Combined contribution of Cu-rich precipitates and retained austenite on mechanical properties of a novel low-carbon medium-Mn steel plate

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.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.936.1283 ◽

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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Thermal stability of retained austenite and mechanical properties of medium-Mn steel during tempering treatment

Journal of Iron and Steel Research International ◽

10.1016/s1006-706x(17)30123-1 ◽

2017 ◽

Vol 24 (8) ◽

pp. 830-837 ◽

Cited By ~ 9

Author(s):

Xiao-li Zhao ◽

Yong-jian Zhang ◽

Cheng-wei Shao ◽

Wei-jun Hui ◽

Han Dong

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Retained Austenite ◽

Medium Mn Steel ◽

Tempering Treatment ◽

Mn Steel ◽

Thermal Stability Of

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A Novel Cyclic-Quenching-ART for Stabilizing Austenite in Nb–Mo Micro-Alloyed Medium-Mn Steel

Metals ◽

10.3390/met9101090 ◽

2019 ◽

Vol 9 (10) ◽

pp. 1090 ◽

Cited By ~ 2

Author(s):

Chunquan Liu ◽

Qichun Peng ◽

Zhengliang Xue ◽

Chengwei Yang

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Retained Austenite ◽

Volume Fraction ◽

Total Elongation ◽

Practical Significance ◽

Strengthening Effect ◽

Medium Mn Steel ◽

Cyclic Quenching ◽

Mn Steel

In the context of obtaining an excellent elongation and tensile-strength combination in the third generation of advanced high strength steel, we emphasized the practical significance of adjusting the retained austenite fraction and stability in medium-Mn steel to obtain better mechanical properties. A novel cyclic quenching and austenite reverse transformation (CQ-ART) was used to obtain a large retained austenite content in Fe-0.25C-3.98Mn-1.22Al-0.20Si-0.19Mo-0.03Nb (wt.%) Nb–Mo micro-alloyed medium-Mn steel. The results show that after twice cyclic quenching and ART, the alloy exhibited optimum comprehensive properties, characterized by an ultimate tensile strength of 838 MPa, a total elongation of 90.8%, a product of strength and elongation of 76.1 GPa%, and the volume fraction of austenite of approximately 62 vol.%. The stability of retained austenite was significantly improved with the increasing of the number of cyclic quenching. Moreover, the effects of CQ-ART on the microstructure evolution, mechanical properties, C/Mn partitioning behavior, and austenite stability were investigated. Further, the strengthening effect of microalloying elements Nb–Mo was also discussed.

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Effect of Annealing Processes on Microstructures and Mechanical Properties of Medium Mn Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.944.337 ◽

2019 ◽

Vol 944 ◽

pp. 337-343

Author(s):

Rui Dong ◽

Ke Lv ◽

Hui Guo ◽

Ai Min Zhao

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Retained Austenite ◽

Total Elongation ◽

Annealing Process ◽

Two Stage ◽

Two Phase ◽

Medium Mn Steel ◽

Significant Difference ◽

Mn Steel

Two annealing processes have been designed to process a medium Mn steel, namely, the traditional direct two-phase annealing process and the pre-quenching treatment before two-phase annealing process, called two stage annealing process. The experimental results indicated that different annealing processes resulted in completely different microstructures, and a significant difference in mechanical properties. The microstructures of the steel after direct two-phase annealing process were coarse tempered martensite matrix and retained austenite. In this case, the optimum mechanical properties with total elongation of 29.87 %, tensile strength of 932 MPa and UTS*TE of 27.84 GPa•% were achieved after annealing at 625 °C for 18 h. The annealing process with pre-quenching treatment could realize two kinds of retained austenite, including acicular austenite and blocky austenite. The process with pre-quenching treatment could improve mechanical properties as well as shorten the optimal annealing time. The steel with two stage annealing process achieved optimal mechanical properties after pre-quenching and annealing at 625 °C for 4 h with tensile strength of 1177 MPa, total elongation of 30.92 % and UTS*TE of 36.39 GPa•%.

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