scholarly journals Microstructure and Mechanical Properties of a Medium-Mn Steel with 1.3 GPa-Strength and 40%-Ductility

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2233
Author(s):  
Shaobin Bai ◽  
Wentao Xiao ◽  
Weiqiang Niu ◽  
Dazhao Li ◽  
Wei Liang
Keyword(s):  
Mechanical Properties ◽  
Tensile Elongation ◽  
High Strength ◽  
High Volume ◽  
Equal Mass ◽  
Medium Mn Steel ◽  
Mass Fractions ◽  
Superior Mechanical Properties ◽  
Microalloying Elements ◽  
Mn Steel

Steel designs with superior mechanical properties have been urgently needed in automotive industries to achieve energy conservation, increase safety, and decrease weight. In this study, the aging process is employed to enhance the yield strength (YS) by tailoring the distribution of V-rich precipitates and to improve ductility by producing high volume fractions of recrystallized ferrite in cold-rolled medium-Mn steel. A reliable method to acquire ultra-high strength (1.0–1.5 GPa), together with ductility (>40%), is proposed via utilizing non-recrystallized austenite and recrystallized ferrite. Similarly to conventional medium-Mn steels, the TRIP effect, along with the mild TWIP effect, is responsible for the main deformation mechanisms during tensile testing. However, the coupled influence of precipitation strengthening, grain refinement strengthening, and dislocation strengthening contributes to an increase in YS. The studied steel, aged at 650 °C for 5 h, demonstrates a YS of 1078 MPa, ultimate tensile strength (UTS) of 1438 MPa, and tensile elongation (TE) of 30%. The studied steel aged at 650 °C for 10 h shows a UTS of 1306 MPa and TE of 42%, resulting in the best product in terms of of UTS and TE, at 55 GPa·%. Such a value surpasses that of the previously reported medium-Mn steels containing equal mass fractions of various microalloying elements.

A novel medium-Mn steel with superior mechanical properties and marginal oxidization after press hardening

2021 ◽  
Vol 205 ◽  
pp. 116567
Author(s):  
Shuoshuo Li ◽  
Pengyu Wen ◽  
Shilei Li ◽  
Wenwen Song ◽  
Yandong Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Press Hardening ◽  
Medium Mn Steel ◽  
Superior Mechanical Properties ◽  
Mn Steel

scholarly journals Microstructure and Local Mechanical Properties of the Heat-Affected Zone of a Resistance Spot Welded Medium-Mn Steel

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3362
Author(s):  
Manfred Stadler ◽  
Ronald Schnitzer ◽  
Martin Gruber ◽  
Katharina Steineder ◽  
Christina Hofer
Keyword(s):  
Mechanical Properties ◽  
Heat Affected Zone ◽  
Great Influence ◽  
High Strength ◽  
Total Elongation ◽  
Resistance Spot ◽  
Heat Treated ◽  
Medium Mn Steel ◽  
Mn Steel ◽  
Spot Welded

The properties of the heat-affected zone (HAZ) are reported to have a great influence on the mechanical performance of resistance spot welded advanced high strength steels. Therefore, in the present work, the HAZ of a medium-Mn steel is characterized regarding its microstructure and its mechanical properties depending on the distance to the fusion zone (FZ). In order to obtain the local mechanical properties of the HAZ, samples were heat-treated in a joule-heating thermal simulator using different peak temperatures to physically simulate the microstructure of the HAZ. By comparing the microstructure and the hardness of these heat-treated samples and the HAZ, the local peak temperatures within the HAZ could be determined. Subsequently, tensile tests were conducted, and the austenite phase fraction was measured magnetically on the physically simulated HAZ samples in order to determine the local mechanical properties of the HAZ. As verified by energy-dispersive X-ray spectroscopy, peak temperatures above 1200 °C led to a uniform distribution of manganese, resulting in a predominantly martensitic microstructure with high strength and low total elongation after quenching. Below 1100 °C, the diffusion of manganese is restricted, and considerable fractions of austenite remain stable. The austenite fraction increases almost linearly with decreasing peak temperature, which leads to an increase of the total elongation and to a slight decrease in the strength, depending on the distance to the FZ. Temperatures below 700 °C exhibit hardly any effect on the initial microstructure and mechanical properties.

scholarly journals Effects of Servo Tensile Test Parameters on Mechanical Properties of Medium-Mn Steel

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3793
Author(s):  
Xuemin Chi ◽  
Shuo Han
Keyword(s):  
Neural Network ◽  
Mechanical Properties ◽  
Back Propagation ◽  
High Strength ◽  
Total Elongation ◽  
Back Propagation Neural Network ◽  
Analytical Models ◽  
Medium Mn Steel ◽  
Supplemental Experiment ◽  
Mn Steel

As a new type of third-generation automotive steel with high strength and plasticity, medium-Mn steel (MMnS) has been widely used in automotive industries for its excellent properties. In recent years, servo stamping technology for high-strength metal forming is a hot topic due to its good performance in forming under complex processing conditions, and servo parameters determine the forming quality. In this paper, experiments considering tensile speed and position where speed changes (PSC) were carried out on MMnS to investigate the influences of tensile parameters on mechanical properties including strength and total elongation (TE). The results show that PSC does not significantly impact total elongation. Initial tensile speed (ITS) and final tensile speed (FTS) significantly impact the total elongation. The interaction between all tensile parameters can impact total elongation. Two artificial neural networks, back propagation neural network (BPNN) and radial basis function neural network (RBFNN), were used to establish analytical models. The results of supplemental experiment and residual analysis were conducted to verify the accuracy of the analytical models. The BPNN has a better performance and the analytical model shows that with the increase of PSC, it has a slight impact on the changes of optimal and minimum total elongation, but the combinations of tensile parameters to obtain total elongations higher than 40% change significantly.

Mechanical Properties and Aging Behavior of Ultrafine Grained Al-Ag Alloy Fabricated by Accumulative Roll-Bonding

2014 ◽  
Vol 794-796 ◽  
pp. 851-856
Author(s):  
Tadashiege Nagae ◽  
Nobuhiro Tsuji ◽  
Daisuke Terada
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Accumulative Roll Bonding ◽  
Precipitation Hardening ◽  
Tensile Elongation ◽  
Solution Treatment ◽  
High Strength ◽  
Subsequent Aging ◽  
Roll Bonding ◽  
Ultrafine Grained

Accumulative roll-bonding (ARB) process is one of the severe plastic deformation processes for fabricating ultrafine grained materials that exhibit high strength. In aluminum alloys, aging heat treatment has been an important process for hardening materials. In order to achieve good mechanical properties through the combination of grain refinement hardening and precipitation hardening, an Al-4.2wt%Ag binary alloy was used in the present study. After a solution treatment at 550°C for 1.5hr, the alloy was severely deformed by the ARB process at room temperature (RT) up to 6 cycles (equivalent strain of 4.8). The specimens ARB-processed by various cycles (various strains) were subsequently aged at 100, 150, 200, 250°C, and RT. The hardness of the solution treated (ST) specimen increased by aging. On the other hand, hardness of the ARB processed specimen decreased after aging at high temperatures such as 250°C. This was probably due to coarsening of precipitates or/and matrix grains. The specimen aged at lower temperature showed higher hardness. The maximum harnesses achieved by aging for the ST specimen, the specimens ARB processed by 2 cycles, 4 cycles and 6 cycles were 55HV, 71HV, 69HV and 65HV, respectively. By tensile tests it was shown that the strength increased by the ARB process though the elongation decreased significantly. However, it was found that the tensile elongation of the ARB processed specimens was improved by aging without sacrificing the strength. The results suggest that the Al-Ag alloy having large elongation as well as high strength can be realized by the combination of the ARB process for grain refinement and the subsequent aging for precipitation hardening.

Exploitation Load Impact on Electrochemical Properties of Shipbuilding 7xxx Series Aluminum Alloy Joints Prepared with TIG and FSW Methods

2015 ◽  
Vol 236 ◽  
pp. 53-61
Author(s):  
Wojciech Jurczak
Keyword(s):  
Mechanical Properties ◽  
Corrosion Potential ◽  
Tensile Load ◽  
Electrochemical Corrosion ◽  
High Strength ◽  
Shipbuilding Industry ◽  
Friction Stir ◽  
Superior Mechanical Properties ◽  
Series Aluminum Alloy ◽  
Joint Quality

The paper presents the results of investigations on mechanical properties and electrochemical potential distribution within arc welded (TIG) and friction stir welded (FSW) joints subjected to slow strain rate tests. The materials investigated were high-strength 7xxx series (7020 and its modification 7020M) aluminum alloys intended for shipbuilding. The objectives were joint quality assessment and comparison of the advantages of new FSW method with the traditional TIG methods commonly utilized in shipbuilding industry. Joint quality was evaluated based on mechanical investigations, hardness distribution tests and simultaneous electrochemical corrosion potential measurements at various locations within the welded joints.Initiation of corrosion processes on TIG and FSW joints was identified as a radical decrease in corrosion potential related to load followed by oxide layer cracking. Arc welded (TIG) joints of 7xxx series alloys undergo corrosion at lower values of tensile load applied as compared to the FSW joints. Superior mechanical properties and higher corrosion resistance of the FSW joints make this technology well-suited for joining high-strength 7xxx series alloys.

Microstructure and mechanical properties of a novel medium Mn steel with Cr and Mo microalloying

2021 ◽  
Vol 825 ◽  
pp. 141926
Author(s):  
Chao Wang ◽  
Liming Yu ◽  
Ran Ding ◽  
Yongchang Liu ◽  
Huijun Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Microstructure And Mechanical Properties ◽  
Medium Mn Steel ◽  
Mn Steel

Investigation on Microstructure and Martensitic Transformation Mechanism for the Warm-Stamped Third-Generation Automotive Medium-Mn Steel

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Xiaodong Li ◽  
Ying Chang ◽  
Cunyu Wang ◽  
Shuo Han ◽  
Daxin Ren ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Strain Rate ◽  
Compressive Load ◽  
High Strength ◽  
Third Generation ◽  
Transformation Mechanism ◽  
Loading Method ◽  
Strain And Strain Rate ◽  
Medium Mn Steel ◽  
Mn Steel

With the development of the automotive industry, the application of the high-strength steel (HSS) becomes an effective way to improve the lightweight and safety. In this paper, the third-generation automotive medium-Mn steel (TAMM steel) is studied. The warm-stamped TAMM steel holds the complete and fine-grained martensitic microstructure without decarbonization layer, which contributes to high and well-balanced mechanical properties. Furthermore, the martensitic transformation mechanism of the TAMM steel is investigated by the dilatation tests. The results indicate that the effects of the loading method on the Ms temperature under different loads are different. The Ms temperature is hardly influenced under the tensile loads and low compressive load. However, it is slightly decreased under the high compressive load. Moreover, the effects of the strain and strain rate on the Ms temperature are insignificant and can be neglected. As a result, this research proves that the martensitic transformation of the TAMM steel is rarely influenced by the process parameters, such as stamping temperature, loading method, load, strain, and strain rate. The actual stamping process can be designed and controlled accurately referring to the continuous cooling transformation (CCT) curves to realize the required properties and improve the formability of the automotive part.

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