Microstructure and Mechanical Properties of Medium Manganese Steel Plate with High Strength and Toughness

2016 ◽  
Vol 879 ◽  
pp. 2293-2299
Author(s):  
Ying Zou ◽  
Yun Bo Xu ◽  
Zhi Ping Hu ◽  
Xiao Long Yang ◽  
Xiao Dong Tan ◽  
...  

An intercritical annealing process was applied to a medium manganese steel plate (Fe-0.01C-5.3Mn-1.53Si) after the thermo-mechanical controlled processing (TMCP) and ultrafast cooling (UFC). The microstructures were observed by scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). The retained austenite was measured by XRD and mechanical properties were measured by uniaxial tensile and impact tests. The influence of different annealing temperature was compared and the relationship between microstructures and mechanical properties was investigated. Results showed that the microstructures of the medium manganese steel plate were characterized by ultrafine grained lath-like ferrite and retained austenite and the excellent mechanical properties could be obtained at the annealing temperature of 640°C for 5 h. The volume fraction of the retained austenite reached up to 21%, which could significantly increase the elongation compared with the traditional steel plate. The mechanical property results revealed that the steel possessed adequate ultimate tensile strength of 865MPa and excellent impact energy of 121J (-20°C). The outstanding combination of strength and toughness indicates that the steel has a bright application prospect.

2016 ◽  
Vol 879 ◽  
pp. 2144-2149
Author(s):  
Kai Zhou ◽  
Ying Zou ◽  
Yun Bo Xu ◽  
Zhi Ping Hu ◽  
Xiao Dong Tan ◽  
...  

Continuous annealing processes were applied to a 980MPa cold-rolled dual phase steel (Fe-0.11C-2.5Mn-0.5Si-0.4Cr) and the effect of continuous annealing temperature on microstructure and mechanical properties was investigated. The microstructures were observed and analyzed by optical microscopy (OM), scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). The mechanical properties were measured by uniaxial tensile tests. The results revealed that the steel is composed of a certain percentage of ferrite, martensite and perhaps a small amount of retained austenite as well. As the annealing temperature increased, the volume fraction of martensite reached to 67% from 48% and the morphology translated to lath-like from M/A island. As a consequence, the ultimate tensile strength (UTS) and yield strength had a moderate increase from 1070 to 1110 MPa and 580 to 640 MPa, respectively. Meanwhile, the fracture elongation rose to the maximum 12.6% firstly and then decreased to about 9.0%. The optimizing mechanical properties with UTS up to 1090 MPa, yield ratio about 0.54 and fracture elongation about 13% could be obtained at the annealing temperature of 790°C for 120s.


2021 ◽  
Vol 1035 ◽  
pp. 404-409
Author(s):  
Zhe Rui Zhang ◽  
Ren Bo Song ◽  
Nai Peng Zhou ◽  
Wei Feng Huo

In this study, a new Fe-6Mn-4Al-0.4C high strength medium manganese hot rolled steel sheet was designed. The influence mechanism of the intercritical annealing (IA) temperature on microstructure evolution and mechanical properties of experimental steel were studied by SEM and XRD. The experimental steel was held for 30 minutes at 640°C, 680°C, 720°C, 760°C, 800°C, respectively. When the annealing temperature was 640°C, cementite particles precipitated between the austenite and ferrite phase boundary. As the annealing temperature increased, the cementite gradually dissolved and disappeared, the fraction of lamellar austenite increased significantly. When the annealing temperature is 800°C, the coarse equiaxed austenite and ferrite appeared. The yield strength (YS) decreased, the product of strength and elongation (PSE) and total elongation (TE) both increased first and then decreased, while the ultimate tensile strength (UTS) showed the opposite trend. The experimental steel exhibited excellent comprehensive mechanical properties after held at 760°C for 30 min. The UTS was 870 MPa, the YS was 703 MPa, and the TE was 77 %, the PSE was 67 GPa·%.


Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 887 ◽  
Author(s):  
Caiyi Liu ◽  
Yan Peng ◽  
Ling Kong ◽  
Yanqiang Wang

An Fe-0.15C-1.2Si-5Mn-0.09Nb-0.08V-0.07Mo (wt.%) medium manganese steel that was subjected to a novel austenite reverted transformation (ART) annealing process. This paper is based on the conventional ART annealing process, and a deformation and ART annealing process is proposed. The influence of the deformation degree on the microstructure and grain size of the medium manganese steel was determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). The results show that the deformation had a great effect on the microstructure evolution and grain size. The microstructure of the medium manganese steel after the deformation and ART annealing process was consistent with the theory of austenite reverse transformation, i.e., the martensite reverse transformation into austenite occurred during the deformation and ART annealing process. The final microstructure was a mixture of martensite and austenite. As the deformation degree increases, the martensite gradually refines, and carbides precipitate in the lath martensite. The retained austenite is gradually transformed from very large to small and is distributed between the martensite laths. The results show that when deformation occurs in the austenite region, a small deformation can obtain more retained austenite.


2010 ◽  
Vol 654-656 ◽  
pp. 286-289 ◽  
Author(s):  
Sea Woong Lee ◽  
Kyoo Young Lee ◽  
Bruno C. De Cooman

Ultra-fine grained TRIP steels (UFG-TRIP) containing 6wt%Mn were produced by intercritical annealing. An ultra-fine grained microstructure with a grain size less than 1μm was obtained. The formation mechanism of the high volume fraction of retained austenite was investigated by dilatometry, XRD and magnetic saturation. The fraction of retained austenite was strongly dependent on the annealing temperature. The tensile properties were also found to be strongly influenced by the annealing temperature with poorer mechanical properties being observed at higher annealing temperatures. It was found that the stabilization of the retained austenite was both a composition and size-effect, made possible by the grain refinement due to the reversely transformed martensite.


2012 ◽  
Vol 52 (5) ◽  
pp. 868-873 ◽  
Author(s):  
Hai Feng Xu ◽  
Jie Zhao ◽  
Wen Quan Cao ◽  
Jie Shi ◽  
Cun Yun Wang ◽  
...  

2016 ◽  
Vol 850 ◽  
pp. 659-663
Author(s):  
Xiao Gang Li ◽  
Ai Min Zhao ◽  
Hong Hong Zheng ◽  
Shao Heng Sun ◽  
Hong Xiang Yin

The microstructure and mechanical properties of a medium manganese quenching and partitioning (Q&P) steel for automobile were investigated by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and mechanical property test. The grain size and recovery degree were greatly affected by annealing temperature normally. The result shows that the medium manganese steel after quenching and partitioning (Q&P) heat treatment exhibited good mechanical properties. The maximum tensile strength and yield strength was 1280MPa and 1421MPa at 600°C, respectively. Additionally, the product of strength and plasticity could reached to 40472MPa×% at 640°C. Annealing temperature also had a great influence on the volume of retained austenite which increases linearly with the rise of annealing temperature as well.


2019 ◽  
Vol 818 ◽  
pp. 82-86
Author(s):  
Xin Xu ◽  
Ren Dong Liu ◽  
Bao Yu Xu ◽  
Hong Liang Yi ◽  
Guo Dong Wang

In this work, a novel type of δ-TRIP steel was designed, and the content and stability of retained austenite in δ-TRIP specimens under different annealing processes were detected and studied, respectively. The volume fraction of austenite was determined by X-ray diffraction (XRD). The microstructure and mechanical properties were analyzed systematically. The results show that a complex microstructure composed of three phases (ferrite, bainite and retained austenite) was obtained in the δ-TRIP steel. With the increasing of annealing temperature, both retained austenite and bainite content in the specimen increased, while the carbon content in retained austenite decreased, leading to a poor stability for retained austenite. Both tensile and yield strength improved with the increasing of annealing temperature, while the elongation reduced. The feature of retained austenite led to an excellent combination of ductility and strength, which was better than traditional TRIP steel.


Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3081
Author(s):  
Lena Heemann ◽  
Farhad Mostaghimi ◽  
Bernd Schob ◽  
Frank Schubert ◽  
Lothar Kroll ◽  
...  

Medium manganese steels can exhibit both high strength and ductility due to transformation-induced plasticity (TRIP), caused by metastable retained austenite, which in turn can be adjusted by intercritical annealing. This study addresses the laser additive processability and mechanical properties of the third-generation advanced high strength steels (AHSS) on the basis of medium manganese steel using Laser Powder Bed Fusion (LPBF). For the investigations, an alloy with a manganese concentration of 5 wt.% was gas atomized and processed by LPBF. Intercritical annealing was subsequently performed at different temperatures (630 and 770 °C) and three annealing times (3, 10 and 60 min) to adjust the stability of the retained austenite. Higher annealing temperatures lead to lower yield strength but an increase in tensile strength due to a stronger work-hardening. The maximum elongation at fracture was approximately in the middle of the examined temperature field. The microstructure and properties of the alloy were further investigated by scanning electron microscopy (SEM), hardness measurements, X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and element mapping.


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