scholarly journals Controlling the Content and Morphology of Phase Constituents in Nanobainitic Steel Containing 0.6%C to Obtain the Required Ratio of Strength to Plasticity

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 658
Author(s):  
Jarosław Marcisz ◽  
Bogdan Garbarz ◽  
Aleksandra Janik ◽  
Władysław Zalecki
Keyword(s):  
Mechanical Properties ◽  
Phase Composition ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Total Elongation ◽  
Isothermal Transformation ◽  
Effect Of Temperature ◽  
Isothermal Heat Treatment ◽  
Dilatometric Studies ◽  
Kinetics Of

The phase composition of nanobainitic steel 0.56–0.60%C, 1.68–1.95%Mn, 1.58–1.80%Si, 1.30–1.47%Cr, 0.57–0.75%Mo is described in this paper. The phase composition is controlled in order to obtain diversified mechanical properties for specific applications, such as armor plates. The effect of temperature and time of isothermal heat treatment on both the microstructure and the mechanical properties of the steel were determined. Dilatometric studies, as well as measurements of volume fraction and size distribution of retained austenite were carried out. Analysis of the kinetics of isothermal transformation in the temperature range of 200–225 °C for times of up to 144 h were also carried out, and the parameters of the production process of the steel were determined. A microstructure consisting of nanolathy carbideless bainite and blocky and lathy retained austenite, providing tensile strength of at least 2000 MPa, yield strength of at least 1300 MPa, and total elongation of at least 10% has been found.

Isothermal Transformation, Microstructure and Mechanical Properties of Ausformed Low-Carbon Carbide-Free Bainitic Steel

2018 ◽  
Vol 941 ◽  
pp. 329-333 ◽  
Author(s):  
Jiang Ying Meng ◽  
Lei Jie Zhao ◽  
Fan Huang ◽  
Fu Cheng Zhang ◽  
Li He Qian
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
Isothermal Transformation ◽  
Bainitic Transformation ◽  
Isothermal Treatment ◽  
Bainitic Steel ◽  
Low Carbon ◽  
Microstructure And Mechanical Properties

In the present study, the effects of ausforming on the bainitic transformation, microstructure and mechanical properties of a low-carbon rich-silicon carbide-free bainitic steel have been investigated. Results show that prior ausforming shortens both the incubation period and finishing time of bainitic transformation during isothermal treatment at a temperature slightly above the Mspoint. The thicknesses of bainitic ferrite laths are reduced appreciably by ausforming; however, ausforming increases the amount of large blocks of retained austenite/martenisite and decreases the volume fraction of retained austenite. And accordingly, ausforming gives rise to significant increases in both yield and tensile strengths, but causes noticeable decreases in ductility and impact toughness.

Study on Microstructures and Mechanical Properties of Cold-Rolled C-Mn-Si-Al TRIP Steel

2010 ◽  
Vol 146-147 ◽  
pp. 678-681
Author(s):  
Zheng You Tang ◽  
Hua Ding
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Total Elongation ◽  
Partial Substitution ◽  
Cold Rolled ◽  
Microstructures And Mechanical Properties

The effect of the partial substitution of Si by Al on the microstructures and the mechanical properties of cold rolled C-Mn-Si TRIP steel was investigated. The results show that the partial substitution of Si by Al could refine the microstructures, increase the volume fraction of ferrite and retained austenite. In addition, the excellent mechanical properties of the Al partial substituted TRIP steel could be obtained, the tensile strength, total elongation and strength-ductility of C-Mn-Si-Al TRIP steel are 739MPa, 38% and 28082MPa%, respectively.

Microstructure and Mechanical Properties of TRIP-Aided Steels with Different Heat Treatments

2015 ◽  
Vol 817 ◽  
pp. 439-443 ◽  
Author(s):  
Rui Dong ◽  
Ai Min Zhao ◽  
Ran Ding ◽  
Jian Guo He ◽  
Han Jiang Hu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Total Elongation ◽  
Heat Treatments ◽  
Second Phase ◽  
Soft Matrix ◽  
Significant Difference

The microstructures, mechanical properties and retained austenite characteristics of TRIP-aided steels with three different heat treatments were studied in this paper. The results indicated that the designed annealing treatments resulted in completely different matrices and the morphologies of second phase, and a significant difference in mechanical properties. The TAM steel was found to have fine annealed martensite lath matrix and inter lath acicular retained austenite, and possessed an excellent combination of strength and elongation which attributed to the highest retained austenite volume fraction and carbon concentration. For TPF steel, the higher instability and lower carbon content of retained austenite and the soft matrix resulted in the lowest ultimate tensile strength and total elongation. While in TBF steel, the stability of retained austenite was lower than that in TAM steel but higher than that in TPF steel. The ultimate tensile strength of TBF was significantly higher than the TAM and TPF steels, but the ductility of TBF steel was lower than TAM steel.

scholarly journals The Effects of Micro-Segregation on Isothermal Transformed Nano Bainitic Microstructure and Mechanical Properties in Laser Cladded Coatings

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3017
Author(s):  
Yanbing Guo ◽  
Zhuguo Li ◽  
Liqun Li ◽  
Kai Feng
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Isothermal Heat Treatment ◽  
Isothermal Temperature ◽  
Bainitic Microstructure ◽  
Microstructure Morphology ◽  
Tunable Mechanical Properties ◽  
The Stability

The design of metastable retained austenite is the key issue to obtain nano bainitic steel with high strength and toughness. In this study, nanostructured Fe-based bainitic coatings were fabricated using laser cladding and following isothermal heat treatment. The microstructures and mechanical properties of the laser cladded coating were investigated. The results show that the Mn, Cr, Co, and Al segregated at the solidified prior grain boundaries. The micro-segregation of the solutes strongly influenced the stability of the austenite. As the isothermal temperature decreases, the interface of the bainite and blocky retained austenite approach to the prior interdendritic regions with the decreasing isothermal temperature, and the final volume fraction also decreases. The volume fractions of each phase and microstructure morphology of the coatings were determined by the interdendritic micro-segregation and isothermal temperatures. The stability of the blocky retained austenite distributed at the interdendritic area was lower than that of film and island-like morphology. This phenomenon contributed to the ductile and tough nano bainitic coatings with tunable mechanical properties.

scholarly journals Effect of Pre-Quenching Process on Microstructure and Mechanical Properties in a Nb-Microalloyed Low Carbon Q-P Steel

2015 ◽  
Vol 816 ◽  
pp. 729-735 ◽  
Author(s):  
Jun Zhang ◽  
Hua Ding ◽  
Jing Wei Zhao
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Room Temperature ◽  
Volume Fraction ◽  
Total Elongation ◽  
Trip Effect ◽  
Low Carbon ◽  
Quenching And Partitioning ◽  
The Stability ◽  
Critical Annealing

A refined microstructure consisting of martensite and retained austenite at room temperature has been produced in a Nb-microalloyed low carbon Si-Mn steel by a novel heat-treatment, pre-quenching prior to quenching and partitioning processes (Q&Q-P). The results showed that compared with the conventional quenching and partitioning steel the mechanical properties of steel obtained by the novel treatment have been significantly improved, with a good combination of ultimate tensile strength (1000MPa) and total elongation (above 30%). Meanwhile, the volume fraction of retained austenite has been increased. It was found that the improvement of mechanical properties was mainly attributed to the enhanced TRIP effect due to the relatively high fraction of metastable retained austenite at room temperature. The increased stability of austenite results from the C and Mn partitioning during inter-critical annealing, which increased the chemical stability of austenite. The formation of refined austenite at inter-critical annealing also had a positive effect on the stability of the austenite. As a consequence, the volume fraction of retained austenite at room temperature was significantly increased. Compared with the Q-P steel, the Q&Q-P steel exhibited higher work hardening exponents during the stage of TRIP effect and had the higher ductility.

scholarly journals The Impact of Retained Austenite on the Mechanical Properties of Bainitic and Dual Phase Steels

2022 ◽  
Author(s):  
Bogusława Adamczyk-Cieślak ◽  
Milena Koralnik ◽  
Roman Kuziak ◽  
Kamil Majchrowicz ◽  
Tomasz Zygmunt ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Transformation Temperature ◽  
Retained Austenite ◽  
Tensile Tests ◽  
Total Elongation ◽  
Isothermal Transformation ◽  
Bainitic Transformation ◽  
Bainitic Steel ◽  
Continuous Cooling

AbstractThis paper presents the microstructural changes and mechanical properties of carbide-free bainitic steel subjected to various heat treatment processes and compares these results with similarly treated ferritic–pearlitic steel. A key feature of the investigated steel, which is common among others described in the literature, is that the Si content in the developed steel was >1 wt.% to avoid carbide precipitation in the retained austenite during the bainitic transformation. The phase identification before and after various heat treatment conditions was carried out based on microstructural observations and x-ray diffraction. Hardness measurements and tensile tests were conducted to determine the mechanical properties of the investigated materials. In addition, following the tensile tests, the fracture surfaces of both types of steels were analyzed. Changing the bainitic transformation temperature generated distinct volume fractions of retained austenite and different values of mechanical strength properties. The mechanical properties of the examined steels were strongly influenced by the volume fractions and morphological features of the microstructural constituents. It is worth noting that the bainitic steel was characterized by a high ultimate tensile strength (1250 MPa) combined with a total elongation of 18% after austenitizing and continuous cooling. The chemical composition of the bainitic steel was designed to obtain the optimal microstructure and mechanical properties after hot deformation followed by natural cooling in still air. Extensive tests using isothermal transformation to bainite were conducted to understand the relationships between transformation temperature and the resulting microstructures, mechanical properties, and fracture characteristics. The isothermal transformation tests indicated that the optimal relationship between the sample strength and total elongation was obtained after bainitic treatment at 400 °C. However, it should be noted that the mechanical properties and total elongation of the bainitic steel after continuous cooling differed little from the condition after isothermal transformation at 400 °C.

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

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1090 ◽  
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.

Influence of the Austempering Temperature on the Microstructure and Crystallography of a Carbide-Free Bainitic Steel

2011 ◽  
Vol 172-174 ◽  
pp. 797-802 ◽  
Author(s):  
Jean Christophe Hell ◽  
Moukrane Dehmas ◽  
Guillaume Geandier ◽  
Nathalie Gey ◽  
Sebastien Allain ◽  
...  
Keyword(s):  
Retained Austenite ◽  
Volume Fraction ◽  
Bainitic Ferrite ◽  
High Energy ◽  
Isothermal Transformation ◽  
Bainitic Transformation ◽  
Bainitic Steels ◽  
Austempering Temperature ◽  
Kinetics Of

We elaborated two carbide-free bainitic steels with different microstructures through specific heat treatments and alloy design. EBSD analysis was used to point out major differences in these microstructures. In-situ characterizations of the bainitic transformation were performed by high energy synchrotron diffraction to go further into the study of each phase characteristics. The elaborated microstructures exhibited various phase fractions of bainitic ferrite, retained austenite and blocks of martensite and retained austenite. Moreover, the volume fraction of retained austenite increased with higher austempering temperatures. On the other hand, the austempering temperatures showed a strong influence on the kinetics of the bainitic transformation. Isothermal transformation under Ms showed a two stage transformation which led first to the formation of self-tempered martensite and then to bainitic ferrite. Furthermore, the evolution of the austenitic cell parameter showed enrichment in carbon ruled by diffusional mechanisms.

Effect of Si Content on Microstructure and Properties of 60Si2CrVA Spring Steel

2014 ◽  
Vol 968 ◽  
pp. 63-66 ◽  
Author(s):  
Fei Zhao ◽  
Zhan Ling Zhang ◽  
Jun Shuai Li ◽  
Cui Ye ◽  
Ni Li
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Testing Machine ◽  
Spring Steel ◽  
Impact Testing ◽  
X Ray ◽  
Comprehensive Properties ◽  
Spring Steels ◽  
Si Content

The microstructure and mechanical properties of the four spring steels with different Si content treated by Q-I-Q-T process were studied by metallographic microscope, MTS, impact testing machine and X-ray stress analyzer. The results show that the tensile strength and yield strength is first increased and then decreased with the increase of Si content, the volume fraction of retained austenite and elongation are fist decreased and then increased when the Si content is less than 2.1%, and the microstructure become finer and homogeneous. When Si content reaches 2.1%, the comprehensive properties of 60Si2CrVA spring steel is the best.

Microstructure and Mechanical Properties of a Low-Carbon Steel Treated by One-Step Quenching and Partitioning Process

2014 ◽  
Vol 1082 ◽  
pp. 202-207 ◽  
Author(s):  
Shu Yan ◽  
Xiang Hua Liu
Keyword(s):  
Mechanical Properties ◽  
Carbon Steel ◽  
Microstructural Evolution ◽  
Retained Austenite ◽  
Uniform Elongation ◽  
Low Carbon Steel ◽  
Total Elongation ◽  
Low Carbon ◽  
Quenching And Partitioning ◽  
Partitioning Time

A low carbon steel was treated by quenching and partitioning (Q&P) process, and a detailed characterization of the microstructural evolution and testing of mechanical properties were carried out. The resulted mechanical properties indicate that with the partitioning time increasing, the tensile strength decreases rapidly first and then remains stable, and the total elongation increases first then decreases. The investigated steel subjected to Q&P process exhibits excellent products of strength and elongation (17.8-20.6 GPa•%). The microstructural evolution of martensite matrix during the partitioning step was observed, and the morphology and content of retained austenite were characterized. The working hardening behavior of the samples was analyzed, and the retained austenite with higher carbon content contributes to the uniform elongation more effectively.

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