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Effect of Heat Input on cleavage Crack Initiation of Simulated Coarse Grain Heat-affected Zone in Microalloyed Offshore Platform Steel

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Journal of Iron and Steel Research International 2016年第10期23卷 1086-1095页

作者： Feng LU Guang-ping CHENG Feng CHAI Tao PAN Zhong-ran SHI Hang SU Cai-fu YANG School of Material Science and Engineering Anhui University of Technology Department of Structural Steel Central Iron and Steel Research Institute

The combined effects of martensite-austenite（MA）constituent and pearlite colony on cleavage crack initiation in the simulated coarse-grained heat-affected zone（CGHAZ）of V-N-Ti microalloyed offshore platform steel under different heat inputs were *** results of welding simulation,instrumented impact test,and quantitative analysis indicated that the size of the MA constituent decreased with the increase in cooling time,and by contrast,the size of the pearlite colony *** to Griffith theory,the critical sizes of cleavage microcracks were *** the increase of cooling time,the calculated microcrack size could be characterized by the size of the MA constituent first,and then fitted with the size of the pearlite ***,the calculated microcrack size variation was opposite to the microcrack initiation *** phenomenon is probably due to the combined effects of the MA constituent and pearlite colony with increasing the cooling time of the specimen′s temperature from800 to 500 ℃.

关键词： simulated coarse-grained heat-affected zone martensite-austenite constituent pearlite colony cleavage fracture V-N-Ti microaltoying

Effect of Microstructure Refinement on the Strength and Toughness of Low Alloy Martensitic Steel

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Journal of Materials Science & Technology 2007年第5期23卷 659-664页

作者： Chunfang WANG Maoqiu WANG Jie SHI Weijun HUI Han DONG National Engineering Research Center of Advanced Steei Technology Central Iron and Steel Research Institute Beijing100081 China

Martensitic microstructure in quenched and tempered 17CrNiMo6 steel with the prior austenite grain size ranging from 6 μm to 199 μm has been characterized by optical metallography （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The yield strength and the toughness of the steel with various prior austenite grain sizes were tested and correlated with microstructure characteristics. Results show that both the prior austenite grain size and the martensitic packet size in the 17CrNiMo6 steel follow a HalI-Petch relation with the yield strength. When the prior austenite grain size was refined from 199 μm to 6 μm , the yield strength increased by 235 MPa, while the Charpy U-notch impact energy at 77 K improved more than 8 times, indicating that microstructure refinement is more effective in improving the resistance to cleavage fracture than in increasing the strength. The fracture surfaces implied that the unit crack path for cleavage fracture is identified as being the packet.

关键词： Martensitic steel Grain refinement Strength Impact toughness cleavage fracture

Effect of coarse TiN inclusions and microstructure on impact toughness fluctuation in Ti micro-alloyed steel

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Journal of Iron and Steel Research International 2018年第10期25卷 1043-1053页

作者： Tao Liu Mu-jun Long Deng-fu Chen Hua-mei Duan Lin-tao Gui Sheng Yu Jun-sheng Cao Hua-biao Chen He-lin Fan State Key Laboratory of Coal Mine Disaster Dynamics and Control College of Materials Science and Engineering Chongqing University Chongqing 400044 China Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials Chongqing University Chongqing 400044 China

Toughness is an important property for steels used in engineering applications. However, recent toughness testing has shown the existence of a significant fluctuation in toughness in a single rolled plate of titanium micro-alloyed steel. The underlying causes of this fluctuation were investigated by fractography, analysis of microstructure and measurement of inclusions. Coarse and distributed TiN inclusions were responsible for the toughness variation, as they tended to act as the potential cleavage initiators to form micro-cracks. From a calculation of the local fracture stress, the critical size of coarse TiN inclusions for dominating micro-crack propagation was 4.93 μm, and similarly that of ferrite grains was 36.6μm. Under current casting and thermo-mechanically controlled processing schedules, the toughness fluctuation of rolled steel plates can be primarily attributed to the fraction of coarse TiN inclusions larger than 5μm. A corresponding relationship between impact energy and the proportion of coarse TiN inclusions was established. Finally, a normalizing treatment was applied to refine the ferrite grains of rolled steel plates. Despite the presence of coarse TiN inclusions, this refinement in ferrite grains minimized the toughness fluctuation and improved the uniformity of the impact properties of the steel plates.

关键词： Impact toughness fluctuation Ti micro-alloyed steel cleavage fracture Coarse TiN inclusion Grain refinement

A novel linear microprobe array for the fabrication of neural microelectrodes

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Science China(Technological Sciences) 2015年第2期58卷 346-351页

作者： ZHAO Shan Shan PEI Wei Hua ZHAO Hui WANG Yi Jun CHEN San Yuan CHEN Yuan Fang ZHANG He GUO Dong Mei GUI Qiang CHEN Hong Da State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Institute for Neural Computation University of California San Diego

A novel linear microprobe array(LMPA)has been developed by a conventional microfabrication method from *** LMPA leverages the properties of conventional microwire with additional features of naturally formed regular *** the help of periodic microprobe arrays and double-side V-grooves fabricated in advance between each pair of the two microprobes’rear ends,the number of microprobe units for assembly in one array can be flexibly chosen by cleavage fracture from the *** fabrication method was demonstrated and the prototype device was assessed by electrochemical impedance spectroscopy(EIS)and in vivo *** SNR of the spikes recorded was 6.

关键词： LMPA regular spacing cleavage fracture V-groove

Deformation behavior and plastic instability of boronized Al0.25CoCrFeNi high-entropy alloys

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International Journal of Minerals,Metallurgy and Materials 2020年第10期27卷 1363-1370页

作者： Jin-xiong Hou Jing Fan Hui-jun Yang Zhong Wang Jun-wei Qiao College 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

Using thermochemical treatments,boronized layers were successfully prepared on Al0.25CoCrFeNi high-entropy alloys(HEAs).The thickness of the boronized layers ranged widely from 20 to 50μm,depending on the heat treatment *** remarkably improved the surface hardness from HV 188 to HV 1265 after treating at 900°C for 9 ***,boronizing enhanced the yield strength of HEAs from 195 to 265 MPa but deteriorated the tensile *** crackings in the boride layers significantly decreased the *** insufficient work-hardening capacity essentially facilitated the plastic instability of the boronized *** decreasing substrate thickness,the fracture modes gradually transformed from dimples to quasi-cleavage and eventually to cleavage.

关键词： boronizing high-entropy alloys boride layers tensile strength cleavage fracture

fracture in sintered Sm-Co permanent magnetic materials

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Science China(Physics,Mechanics & Astronomy) 2003年第3期46卷 241-247页

作者：李安华董生智李卫 Department of Functional Materials Central Iron&Steel Research InstituteBeijing 100081China

The bending strength and fracture toughness of sintered Sm-Co permanent magnetic materials are measured. A scanning electron microscope equipped with an energy dispersive X-ray analysis system is employed to investigate the bending fractography. The fracture behavior and micromechanism are discussed. The fracture behavior of sintered Sm-Co permanent magnetic materials exhibits cleavage fracture. Some Sm-rich impurities are found in fracture plane, suggesting that the Sm-rich impurities help reduce the cleavage brittleness of sintered Sm-Co permanent magnetic materials. The possible methods for improving the strength and toughness are also proposed.

关键词： Sm-Co permanent magnents bending strength cleavage fracture

Mechanical Behavior of CrMo4 Steel With Dual-Phase Microstructure

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Journal of Iron and Steel Research International 2011年第S1期18卷 862-868页

作者： A Salemi A-H Golestaneh E Moosavi-Khoonsari Department of Metallurgy Engineering Islamic Azad University-Karaj BranchKarajIran Noor Behineh Gostar Co.Ltd.Tehran Iran

Multi-phase microstructures having good ductility may replace the conventional microstructures in different technological applications such as pressure *** properties including the fracture behavior and the service life of pressure vessels are strongly affected by the *** objective of this study was to investigate the correlation between different dual-phase microstructures and mechanical properties of 42CrMo4 (AISI 4140) *** produce the martensite-bainite (M-B),the martensite-ferrite (M-F),and the ferrite-bainite (F-B) microstructures,the step quenching heat treatment was *** properties of heat treated samples including the strength,ductility,and impact energy were *** experiments revealed a discontinuous yielding in the F-B specimen with ferritic ***\graphic results showed high concentration bright facets (BFs) on broken specimen surfaces indicating the brittle cleavage fracture was the predominant mechanism in the dual-phase microstructures.

关键词： 42CrMo4 steel dual-phase microstructures cleavage fracture

Investigation of separation phenomenon in high-toughness X70 thick-walled linepipe steel

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Baosteel Technical Research 2015年第3期9卷 35-40页

作者： DING Jianhua LIANG Xiaojun JIAO Sihai Research Institute Baoshan Iron & Steel Co.Ltd.

Separation is a commonly observed phenomenon during drop weight tear testing in high-toughness linepipe steels. Severe separation is harmful because it may cause fracturing or bursting of pipes. In this study, a quantitative measurement of separation was proposed, and using this new method, a relationship between the separation and microstructure was determined and discussed. The microstructures observed using optical and scanning electron microscopy revealed that the separation was related to the mixed ferfitic and bainitic microstructures, or rather,it was related to the carbon enrichment in bainite.

关键词： linepipe steel DWTT separation bainite thermomechanical processing cleavage fracture