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Li L.,The State Key Laboratory of Refractories and Metallurgy | Li L.,Wuhan University of Science and Technology | Ye B.,Wuhan University of Science and Technology | Liu S.,Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education | And 4 more authors.
Journal of Materials Engineering and Performance | Year: 2016

A constitutive model has been established based on dislocation theory, work hardening and dynamic recovery theory, and softening mechanisms of dynamic recrystallization. The stress-strain curves of a bainite steel have been measured with hot compression experiments at temperatures of 1173, 1273, 1373 and 1473 K with strain rates of 0.01, 0.1, 1 and 10 s−1 on a thermo-mechanical simulator (Gleeble-1500). The material constants involved in the constitutive model have been optimized by an inverse analysis of the stress-strain curves using the method of coordinate rotation, determining the strain-stress relationship or the constitutive equation, the kinetic models of dynamic recovery and dynamic recrystallization, and a few material constants of the investigated steel. Comparison of the calculated flow stress with the experimental data suggests that the relationship between the flow stress and the strain rate, temperature, strain of the steel during hot deformation can be described by the constitutive model, and that the underlying materials science can be captured from the material constants determined by the stress-strain curves. © 2016, ASM International.


Wan X.-L.,Wuhan University of Science and Technology | Wan X.-L.,The State Key Laboratory of Refractories and Metallurgy | Li G.-Q.,The State Key Laboratory of Refractories and Metallurgy | Li G.-Q.,Hubei Collaborative Innovation Center for Advanced Steels | And 2 more authors.
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2016

The concept of phase reversion involving cold deformation of metastable austenite to generate strain-induced martensite, followed by temperature-time annealing sequence, was used to obtain grain size of nanograined/ultrafine-grained and coarse-grained austenitic stainless steels. The mechanical properties of austenitic stainless steels with different grain sizes were obtained by tensile testing, the deformation microstructure and fracture surface were analyzed by TEM and SEM observations, respectively. The results indicate that deformation twins contribute to excellent ductility in high yield strength nanograined/ultrafine-grained steel, while in the low yield strength coarse-grained steel, the high ductility is due to strain-induced martensite transformation. Interestingly, the tensile fracture of the two austensite stainless steels with different deformation mechanism is ductile fracture. The deformation mechanism from deformation twins to strain-induced martensite in the coarse-grained structure in nanograined/ultrafine-grained structures is owing to the increased stability of austenite with grain refining. © 2016, Journal of Materials Engineering. All right reserved.


Zhu C.-Y.,The State Key Laboratory of Refractories and Metallurgy | Zhu C.-Y.,Wuhan University of Science and Technology | Chen X.-H.,The State Key Laboratory of Refractories and Metallurgy | Chen X.-H.,Wuhan University of Science and Technology | And 4 more authors.
Materials Science Forum | Year: 2016

Effects of RE addition on deoxidation and desulphurization efficiency, precipitation behaviors of the inclusions, microstructure and magnetic properties of the finished sheets have been investigated for no-oriented electrical steel produced in industrial scale. The most suitable addition amount of RE alloy added in the electrical steel bearing is proposed for excellent deoxidation and desulphurization efficiency. RE added into the steel can form larger and higher melt point RE oxides, RE sulfides and RE oxysulfides inclusions removing from the bath by floating which decreases the numbers and increases the size of the fine inclusions. The average size of the inclusions remained in the steel is 0.8μm~1.4μm. RE content affects grain size by influencing number and size of fine inclusions in the finished steel sheets. The magnetic flux density of the finished steel sheets dereases with the increase of RE content while the lowest core loss of it has an optimum RE content in the steel. In the steel bearing 1.15wt% Si, the content of RE should be strictly controlled in the range from 20×10-4 wt% to 60×10-4 wt%. © 2016 Trans Tech Publications, Switzerland.


Li L.,The State Key Laboratory of Refractories and Metallurgy | Li L.,Wuhan University of Science and Technology | Liu S.,The State Key Laboratory of Refractories and Metallurgy | Liu S.,Wuhan University of Science and Technology | And 4 more authors.
Metals and Materials International | Year: 2016

A constitutive model including the kinetics of twinning and martensitic transformation has been established based on the dislocation theory and the mixture law. The stress-strain curve of a 304 stainless steel has been measured by a tensile test. The material constants for the constitutive model are then found through an inverse analysis of the stress-strain curve measured experimentally, determining the stress-strain relationship equation and the kinetics of twinning and martensitic transformation of the investigated alloy. The volume fractions of martensitic transformation have been measured by the magnetic tester of Fischer Model MP3C. It has been shown that the calculated stress-strain curve and the volume fractions of martensitic transformation are in agreement with those obtained from experimental measurements, demonstrating that the material constants found by using the stress-strain curve can capture the underlying materials science of deformation. On this basis, the influence of twins, martensitic transformation, and mechanical behavior of austenite and martensite on the strength and plasticity of the 304 stainless steel has been discussed further. © 2016 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht


Zhu C.,The State Key Laboratory of Refractories and Metallurgy | Zhu C.,Wuhan University of Science and Technology | Chen X.,The State Key Laboratory of Refractories and Metallurgy | Chen X.,Wuhan University of Science and Technology | And 6 more authors.
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2015

The precipitation behaviors of the second phase particles and their textures in the low temperature grain-oriented silicon steel are studied under different processes. The results show that not only the dispersed nanoscale spherical or ellipsoidal MnS and Cu2S precipitations are observed in the hot rolled slabs, but also SiO2, AlN and Si3N4 which are similar to MnS and Cu2S in the morphology and complex compounds that are composed by them together are observed. In the sample, precipitations at the micron scale are mainly composed by SiO2, MnS, Cu2S and AlN, and precipitations at the nanoscale are mainly composed by AlN, Si3N4, MnS and Cu2S. The number of precipitates whose size is from 0.01 μm to 0.2 μm is the largest in the hot rolled slabs, which accounts for about 90%. Compared with the conventional hot rolling slabs, the area density of the inclusions in the CSP samples is smaller, but the average size in the range of greater than 1 μm of that is larger. It will make the secondary recrystallization incomplete during the annealing process, and also it can influence the magnetic property of the products. The distribution of texture which is perpendicular to the rolling direction on cross section in the hot rolled slabs is very different. The texture of the CSP samples is relatively uniform, which is harmful to develop complete secondary recrystallization texture during the subsequent treatment process to obtain good magnetic properties. ©, 2015, Chongqing Medical University. All right reserved.

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