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Effect of deformation parameters on the austenite Dynamic recrystallization behavior of a eutectoid pearlite rail steel

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 833-841页

作者： Haibo Feng Shaohua Li Kexiao Wang Junheng Gao Shuize Wang Haitao Zhao Zhenyu Han Yong Deng Yuhe Huang Xinping Ma Institute for Carbon Neutrality University of Science and Technology BeijingBeijing 100083China Institute for Steel Sustainable Technology Liaoning Academy of MaterialsShenyang 110004China Pangang Group Panzhihua Iron and Steel Research Institute Co.Ltd. Panzhihua 617000China

Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels.In this work,the austenite Dynamic recrystallization(DRX)behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines.The single-pass hot deformation results reveal that the prior austenite grain sizes(PAGSs)for samples with different deformation reductions decrease initially with an increase in deformation temperature.However,once the deformation temperature is beyond a certain threshold,the PAGSs start to increase.It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature,respectively.Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX.In the case of complete DRX,PAGS is predominantly determined by the deformation temperature of the final pass.It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.

关键词： eutectoid pearlite rail steel prior austenite grain size Dynamic recrystallization single-pass hot deformation three-pass hot deformation

Effect of Al_(2)O_(3)fiber on twin intersections-induced Dynamic recrystallization in fine-grained TiAl matrix composite

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Journal of Materials Science & Technology 2024年第5期172卷 1-14页

作者： Yaofeng Luo Yan Wang Li Wang Bin Liu Yong Liu State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

Dynamic recrystallization(DRX)is of great significance for the thermomechanical processing and microstructural regulation of TiAl intermetallics.However,the underlying DRX mechanism remains poorly understood.In this study,an Avrami kinetics model for DRX was established,which was capable of predicting the DRX fraction accurately.In addition,the effect of Al_(2)O_(3)short fiber on the DRX mechanisms of TiAl matrix composite during the isothermal compression was investigated for the first time.The re-sults showed that other than inhibiting DRX by particles in the TiAl matrix composites,the addition of Al_(2)O_(3)short fiber accelerated a novel DRX process,which was induced by twinning and twin intersec-tions(TDRX).Thus,this composite exhibited a higher DRX rate than that of the as-cast TiAl monolithic alloy.The origin of the twin intersection and TDRX for the composite was revealed.The stress concentration near the Al_(2)O_(3)fiber was above the critical shear stress for twinning and thus was favorable for the formation of twinning and twin intersections.The high stored strain energy at the regions of twins and twin intersections provided the driving force for TDRX.TDRX accelerated the grain refinement in the TiAl matrix near the Al_(2)O_(3)fiber.The present findings would provide a new perspective on DRX mechanisms,and provide the scientific guidance for optimizing the microstructures of TiAl matrix composites.

关键词： TiAl matrix composite Al_(2)O_(3)fiber Twin intersection Dynamic recrystallization

Continuous observation of twinning and Dynamic recrystallization in ZM21 magnesium alloy tubes during locally heated dieless drawing

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Journal of Magnesium and Alloys 2022年第3期10卷 791-805页

作者： Peihua Du Shusaku Furusawa Tsuyoshi Furushima Department of Mechanical and Biofunctional Systems Institute of Industrial ScienceThe University of Tokyo4-6-1KomabaMeguroTokyo 153-8505Japan

Compared to cold drawing,dieless drawing has shown great potential for manufacturing biodegradable Mg alloy microtubes due to the large reduction in area acquired in a single pass.However,owing to the local heating and local deformation,the deformation mechanism during dieless drawing is not clear,and thus causing difficulties in controlling the microstructure of dieless drawn tubes.For the purpose of acquiring a desired microstructure.in this study the deformation mechanism of ZM21 Mg alloy tube was clarified by conducting continuous observation of the microstructural evolution during dieless drawing.The results show that both SRX and DRX occurred during dieless drawing.SRX occurred before the plastic deformation to soften dieless drawn tubes.With increase of feeding speed,the deformation mechanism changed accordingly:(1) At the low-speed of 0.02 mm/s,the deformation mechanism was dominated by twin-slip sliding,during which {10-12} tension twins were generated inside grains to accommodate the plastic deformation by changing the crystal orientation.(2) At the intermediate-speed of 2 mm/s,a twin-DRX process related to {10-12} tension twin was observed,which was characterized by the generation of abundant {10-12} tension twins and the evolution of misorientation angle of {10-12} tension twins.Moreover,the transformation from twin-DRX to CDRX can be observed at the late stage of plastic deformation,which was attributed to the inhomogeneous conditions of dieless drawing.(3) At the high-speed of 5 mm/s,a CDRX process was observed,during which grain boundary sliding and grain tilting were observed,in addition to the gradual rotation of subgrains.These results show that during dieless drawing,DRX is not only a temperature-dependent phenomenon,but also influenced by the variation of feeding speed.

关键词： Dieless drawing Inhomogeneous condition Twining Dynamic recrystallization Microstructure evolution Magnesium alloy Twinning

Dynamic recrystallization behavior and coincidence site lattice evolution in thermal deformation of 316H stainless steel used in nuclear systems

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Journal of Iron and Steel Research(International) 2023年第9期30卷 1862-1872页

作者： Le-li Chen Rui Luo Pei Gao Tian-wei Yin Hui-xia Hao Dong-hua Sheng Tian Liu Heng-nan Ding Yu Cao Bao-sen Zhang Xiao-nong Cheng School of Materials Science and Engineering Jiangsu UniversityZhenjiang 212013JiangsuChina Technical Management Department Jiangsu Yinhuan Precision Steel Tube Co.Ltd.Yixing 214200JiangsuChina College of Materials Science and Engineering Chongqing UniversityChongqing 400045China School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167JiangsuChina

The hot deformation behavior of 316H stainless steel used in the 4th-generation nuclear systems was investigated by thermal compression tests at 1000–1150 C and 0.01–10 s^(-1).It was found that true stress firstly increased and then decreased with the increasing strain rate with a threshold of 1 s^(-1).Electron backscatter diffraction was used to analyze the microstructure evolution.Discontinuous Dynamic recrystallization(DDRX)was the dominant Dynamic recrystallization(DRX)mechanism,while continuous Dynamic recrystallization(CDRX)was the supplementary one.DDRX happened before CDRX and provided additional nucleation sites for the latter.Twin grain boundaries(R3)appeared in DRX grains due to growth accidents.As the length fraction of R3 increased,the coincidence site lattice(CSL)boundary transition began to occur,forming R9 and R27.After the occurrence of full DRX,the growth and annexation of DRX grains were easy to be promoted,in which progress both equiaxed grains and CSL boundaries disappeared.The ideal deformation microstructure with fine and uniform DRX grains,which was accompanied by a high length fraction of CSL boundaries,appeared at 1000℃–0.01 s^(-1),1050℃–0.01–0.1 s^(-1),1100℃–0.1–1 s^(-1) and 1150℃–1–10 s^(-1).That is,the deformation conditions mentioned above were the preferable thermal forming parameters for 316H stainless steel in actual productions.

关键词： 316H stainless steel Thermal compression Microstructure Dynamic recrystallization Coincidence site

{1012}twin–twin intersection-induced lattice rotation and Dynamic recrystallization in Mg–6Al–3Sn–2Zn alloy

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Journal of Magnesium and Alloys 2024年第4期12卷 1529-1539页

作者： Bin-Jiang Lv Sen Wang Fu-Hao Gao Ning Cui Yi-Nan Li Tie-Wei Xu Feng Guo School of Mechanical and Automotive Engineering Qingdao University of Technology266520China Key Lab of industrial Fluid Energy Conservation and Pollution Control Qingdao University of Technology266520China

This study investigated the formation mechanism of new grains due to twin–twin intersections in a coarse-grained Mg–6Al–3Sn–2Zn alloy during different strain rates of an isothermal compression.The results of electron backscattered diffraction investigations showed that the activated twins were primarily{1012}tension twins,and 60°boundaries formed due to twin–twin intersections under different strain rates.Isolated twin variants with 60°boundaries transformed into new grains through lattice rotations at a low strain rate(0.01 s^(−1)).At a high strain rate(10 s^(−1)),the regions surrounded by subgrain boundaries through high-density dislocation arrangement and the 60°boundaries transformed into new grains via Dynamic recrystallization.

关键词： Mg alloy Twin-twin intersection Lattice rotation Dynamic recrystallization

Dislocation characteristics and Dynamic recrystallization in hot deformed AM30 and AZ31 alloys

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Journal of Magnesium and Alloys 2022年第12期10卷 3495-3505页

作者： Hyeon-Woo Son Soong-Keun Hyun Metallic Materials Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea Department of Materials Science and Engineering Inha UniversityIncheon 22212Republic of Korea

Zn addition to Mg alloys activates non-basal slip or twinning with solute softening effects.On the other hand,the effects of the Zn solute on the macroscopic dislocation behavior and Dynamic recrystallization are not completely understood.Moreover,it is unclear ifslip can be affected by changes in the c/a ratio of solute atoms.This study was conducted to understand the solute strengthening of Zn addition and its effects on the dislocation characteristics and Dynamic recrystallization.A hot torsion test was performed on both AM30 and AZ31 alloys up to a high strain to investigate the Zn solute effect on the dislocation characteristics and Dynamic recrystallization.The dislocation components of the hot torsioned alloys were evaluated by X-ray line profile analysis and electron backscatter diffraction.The results showed that the Zn solutes slightly accelerate strain accumulation at the initial stages of hot deformation,which accelerated recrystallization at high strain.The dislocation characteristics were changed dynamically by Zn addition:fortified-type slip,dislocation arrangement and strain anisotropy parameters.The most important point was that the dislocation characteristics were changed dramatically at the critical strain for recrystallization and high strain regions.The addition of Zn also acted greatly in these strain areas.This indicates that the rapid formation of-type slip at the serrated grain boundaries occurs at the initiation of Dynamic recrystallization and the increase in the grain triple junction because grain refinement has a great influence on the dislocation characteristics at high strain.

关键词： Magnesium alloy X-ray line profile Solid solution Dislocation density Dynamic recrystallization

Processing map and Dynamic recrystallization behaviours of 316LN-Mn austenitic stainless steel

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International Journal of Minerals,Metallurgy and Materials 2023年第12期30卷 2386-2396页

作者： Shaolong Sheng Yanxin Qiao Ruzong Zhai Mingyue Sun Bin Xu School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China Key Laboratory of Electromagnetic Processing of Materials(Ministry of Education) Northeastern UniversityShenyang 110819China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

The hot deformation behaviours of 316LN-Mn austenitic stainless steel were investigated by uniaxial isothermal compression tests at different temperatures and strain rates.The microstructural evolutions were also studied using electron backscatter diffraction.The flow stress decreases with the increasing temperature and decreasing strain rate.A constitutive equation was established to characterize the relationship among the deformation parameters,and the deformation activation energy was calculated to be 497.92 k J/mol.Processing maps were constructed to describe the appropriate processing window,and the optimum processing parameters were determined at a temperature of 1107-1160℃ and a strain rate of 0.005-0.026 s^(-1).Experimental results showed that the main nucleation mechanism is discontinuous Dynamic recrystallization(DDRX),followed by continuous Dynamic recrystallization(CDRX).In addition,the formation of twin boundaries facilitated the nucleation of Dynamic recrystallization.

关键词： austenitic stainless steel processing map Dynamic recrystallization constitutive equation

Coupled CA-FE simulation for Dynamic recrystallization of magnesium alloy during hot extrusion

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Journal of Magnesium and Alloys 2022年第3期10卷 833-851页

作者： Yu-Ying He Sheng-Wen Bai Gang Fang State Key Lab of Tribology Department of Mechanical EngineeringTsinghua University100084 BeijingChina

In the present research,the Dynamic recrystallization(DRX) behavior of a newly-developed Mg-Al-Zn-RE alloy with abundant secondphase particles during hot extrusion is investigated by coupling finite element(FE) and cellular automaton(CA) models.A two-dimensional CA model is developed to quantitatively and topologically evaluate the DRX process during deformation with constant forming conditions.Considering the fact that second-phase particles with various sizes extensively exist in the studied Mg-Al-Zn-RE magnesium alloy,models of DRX nucleation and grain growth velocity are modified.The coefficients of the modified CA model are calibrated by isothermal compression experiments of the magnesium alloy.Subsequently,the CA model is coupled with FE analysis to investigate the DRX behavior during the hot extrusions of the Mg-Al-Zn-RE alloy.The DRX behavior of the magnesium alloy at different stages and positions of extruded plates is simulated by the established model.Finer grains near the edge than in the inner of the plates result from higher strain and strain rate.The influence of extrusion conditions on microstructural evolution is explored.Under the employed forming conditions,average grain size decreases 28-62 times from as-cast and solution-treated to as-extruded state due to grain refinement by DRX.With increasing initial billet temperature or extrusion speed,average grain size increases.The finest grains are obtained at the initial billet temperature of 623 K and the extrusion speed of 7.83 mm/s.Low initial billet temperature or high extrusion speed benefits homogeneous grain distribution.The simulated results are in good agreement with experimental ones.

关键词： Cellular automaton Finite element Dynamic recrystallization Extrusion Magnesium alloy

Unveiling the twinning and Dynamic recrystallization behavior and the resultant texture evolution in the extruded Mg-Bi binary alloys during hot compression

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Journal of Materials Science & Technology 2022年第10期105卷 274-285页

作者： Yu-qin Zhang Wei-li Cheng Hui Yu Hong-xia Wang Xiao-feng Niu Li-fei Wang Hang Li School of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of Education Taiyuan University of TechnologyTaiyuan 030024China School of Materials Science and Engineering Hebei University of TechnologyTianjin 300132China

The twinning behavior, Dynamic recrystallization(DRX) mechanism and the resultant texture evolution of the extruded Mg-xBi(x=0.5 wt.%, 2.0 wt.%) alloys were systematically investigated during hot compression at the strain rate of 10 s^(-1) and temperature of 200℃. The results indicate that the types and intensities of the texture are greatly dependent on the twining behavior and DRX mechanism. At the initial stage, the evolution of texture is mainly domination by the formation and variation of {1012} extension twins, which is benefcial to the compression direction(CD)-tilted basal texture. With an increase in the strain, the texture evolution is more greatly regulated by the DRX mechanism. Besides, the pyramidal slip and basal slip are activated during the compression process, resulting in the Schmid factors(SF) of pyramidal slip remain at ~0.4 and the average SFs for basal slip increase from 0.2 to0.34 as the strain increase. These fndings provide a new insight into controlling the texture of wrought Mg-Bi-based alloys during hot deformation processing.

关键词： Wrought Mg-Bi alloys Hot deformation Twinning Dynamic recrystallization Dislocation slip Texture