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Constitutive Modeling for Thixoforming of 9Cr18 Semi-solid Alloy and 3D Forecast Mapping

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Journal of Iron and Steel Research International 2016年第12期23卷 1309-1315页

作者： Ya-ping LI ren-bo song Yong-jin WANG School of Materials Science and Engineering University of Science and Technology Beijing

Thixotropic Compression tests were carried out on 9Cr18 semi-solid alloy through Gleeble-1500 thermal simulation machine. According to the experiment analysis, macro separation occurred during thixoforming. The liquid film was extruded outside to the surface and solidified to form eutectic structure. The solid particles were connected with each other and underwent plastic deformation. According to the comparison between Zhou-Guan model and modified Zhou-Guan model, it could be observed that the adding of thixotropic factor played an important role in the regression and the latter one was more credible. The modified Zhou-Guan model could well describe the thixoforming behavior. 3D forecast mapping was built for 9Cr18 semi solid alloy in thixoforming temperature range. It would provide valuable information for selecting process parameters during thixoforming in the manufacture process.

关键词： thixoforming constitutive model liquid fraction thixotropic factor 3D forecast

Hot ductility behavior of a Fe-0.3C-9Mn-2Al medium Mn steel

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 422-429页

作者： Yong-jin Wang Shuai Zhao ren-bo song Bin Hu School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China

The hot ductility of a Fe-0.3C-9Mn-2Al medium Mn steel was investigated using a Gleeble3800 thermo-mechanical *** tensile tests were conducted at different temperatures(600-1300℃)under a constant strain rate of 4×10^(−3)s^(−1).The fracture behavior and mechanism of hot ductility evolution were *** showed that the hot ductility decreased as the temperature was decreased from 1000℃.The reduction of area(RA)decreased rapidly in the specimens tested below 700℃,whereas that in the specimen tested at 650℃was lower than 65%.Mixed brittle-ductile fracture feature is reflected by the coexistence of cleavage step,intergranular facet,and dimple at the *** fracture belonged to ductile failure in the specimens tested between 720-1000℃.Large and deep dimples could delay crack *** change in average width of the dimples was in positive proportion with the change in *** wide austenite-ferrite intercritical temperature range was crucial for the hot ductility of medium Mn *** formation of ferrite film on austenite grain boundaries led to strain *** point elongation occurred at the austenite-ferrite intercritical temperature range during the hot tensile test.

关键词： medium Mn steel hot ductility reduction of area fracture behavior microstructure characterization

Wear behavior of bainite ductile cast iron under impact load

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International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 871-877页

作者： Ting Sun ren-bo song Fu-qiang Yang Chun-jing Wu School of Materials Science and Engineering University of Science and Technology Beijing

The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces＇ micro-hardness profiles. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were used to observe the wom surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20℃, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20℃ is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity （TRIP） phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.

关键词： cast iron continuous cooling wear behavior impact loads martensitic transformations

Effects of Temperature and Strain Rate on Solid-/Liquid-Phase Flow Behavior of 9Cr18 Steel During Thixoforging

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Acta Metallurgica Sinica(English Letters) 2017年第6期30卷 567-575页

作者： Yong-Jin Wang ren-bo song Ya-Ping Li Qiang Chen School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Mining Design and Research Institute of Anshan Iron&Steel Groups Corporation Anshan Anshan 114002China

A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase flow behavior were discussed. The results showed that functional gradient properties of the 9Cr18 steel could be obtained after thixoforging. Changes of microstructure along radial direction could be obtained. Solid austenite was retained after fast cooling, and the liquid film enriched in alloying elements was extruded outside to form a dendrite skin layer. As temperature increased, more molten liquid formed during thixoforging. A heterogeneous flow phenomenon was activated as free liquid channels were formed. The macro-separation of solid and liquid phases was critical for the formation of functional gradient properties. Above 1300 ℃, full dendrite skin layer could be formed. The strain rate affected the thixotropic property via influencing the deformation time of thixoforging. In the presence of lower strain rates, there was more time for the flow of liquid metal, which was the key to the extension of the thixotropic stage. High temperatures and low strain rates contributed to the formation of full skin layer for the designed specimen. The average thickness of skin layer for current specimen could be over 1000 ktm when thixoforged at 1340 ℃ and under a strain rate of 0.02 s^-1.

关键词： 9Cr18 steel Thixoforging Processing parameters Functional gradient property

Hot Deformation and Dynamic Recrystallization Behavior of Austenite-Based Low-Density Fe–Mn–Al–C Steel

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Acta Metallurgica Sinica(English Letters) 2016年第5期29卷 441-449页

作者： Ya-Ping Li ren-bo song Er-Ding Wen Fu-Qiang Yang School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China R&D Center BAIC Motor Corporation LTDBeijing 101300China

The hot deformation and dynamic recrystallization （DRX） behavior of austenite-based Fe-27Mn-ll.5A1- 0.95C steel with a density of 6.55 g cm-3 were investigated by compressive deformation at the temperature range of 900-1150 ℃ and strain rate of 0.01-10 s-1. Typical DRX behavior was observed under chosen deformation conditions and yield-point-elongation-like effect caused by DRX of 6-ferrite. The flow stress characteristics were determined by DRX of the 6-ferrite at early stage and the austenite at later stage, respectively. On the basis of hyperbolic sine function and linear fitting, the calculated thermal activation energy for the experimental steel was 294.204 kJ mo1-1. The occurrence of DRX for both the austenite and the 6-ferrite was estimated and plotted by related Zener-Hollomon equations. A DRX kinetic model of the steel was established by flow stress and peak strain without considering dynamic recovery and 6-ferrite DRX. The effects of deformation temperature and strain rate on DRX volume fraction were discussed in detail. Increasing deformation temperature or strain rate contributes to DRX of both the austenite and the 6-ferrite, whereas a lower strain rate leads to the austenite grains growth and the 6-ferrite evolution, from banded to island-like structure.

关键词： Fe-Mn-AI-C steel Hot deformation Dynamic recrystallization Yield-point-elongation-likeeffect

Enhanced Strength and Corrosion Resistance of Mg–2Zn–0.6Zr Alloy with Extrusion

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Acta Metallurgica Sinica(English Letters) 2019年第1期32卷 10-22页

作者： Luan-Xiang Wang ren-bo song Chang-Hong Cai Jing-Yuan Li School of Materials Science and Engineering University of Science and Technology Beijing

The microstructure, mechanical properties and corrosion behavior of Mg–2 Zn–0.6 Zr alloy under the as-cast and asextruded conditions were investigated. Microstructure analysis indicated the remarkable grain refinement by extrusion, as well as notable reductions in volume fraction and size of precipitate phases. As compared with the as-cast alloy, the asextruded alloy exhibited better mechanical performance, especially in yield strength which was promoted from 51 to 194 MPa. Refined grains, dispersive precipitate phases and texture were thought to be the main factors affecting the improved performance in strength. The electrochemical measurement and immersion test revealed the corrosion rate of Mg–2 Zn–0.6 Zr alloy by extrusion decreased from 1.68 to 0.32 mm/year. The reasons for the enhanced corrosion resistance were mainly attributed to the decreased volume fraction and Volta potential of the precipitate phases, the refinement of the grain size, as well as the formation of more protective corrosion film.

关键词： Mg–2Zn–0.6Zr Extrusion Strength Corrosion behavior

Abrasive Wear Behavior and Mechanism of High Chromium Cast Iron

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Journal of Iron and Steel Research International 2015年第1期22卷 84-90页

作者： Ting SUN ren-bo song Xu WANG Peng DENG Chun-jing WU School of Materials Science and Engineering University of Science and Technology Beijing

The abrasive wear behavior of high chromium cast iron （containing 12.9 mass% chromium） austenitized at 1 050 ℃ for 2 h and austempered in salt bath at 320 ℃ for 4 h was evaluated. Abrasive wear was performed using alumina abrasive under four different loads, namely 50, 100, 150, and 200 N, for 36000 cycles. The worn surfaces and wear debris were analyzed by scanning electron microscopy, laser confocal microscopy and X-ray diffraction. Micro hard- ness profiles were also obtained in order to analyze the strain-hardening effects beneath the contact surfaces. Results indicate that the retained austenite in high chromium cast iron has experienced induced martensitic transformation af- ter tests, for small amounts of retained austenite could be detected by X-ray diffraction. In addition, there is a close relationship between wear mechanism and test load. Under the condition of lower test load, the wear mechanism is an uninterrupted and repeated process, during which matrix is cut at first and then fine carbides flake off. As to high- er test load, scratching and spalling induced by cleavage fracture of blocky carbide are the wear mechanism.

关键词： high chromium cast iron abrasive wear wear mechanism wear behavior martensitic transformation

Abrasive Wear Behaviors of Light-weight Austenitic Fe-24Mn-7Al-1C Steel and Mn13Cr2 Steel

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Journal of Iron and Steel Research International 2016年第8期23卷 857-866页

作者： Shi-guang PENG ren-bo song Zhi-dong TAN Chang-hong CAI Ke GUO Zhong-hong WANG School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083China School of Materials Science and Engineering University of Science and Technology Liaoning Anshan 117022 Liaoning China Angang Group Mining Design and Research Institute Anshan 114004 Liaoning China

The impact abrasive wear behaviors of light-weight austenitic Fe-24Mn-7Al-1Csteel with increasing impact wear conditions were studied by comparing with the modified Hadfield（Mn13Cr2）*** tests were performed with the MLD-10 abrasive wear testing *** parameters such as impact energy,impacting frequency and wear time were *** explore the abrasive wear behaviors under different impact energies,the parameters including mass loss,wear resistance and hardness were evaluated in *** microstructures of the steels were further analyzed using optical microscopy（OM）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and X-ray diffraction（XRD）.Results showed that the light-weight austenitic Fe-24Mn-7Al-1Csteel had a better wear resistance than Mn13Cr2 steel under the impact energy *** wear resistance of light-weight austenitic Fe-24Mn-7Al-1Csteel was about 1.09-1.17 times as high as that of Mn13Cr2 steel under low and medium impact energy（0.5-2.0J）conditions,and 1.41 times under high impact energy（4.0J）*** Mn13Cr2 steel,the evolution of dislocation substructure with increasing impact energy showed typical stacking fault,interaction of twins and dislocations,as well as mechanical *** high work-hardening rate in Fe-24Mn-7Al-1Csteel was caused by Taylor lattice and high density of dislocation tangles.

关键词： twins dislocation hardness abrasive steels hardening stacking refinement austenite stainless

Nonlocal symmetries,soliton-cnoidal wave solution and soliton molecules to a(2+1)-dimensional modified KdV system

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Communications in Theoretical Physics 2024年第4期76卷 14-21页

作者： Jianyong Wang bo ren Department of Mathematics and Physics Quzhou UniversityQuzhou 324000China Department of Mathematics Zhejiang University of TechnologyHangzhou 310014China

A(2+1)-dimensional modified KdV(2DmKdV)system is considered from several ***,residue symmetry,a type of nonlocal symmetry,and the Bäcklund transformation are obtained via the truncated Painlevéexpansion ***,the residue symmetry is localized to a Lie point symmetry of a prolonged system,from which the finite transformation group is ***,the integrability of the 2DmKdV system is examined under the sense of consistent tanh expansion ***,explicit soliton-cnoidal wave solutions are ***,abundant patterns of soliton molecules are presented by imposing the velocity resonance condition on the multiple-soliton solution.

关键词： soliton-cnoidal wave solution nonlocal symmetry soliton molecule (2+1)-dimensional modified KdV system