The Mechanical and Deformation Behavior of TWIP Steel Prepared by Directional Solidification

2014 ◽  
Vol 783-786 ◽  
pp. 761-765 ◽  
Author(s):  
Dan Wang ◽  
Kun Wang ◽  
Zi Mu Shi ◽  
Fu Sheng Han
Keyword(s):  
Mechanical Properties ◽  
Strain Hardening ◽  
Twip Steel ◽  
True Strain ◽  
Longitudinal Direction ◽  
True Stress ◽  
Grain Structure ◽  
Directionally Solidified ◽  
Twip Steels ◽  
Columnar Grain

A directionally solidified TWIP steel (Fe-25Mn-2.5Al-2.5Si) was prepared by liquid metal cooling technology. The microstructure and mechanical behavior were examined and compared with usually solidified samples. The directionally solidified TWIP steel shows a typical columnar grain structure, and the maximum true stress and true strain along the longitudinal direction of the sample are 1060MPa and 71% respectively. As a comparison, the usually solidified samples shows an equiaxed grain microstructure with the maximum true stress and true strain of only 994MPa and 58%, respectively. Moreover, the two solidification modes also lead to very different strain hardening behavior, particularly in the changes of strain hardening rate with strain. This suggests that the grain boundary plays a key role in the mechanical properties of TWIP steels, and changing the grain boundaries can be effective to improve the comprehensive mechanical properties of TWIP steels.

Determination of Critical Stress for Dynamic Recrystallization of a High-Mn Austenitic TWIP Steel Micro-Alloyed with Vanadium

2016 ◽  
Vol 1812 ◽  
pp. 41-46
Author(s):  
Elvira García-Mora ◽  
Ignacio Mejía ◽  
Francisco Reyes-Calderón ◽  
José M. Cabrera
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Strain Hardening ◽  
Critical Stress ◽  
Twip Steel ◽  
True Strain ◽  
Compression Tests ◽  
Hollomon Parameter ◽  
Strain And Strain Rate ◽  
Twip Steels

ABSTRACTWhen high strength and high ductility are required, the Twinning Induced Plasticity steels are an excellent choice. Their mechanical advantages are perfectly known in the automotive industry. Then, they are currently deeply studied. During the deformation at high temperature, TWIP steel experiences dynamic recrystallization. This mechanism results from dislocation interactions, and it depends of temperature, stress, strain, and strain rate. Experimental data give the maximum stress reached by the material, but the critical stress which determinates the DRX onset must be calculated from the strain hardening rate. Both stress and strain change simultaneously, and this variation gives the analytic data to determine σc, which is located at the inflection point of θ-σ plot. The main purpose of this paper was to study how the chemical composition and the experimental parameters (temperature and strain rate) affect the DRX, by the calculation and analysis of the σc values. Hot compression tests were applied to a pair of TWIP steels to compare the DRX onset and its relationship with the vanadium addition. The experimental variables were temperature and strain rate. The true stress–true strain plots were used to calculate σc by cutting data up to a previous point before the σp value, then, a polynomial fit and derivation were applied. The Zener-Hollomon parameter (Z) versus the stresses (peak and critical) plots show how the micro-alloying element vanadium improves the strain hardening in the analyzed TWIP steels.

Magnetic and Mechanical Properties of Directionally Solidified Fe-6.5wt.%Si Alloy

2011 ◽  
Vol 687 ◽  
pp. 122-128
Author(s):  
Y. S. Deng ◽  
Xian Shi Fang ◽  
Feng Ye ◽  
Y. Qiao ◽  
Jun Pin Lin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Directional Solidification ◽  
Grain Growth ◽  
Magnetic Induction ◽  
Crystal Orientation ◽  
Grain Structure ◽  
Directionally Solidified ◽  
Columnar Grains ◽  
Columnar Grain ◽  
Saturation Magnetic Induction

Directional solidification technique was employed to produce Fe-6.5wt.%Si alloy with coarse columnar-grain structure, which was almost single crystal. The sectional diameters of columnar grains range from 2.2 to 6.8 mm. The saturation magnetic induction was 2.39 T. In this work, grain growth started from either a Fe-6.5wt.%Si crystal which was not melted at bottom of the specimen or a freely nucleated Fe-6.5wt.%Si crystal as the specimen was completely melted. It was found that the starting situation of the directional solidification plays an important role in the crystal orientation, and hence in properties.

The effect of substrate bias on the characteristics of CrN coatings deposited by DC-superimposed HiPIMS system

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744032 ◽  
Author(s):  
X. Zuo ◽  
F. Xia ◽  
D. Zhang ◽  
P. L. Ke ◽  
Q. M. Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bias Voltage ◽  
Indentation Test ◽  
Grain Structure ◽  
Substrate Bias ◽  
Cross Sectional ◽  
Microstructure And Mechanical Properties ◽  
Columnar Grain ◽  
Influence Of Substrate ◽  
Crn Coatings

Chromium nitride coatings were prepared by reactive DC-superimposed high-power-impulse magnetron sputtering (HiPIMS) system. The influence of substrate bias on the microstructure and mechanical properties of CrN coatings was investigated. XRD and cross-sectional SEM were utilized to characterize the film structures. Mechanical properties were characterized by nanoindentation and Vickers indentation test. The results revealed that the microstructure and mechanical properties of CrN coatings were affected by bias voltage. The CrN coatings exhibited dense and fine columnar grain structure with the hardness of about 18.7 GPa. The fracture toughness of CrN coatings was around 3.16 MPa ⋅ m[Formula: see text]. However, further increase of the bias voltage from −250 V to −300 V led to the degradation of coating properties.

Influence of Grain Size on Mechanical Properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP Steel

2011 ◽  
Vol 197-198 ◽  
pp. 655-661
Author(s):  
Ze Bin Yang ◽  
Ding Yi Zhu ◽  
Wei Fa Yi ◽  
Shu Mei Lin ◽  
Cheng Mei Du
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Strain Hardening ◽  
Twip Steel ◽  
Optical Microscope ◽  
Coarse Grained ◽  
Microstructure Observation ◽  
Transmission Electron ◽  
Average Grain Size

We investigate the influence of grain size on mechanical properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP steel by unidirectional tensile. Meanwhile the microstructures of the TWIP steel were observed and analyzed by optical microscope (OM) and transmission electron microscope (TEM). The experimental results show that the TWIP steel’s yield strength and tensile strength decrease with the increasing of grain size, whereas the plasticity increases with it. When the average grain size reaches to 27μm, the tensile strength is 1080MPa, the elongation percentage is 77%, and the strength-plasticity product achieves the 83160MPa•%. Steel’s strain hardening rate can be changed from three-stage to four-stage with the increasing of grain sizes, the areas of strain hardening by twin deformation mechanism are expanded. Through the microstructure observation we found that, coarse-grained TWIP steel conducts to twinning formation, the high density twins can increase the alloy’s ductility by splitting the grain.

Effect of Strain Rate on the Microstructures and Properties of Hot–Rolled TWIP Steel in the Solution Condition

2012 ◽  
Vol 430-432 ◽  
pp. 256-259 ◽  
Author(s):  
Yang Yang ◽  
Chun Fu Li ◽  
Kai Hong Song
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Twip Steel ◽  
Tensile Tests ◽  
Strain Rate Range ◽  
Strain Hardening Exponent ◽  
Solution Condition ◽  
Twip Steels ◽  
Hot Rolled ◽  
Strain Hardening Behavior

TWIP steel containing 0.21% C, 24.4% Mn, 0.9% Si, 1.84% Al, 4.61% Cr, 1.89% Ni, 0.41% Mo and 0.012% Nb was investigated. Tensile tests of this steel were performed in the strain rate range of 10−4–10−3 s−1. Results indicate that tensile properties of TWIP steel at room temperature are sensitive to strain rate in the studied range. Analyses on the relationship between strain–hardening exponent and strain rates show that the formation of twins during deformation greatly affects the strain–hardening behavior of TWIP steels.

Strain-Hardening Characteristics of Ti-6Al-2Sn-4Zr-2Mo Alloy

1975 ◽  
Vol 97 (4) ◽  
pp. 382-383 ◽  
Author(s):  
Amiya K. Chakrabarti ◽  
James A. Roberson ◽  
William R. Kerr
Keyword(s):  
Grain Size ◽  
Plastic Strain ◽  
Strain Hardening ◽  
Power Law ◽  
True Strain ◽  
True Stress ◽  
Strain Hardening Exponent ◽  
Strain Relation

The strain-hardening exponent (n) is considered to be numerically equal to the uniform plastic strain for materials which exhibit a power low true stress true strain relation. In Ti-6Al-2Sn-4Zr-2Mo alloy a considerable deviation between the uniform plastic strain and the strain hardening exponent has been observed irrespective of the variations in microstructures and grain size. The present investigation indicates that a power law true stress true strain relation of the type σ = Kεn may not be valid for this material.

Ultrafine-Grained Structure and Mechanical Properties of a High-Mn Twinning Induced Plasticity Steel

2016 ◽  
Vol 838-839 ◽  
pp. 392-397 ◽  
Author(s):  
Pavel Kusakin ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev ◽  
Dmitri Molodov
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Cold Rolling ◽  
Twip Steel ◽  
True Strain ◽  
Total Elongation ◽  
Recrystallization Annealing

The influence of thermo-mechanical treatment consisting of cold rolling followed by recrystallization annealing on the grain size and mechanical properties of a high-Mn TWIP steel was studied. An Fe-23Mn-0.3C-1.5Al TWIP steel (wt. %) was subjected to extensive cold rolling with a reduction of 80% (true strain of ∼1.6) and then annealed in the temperature interval ranging from 400 to 900 °C during 20 minutes. Recovery processes took place below 500 °C, partial recrystallization was evident at ~550°C and fully recrystallized structure evolved after annealing at 600 °C and higher. The static recovery resulted in a slight decrease in the yield strength from 1400 MPa to 1250 MPa and the ultimate tensile strength from 1540 MPa to 1400 MPa whereas the total elongation of 4% did not changed. The recrystallization development led to a drastic drop of strength and an increase in ductility. The yield strength of 225 MPa, the ultimate tensile strength of 700 MPa and the total elongation of 79% was obtained after annealing at 900 °C. Correspondingly, the grain size increased from 0.2 μm to 6.2 μm with increase in anneal temperature from 550 to 900°C.

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