp. 287-293
Author(s):  
Zhi Feng Li ◽  
Ren Yu Fu ◽  
Qing Shan Li
Keyword(s):  
Mechanical Properties ◽  
Trip Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
High Strength ◽  
Tensile Tests ◽  
Transformation Kinetics ◽  
Austenite Stability ◽  
Kinetics Of ◽  
Strength And Ductility

Mechanical stability of retained austenite and its effect on mechanical properties of high strength TRIP steel were studied by means of OM, SEM, TEM, XRD, and mechanical testing after various heat treatments. Results revealed that the film-type retained austenite located between bainite laths with high carbon content showed gradual martensitic transformation with strain, demonstrating a good TRIP effect. Samples annealed at 800°C and held at 420°C showed an optimum value of strength and ductility product up to 18381.2MPa%. Transformation kinetics of the retained austenite were evaluated through tensile tests and fitted by the function y=0.86-0.86×exp(-Ax). The fitting results were good.

scholarly journals Metastable Austenite Transformation Kinetics of Medium-Carbon Silicon-Rich Steel during Partitioning in a Q & P Process

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 738
Author(s):  
Yuan Liu ◽  
Yan Han ◽  
Sheng Yin ◽  
Fei Zhao
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
Transformation Product ◽  
Transformation Process ◽  
Transformation Kinetics ◽  
Metastable Austenite ◽  
Tem Analysis ◽  
Medium Carbon ◽  
Austenite Transformation ◽  
Kinetics Of

In the present study, quenching and partitioning (Q & P) treatment of a medium-carbon silicon-rich steel was processed by a dilatometer. The volume fraction of the retained austenite at different partitioning times was determined by X-ray diffraction (XRD). The metastable austenite transformation process after different partitioning times was studied by a combination of dilatometry, XRD, and transmission electron microscopy (TEM). Analysis of the transformation kinetics of metastable austenite during partitioning by means of dilatometry and the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation was carried out. The results show that the volume fraction of retained austenite increases first and then decreases with the increase of the partitioning time. The transformation active energy Q = 141 kJ·mol−1 and the Avrami exponent n = 1. The transformation product of metastable austenite is needle-like bainite, which grows perpendicularly towards the boundary of the austenite. Finally, the blocky austenite was divided into lath-shaped forms.

Study on the Mechanical Stability of Retained Austenite in Cold-Rolled Medium-Mn Steel

2014 ◽  
Vol 936 ◽  
pp. 1283-1289
Author(s):  
Jun Hu ◽  
Wen Quan Cao ◽  
Jie Shi ◽  
Han Dong
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
Residual Austenite ◽  
Tensile Tests ◽  
Medium Mn Steel ◽  
Cold Rolled ◽  
Mn Steel ◽  
High Mechanical Stability

The mechanical stability of the retained austenite in the cold-rolled medium-Mn steel was studied. Tensile tests were carried out to measure the mechanical properties of the annealed steel. Scanning electron microscopy was applied to characterize the microstructure evolution during the tensile process; X-ray diffraction analysis was used to determine the residual austenite content in the deformed steel. It was found that the volume fraction of retained austenite gradually decreases with strain .The value of the stability coefficient of retained austenite k was small in the test steel, which indicated high mechanical stability of retained austenite. Due to TRIP effect, the high mechanical stability of the retained austenite strongly delays the onset of necking, which resulted in good comprehensive mechanical properties with ultrahigh strength and plasticity.

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