Mechanical Properties and Microstructural Aspects of Two High-Manganese Steels with TWIP/TRIP Effects: A Comparative Study

This article is focused on the mechanical behavior and its relationship with the microstructural changes observed in two high-manganese steels presenting twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP), namely Steel B and Steel C, respectively. Chemical compositions were similar in manganese, but carbon content of Steel B approximately doubles Steel C, which directly impacted on the stacking fault energy (SFE), microstructure and mechanical response of each alloy. Characterization of as-cast condition by optical microscope revealed a fully austenitic microstructure in Steel B and a mixed microstructure in Steel C consisting of austenite grains and thermal-induced (εt) martensite platelets. Same phases were observed after the thermo-mechanical treatment and tensile tests, corroborated by means of X-Ray Diffraction (XRD), which confirms no phase transformation in Steel B and TRIP effect in Steel C, due to the strain-induced γFCC→εHCP transformation that results in an increase in the ε-martensite volume fraction. Higher values of ultimate tensile strength, yield stress, ductility and impact toughness were obtained for Steel B. Significant microstructural changes were revealed in tensile specimens as a consequence of the operating hardening mechanisms. Scanning Electron Microscopy (SEM) observations on the tensile and impact test specimens showed differences in fracture micro-mechanisms.

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Computer-Aided Material Design for Crash Boxes Made of High Manganese Steels

Metals ◽

10.3390/met9070772 ◽

2019 ◽

Vol 9 (7) ◽

pp. 772 ◽

Cited By ~ 1

Author(s):

Angela Quadfasel ◽

Marco Teller ◽

Manjunatha Madivala ◽

Christian Haase ◽

Franz Roters ◽

...

Keyword(s):

Sheet Thickness ◽

Material Design ◽

Tensile Tests ◽

Material Strength ◽

High Manganese ◽

Material Efficiency ◽

Material Condition ◽

High Manganese Steels ◽

Material Conditions ◽

Manganese Steels

During the last decades, high manganese steels (HMnS) were considered as promising materials for crash-relevant automobile components due to their extraordinary energy absorption capability in tensile tests. However, in the case of a crash, the specific energy, absorbed by folding of a crash box, is lower for HMnS as compared to the dual phase steel DP800. This behavior is related to the fact that the crash box hardly takes advantage of the high plastic formability of a recrystallized HMnS during deformation. It was revealed that with the help of an alternative heat treatment after cold rolling, the strength of HMnS could be increased for low strains to achieve a crash behavior comparable to DP800. In this work, a multi-scale finite element simulation approach was used to analyze the crash behavior of different material conditions of an HMnS. The crash behavior was evaluated under consideration of material efficiency and passenger safety criteria to identify the ideal material condition and sheet thickness for crash absorption by folding. The proposed simulation methodology reduces the experimental time and effort for crash box design. As a result of increasing material strength, the simulation exhibits a possible weight reduction of the crash box, due to thickness reduction, up to 35%.

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Deformation Behavior and Microstructure of Low Carbon High Manganese Steels in Tensile Strain

Materials Science Forum ◽

10.4028/www.scientific.net/msf.620-622.335 ◽

2009 ◽

Vol 620-622 ◽

pp. 335-338

Author(s):

Lu Lu Wang ◽

Guang Xin Li ◽

Xin Pei Ma ◽

Feng Jiang ◽

Jun Sun

Keyword(s):

Phase Transformation ◽

Manganese Content ◽

Tensile Tests ◽

Strain Hardening Exponent ◽

Low Carbon ◽

High Manganese ◽

Deformation Phase ◽

Before And After ◽

High Manganese Steels ◽

Manganese Steels

The mechanical properties of two high manganese steels with manganese contents (15% and 25%) were investigated during tensile tests at room temperature. The results indicated that the strengths of steels were a little low and the elongations were improved greatly with increasing the manganese content. Stress fluctuations were found during tensile tests of the Fe-15Mn steels, and as the strain increased the range of stress fluctuations became wider. The strain hardening exponent n of samples changed with strain in a parabola model. The microstructures before and after deformation were investigated and the results showed that phase transformation of γ (fcc) →ε (hcp) and γ (fcc) →ε (hcp) →α (bcc) induced plasticity occurred in the Fe-15Mn steels. However, in the Fe-25Mn steels, at the beginning stage of the deformation, phase transformation induced plasticity played an important role, and with the increase of deformation, the main mechanism was twinning induced plasticity.

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