scholarly journals Thermal Stability of Retained Austenite and Properties of A Multi-Phase Low Alloy Steel

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 807 ◽  
Author(s):  
Zhenjia Xie ◽  
Lin Xiong ◽  
Gang Han ◽  
Xuelin Wang ◽  
Chengjia Shang
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
Low Carbon ◽  
Low Alloy Steel ◽  
Multi Phase ◽  
Thermal Stability Of

In this work, we elucidate the effects of tempering on the microstructure and properties in a low carbon low alloy steel, with particular emphasis on the thermal stability of retained austenite during high-temperature tempering at 500–700 °C for 1 h. Volume fraction of ~14% of retained austenite was obtained in the studied steel by two-step intercritical heat treatment. Results from transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicated that retained austenite had high thermal stability when tempering at 500 and 600 °C for 1 h. The volume fraction was ~11–12%, the length and width remained ~0.77 and 0.21 μm, and concentration of Mn and Ni in retained austenite remained ~6.2–6.6 and ~1.6 wt %, respectively. However, when tempering at 700 °C for 1 h, the volume fraction of retained austenite was decreased largely to ~8%. The underlying reason could be attributed to the growth of austenite during high-temperature holding, leading to a depletion of alloy contents and a decrease in stability. Moreover, for samples tempered at 700 °C for 1 h, retained austenite rapidly transformed into martensite at a strain of 2–10%, and a dramatic increase in work hardening was observed. This indicated that the mechanical stability of retained austenite decreased.

scholarly journals Mechanical and thermal stability of retained austenite in plastically deformed bainite-based TRIP-aided medium-Mn steels

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Aleksandra Kozłowska ◽  
Adam Grajcar ◽  
Aleksandra Janik ◽  
Krzysztof Radwański ◽  
Ulrich Krupp ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Retained Austenite ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Mechanical Stability ◽  
Electron Backscatter Diffraction ◽  
Cost Effective ◽  
Tensile Tests ◽  
Thermal Stability Of

AbstractAdvanced medium-Mn sheet steels show an opportunity for the development of cost-effective and light-weight automotive parts with improved safety and optimized environmental performance. These steels utilize the strain-induced martensitic transformation of metastable retained austenite to improve the strength–ductility balance. The improvement of mechanical performance is related to the tailored thermal and mechanical stabilities of retained austenite. The mechanical stability of retained austenite was estimated in static tensile tests over a wide temperature range from 20 °C to 200 °C. The thermal stability of retained austenite during heating at elevated temperatures was assessed by means of dilatometry. The phase composition and microstructure evolution were investigated by means of scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and transmission electron microscopy techniques. It was shown that the retained austenite stability shows a pronounced temperature dependence and is also stimulated by the manganese addition in a 3–5% range.

Research of Recrystallization Processes in Low-Carbon Low-Alloy Steel in Modeling High-Temperature Rolling

2019 ◽  
Vol 10 (6) ◽  
pp. 1301-1308 ◽  
Author(s):  
S. V. Korotovskaya ◽  
O. V. Sych ◽  
E. I. Khlusova ◽  
E. A. Yashina
Keyword(s):  
High Temperature ◽  
Alloy Steel ◽  
Low Carbon ◽  
Low Alloy Steel

Effect of Ausforming Temperature on Bainite Transformation of High Carbon Low Alloy Steel

2015 ◽  
Vol 817 ◽  
pp. 454-459 ◽  
Author(s):  
Jian Guo He ◽  
Ai Min Zhao ◽  
Huang Yao ◽  
Chao Zhi ◽  
Fu Qing Zhao
Keyword(s):  
Low Temperature ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Transformation Rate ◽  
Low Alloy Steel ◽  
High Carbon ◽  
Bainite Transformation ◽  
Electron Backscattered Diffraction ◽  
In Situ Experiments

The effect of ausforming temperature on bainite transformation of high carbon low alloy steel was studied by in situ experiments using a Gleeble 3500 thermal and mechanical testing system. Morphology and crystallography of ausforming bainite were examined by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It has been found that deformation at all temperatures range from 230°C to 600°C can accelerate low temperature bainite transformation, and transformation rate increased with deformation temperature reduced. Quantitative X-ray analysis shows that the volume fraction of retained austenite was about 35.84% after deformation and isothermal transformation for 20 hours, it was approximately the same amount with austempering bainite transformation process (no strain) which austenite volume fraction was about 32.01%. Low temperature bainite formation can be accelerated with a smaller increase amount of retained austenite by deformation at a low temperature range of 230~600 oC.

scholarly journals Thermal Stability of Nanocrystalline Structure In X37CrMoV5-l Steel

2015 ◽  
Vol 60 (1) ◽  
pp. 511-516 ◽  
Author(s):  
E. Skołek ◽  
S. Marciniak ◽  
W.A. Świątnicki
Keyword(s):  
Thermal Stability ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
Nanocrystalline Structure ◽  
Thin Layers ◽  
Isothermal Quenching ◽  
Initial Stage ◽  
Increasing Temperature ◽  
Thermal Stability Of

AbstractThe aim of the study was to investigate the thermal stability of the nanostructure produced in X37CrMoV5-1 tool steel by austempering heat treatment consisted of austenitization and isothermal quenching at the range of the bainitic transformation. The nanostructure was composed of bainitic ferrite plates of nanometric thickness separated by thin layers of retained austenite. It was revealed, that the annealing at the temperature higher than temperature of austempering led to formation of cementite precipitations. At the initial stage of annealing cementite precipitations occurred in the interfaces between ferritic bainite and austenite. With increasing temperature of annealing, the volume fraction and size of cementite precipitations also increased. Simultaneously fine spherical Fe7C3carbides appeared. At the highest annealing temperature the large, spherical Fe7C3carbides as well as cementite precipitates inside the ferrite grains were observed. Moreover the volume fraction of bainitic ferrite and of freshly formed martensite increased in steel as a result of retained austenite transformation during cooling down to room temperature.

Effect of Tempering Temperature on Microstructure and Properties of Low Carbon High Silicon Alloy Steel Treated by Q-P-T Process

2020 ◽  
Vol 993 ◽  
pp. 592-596
Author(s):  
Jun Hu Wei ◽  
Xu Ran ◽  
Han Ying
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Low Carbon ◽  
Tempering Temperature ◽  
Silicon Alloy ◽  
High Silicon

The mechanical properties and microstructure of low-carbon high-silicon alloy steel were examined under various tempering temperatures using the quenching, partitioning and tempering (Q–P–T) process. The performance changed with the variation in tempering temperature. The results show that the microstructure of low carbon high silicon alloy steel treated by Q-P-T process was mainly ferrite, martensite, carbide-free bainite and film-like retained austenite. This alloys exhibited good mechanical properties at tempering temperature of 300 °C. The product of strength and elongation were 33.7 GPa%. Specifically, the Ultimate tensile strength were 1508 MPa, the yield strength were 1048 MPa, and the elongation were 22.4%. At this temperature of 300 °C, the volume fraction of retained austenite reached 10.4%.

Application of Quenching and Partitioning to Improve Ductility of Ultrahigh Strength Low Alloy Steel

2010 ◽  
Vol 654-656 ◽  
pp. 29-32 ◽  
Author(s):  
Wen Quan Cao ◽  
Cun Yu Wang ◽  
Jie Shi ◽  
Han Dong
Keyword(s):  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
High Strength ◽  
Total Elongation ◽  
Low Alloy Steel ◽  
Quenching And Partitioning ◽  
Multiphase Microstructure ◽  
Ultrahigh Strength

In this study Quenching and Partitioning (Q&P) as proposed by Speer was applied to improve the ductility of C-Mn high strength Low Alloy steel (HSLAs). Microstructural observations revealed a multiphase microstructure including first martensite, fresh martensite and retained austenite in the Q&P processed steel. During tensile process, the austenite volume fraction gradually decreased with strain increasing, suggesting the phase transformation induced plasticity for the Q&P processed steel. Ultrahigh strength about 1300-1800MPa and tensile elongation about 20% were obtained after Q&P processing at specific conditions, which is significant higher than that of ~10% of conventional martensitic steel. The the product of tensile strength to total elongation increased from 25 to 35GPa% with increasing carbon content in studied steel. This improved mechanical properties were related to the ductility contribution from TRIP effects of the retained austenite and strength contribution from the hard martensitic matrix. At last it was turned out that the Q&P process is a promising way to produce ultrahigh strength steel with relative high ductility under tailored heat treatment conditions for different micro-alloyed carbon steel.

Crystallography and Mechanical Properties of Ultrafine TRIP-Aided Multi-Phase Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4351-4356 ◽  
Author(s):  
Masayuki Wakita ◽  
Yoshitaka Adachi ◽  
Yo Tomota
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Large Strain ◽  
High Volume ◽  
Underlying Mechanism ◽  
Carbon Steels ◽  
Diffraction Measurement ◽  
Low Carbon ◽  
Multi Phase

This study aims at examining thermomechanical controlled process to realize ultrafine TRIP-aided multi-phase microstructures in low carbon steels. Heavy deformation at a supercooled austenite region was found to lead the formation of 2 μm ferrite as well as retained austenite with high volume fraction. The morphology of retained austenite was changed from film-like shape to granular shape with lowering finish rolling temperature in austenite field. This ultrafine TRIP-aided multi-phase steel showed good balance of tensile strength with total elongation, ie. 1080MPa and 26.9%. A novel in-situ neutron diffraction measurement demonstrated that the retained granular austenite transformed to martensite at a relatively large strain compared with the retained film austenite. The therein-underlying mechanism of the good mechanical properties was discussed from the view points of the morphological and thermodynamical stabilization of retained austenite.

Influence of pre-strain on thermal stability of non-equilibrium microstructures in a low alloy steel

2013 ◽  
Vol 577 ◽  
pp. S614-S618
Author(s):  
Chao Sun ◽  
Shanwu Yang ◽  
Xian Wang ◽  
Rui Zhang ◽  
Xinlai He
Keyword(s):  
Thermal Stability ◽  
Alloy Steel ◽  
Low Alloy Steel ◽  
Thermal Stability Of ◽  
Non Equilibrium
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