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Enhanced mechanical stability of ultrafine grained steel through intercritical annealing cold rolled martensite

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Acta Metallurgica Sinica(English Letters) 2012年第6期25卷 443-452页

作者： huifang lan Xianghua LIU Linxiu DU The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China

The ultrafine grained ferritic steels possess shortage of work hardening. Fine grained high strength but low ductility due to the ferrite-martensite dual phase microstruc- ture was obtained in a microalloyed steel and low carbon steels through intercritical annealing of the cold rolled martensite. The dual phase microstructure was uniform and the ferrite grain size was smaller in the microalloyed steel resulted from the pin- ning effect of microalloyed precipitates. But ferrite grown apparently and the volume fraction of the martensite was much higher without the addition of microalloying el- ements. By introducing martensite into the fine grained ferrite, the work hardening was effectively improved, leading to better mechanical stability. As a result of the fine ferrite grain size as well as uniform distribution of the martensite, the work harden- ing was enhanced, showing better strength-ductility balance in the microalloyed dual phase steel.

关键词： Mechanical stability Fine grained dual phase steel Work hardening Strength-ductility balance

Effect of Austempering Route on Microstructural Characterization of Nanobainitic Steel

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 19-26页

作者： huifang lan Linxiu Du Na Zhou Xianghua Liu State Key Laboratory of Rolling and Automation Northeastern University Hebei Shougang Qian'an Iron & Steel Co. Ltd

A low-temperature nanobainitic steel was obtained through one-step and two-step austempering. The effect of austempering temperature, time, and route on bainitic lath width, volume fraction of retained austenite, carbon concen- tration in retained austenite, and nanohardness of bainitic lath and retained austenite was studied. Results showed that the transformation kinetics was slowed down and the bainitic lath was refined as the austempering temperature decreased from 300 to 250 C. Both coarser and finer bainitic laths were obtained with the two-step austempering, which was consistent with the lath size at 300 and 250 C austempering, respectively. X-ray diffraction analysis showed that both volume fraction of retained austenite and its carbon concentration decreased with the decrease of austempering temperature for the one-step austempering, and especially the carbon concentration is obviously increased when the two-step austempering is adopted. The nanohardness of the bainitic lath in the sample after two-step austempering treated lies between that of the samples after 300 and 250 C austempering treated. The product of tensile strength and total elongation of the two-step austempered sample is the highest, which increases monotonously with the product of retained austenite fraction and its carbon concentration. Higher strengthluctility balance may be resulted by the fine bainitic lath, high volume fraction, and high stability of retained austenite in the sample after two-step austempered.

关键词： Nanobainitic steel Stability Retained austenite Nanohardness Strength-ductility balance

High performance low cost steels with ultrafine grained and multi-phased microstructure

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Science China(Technological Sciences) 2009年第8期52卷 2245-2254页

作者： LIU XiangHua lan huifang DU LinXiu LIU WeiJie State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110004China Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang790-784Korea

Ultrafine grained ferrite was obtained through tempering cold rolled martensite with an average grain size of 200―400 nm in a low carbon and a microalloyed steel. Thermal and mechanical stability of the two steels was studied. Due to the pinning effect of microalloyed precipitates on the movement of dislocations and grain boundaries, the recrystallization and grain growth rate were retarded, and the thermal stability of ultrafine grained microstructure was improved. The ultrafine grained ferritic steel was strengthened, but its strain hardening rate was reduced. It seems that the tiny carbide precipitates have no significant effect on work hardening rate. The ultrafine grained ferrite+martensite dual phase microstructure was obtained in the microalloyed steel through intercritically annealing cold rolled martensite. The resulting multiphase microstructure has a tensile strength higher than 1.0 GPa with a yield ratio lower than 0.7. Another type of multiphase microstructure with nanoscaled lath bainite+ retained austenite was obtained through an isothermal heat treatment in low temperature bainite transformation region in high carbon steel. The tensile strength was as high as 1.64 GPa with a yield ratio of 0.84.

关键词： ultrafine grained steel multiphase high strength yield ratio

Fabrication and Microstructural Control of Nano-structured Bulk Steels: A Review

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Acta Metallurgica Sinica(English Letters) 2014年第3期27卷 508-520页

作者： Linxiu Du Shengjie Yao Jun Hu huifang lan Hui Xie Guodong Wang State Key Laboratory of Rolling and Automation Northeastern University School of Materials Science and Engineering Harbin Institute of Technology at Weihai

There exist strong interests of developing nano-grained steels because of the outstanding properties including high strength/weight ratio, wear resistance, excellent toughness, and favorable cellular activity. This article reviews the main fabrication process and microstructural control of nano-structured steels over the last decades. Severe plastic deformation is considered as an effective route of obtaining the nano-grained microstructures. The process of cold-rolling and annealing of martensitic steel is a viable method to obtain bulk nano-structured low carbon steel, while the final thickness of the cold-rolling plate is limited. According to the theoretical results of the thermal simulation studies, a novel alloy design combined with the rapid transformation and rolling process is proposed to successfully fabricate nano-grained high strength bulk steel. The refinement mechanisms are expected to be taking advantage of increase in the transformation nucleation sites and inhibiting the grain coarsening. Moreover, corresponding mechanical properties are summarized.

关键词： Nano-structured steel SPD Cold-rolling and annealing martensite RTRP Transformation mechanism Mechanical properties

Unveiling quality of clinical trial in China:from concern to confirmation

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Cancer Communications 2024年第5期44卷 576-579页

作者： Huiyao Huang Yiru Hou Hong Fang Ling Xu Yue Yu huifang Zhang Jing Zhang Yu Tang Gongtao lan Wenbao Zhang Ning Li Clinical Trials Center National Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingP.R.China School of Basic Medicine and Clinical Pharmacy China Pharmaceutical UniversityNanjingJiangsuP.R.China Department of Quality Medicine Boehringer Ingelheim(China)Investment Co LtdShanghaiP.R.China Department of Clinical Development Quality Pfizer Research and Development(China)BeijingP.R.China Department of Drug Registration National Medical Products AdministrationBeijingP.R.China Bureau of Medical Administration National Health CommissionBeijingP.R.China

The cornerstone of scientifically valid and ethically sound clinical trials is in compliance with established global quality *** China has made significant progress over the past 20 years in terms of the clinical trial quantity[1],quality and participation in multiregional trials[2],there still remain concerns regarding the trial quality,which could be associated with the self-inspection initiative in 2015[3].

关键词： clinical corners confirmation

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马氏体冷轧-回火制备超细晶钢及其热稳定性

材料研究学报 2008年第3期22卷 279-286页

作者：蓝慧芳 W.J.Liu 刘相华东北大学轧制技术及连轧自动化国家重点实验室沈阳110004 Graduate Institute of Ferrous Technology POSTECH Pohang 790-784 Korea

在低碳钢和低碳加铌、钒、钛微合金钢中,通过马氏体冷轧-回火的方法获得了尺寸为数百纳米的超细晶粒铁素体组织,研究了超细晶粒组的形成机制和热稳定性.通过马氏体相变在这些钢中引入了大量高密度位错,马氏体冷轧后位错进一步增殖,形成... 详细信息

在低碳钢和低碳加铌、钒、钛微合金钢中,通过马氏体冷轧-回火的方法获得了尺寸为数百纳米的超细晶粒铁素体组织,研究了超细晶粒组的形成机制和热稳定性.通过马氏体相变在这些钢中引入了大量高密度位错,马氏体冷轧后位错进一步增殖,形成大量位错胞状结构;在500-600℃进行的60 min回火将上述胞状结构转变成具有清晰大角晶界的超细晶粒.在回火过程中形成的微合金元素碳化物对位错运动和晶界移动具有有效的"钉扎"作用,有助于获得超细晶组织并明显提高其热稳定性.

关键词：金属材料超细晶冷轧马氏体回火微合金钢

东道国母公司的文化控制和人员控制对IJVs学习能力的影响——华南地区企业的实证研究

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科学学与科学技术管理 2009年第9期30卷 147-153页

作者：谢洪明王晓玲蓝蕙芳华南理工大学工商管理学院广州510640

在东道国母公司相对于外方母公司处于弱势的情况下,探寻其对设立在本国的跨国合资公司(International Joint Ventures,简称IJVs)的管理控制方式,是否以及如何提升IJVs的学习能力具有重要的理论价值和实践意义。研究了东道国母公司对在... 详细信息

在东道国母公司相对于外方母公司处于弱势的情况下,探寻其对设立在本国的跨国合资公司(International Joint Ventures,简称IJVs)的管理控制方式,是否以及如何提升IJVs的学习能力具有重要的理论价值和实践意义。研究了东道国母公司对在本土成立的IJVs采取的文化控制、人员控制对IJVs学习能力的影响,并以华南地区的96家IJVs为样本,运用结构方程模型进行实证研究。结果表明,东道国母公司采取的文化控制对人员控制有正向的影响关系;人员控制对IJVs的学习能力有正向的影响关系;文化控制不能直接影响IJVs的学习能力,它主要是以人员控制为中介间接地影响IJVs的学习能力。

关键词：文化控制人员控制学习能力跨国合资公司

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仔猪的科学饲养管理

农业技术与装备 2015年第4期 80-82页

作者：兰慧芳乔栋山西省朔州市畜牧兽医局山西朔州036002

仔猪包括哺乳仔猪（0~30日龄）和保育猪（30~70日龄）两个阶段。因其生长发育规律和生理特点的独特,哺乳阶段易出现环境、营养和免疫不成熟等多重应激,发病率高、死亡率也高。保育阶段常发生食欲降低、腹泻、生长缓慢等现象,降低了母猪... 详细信息

仔猪包括哺乳仔猪（0~30日龄）和保育猪（30~70日龄）两个阶段。因其生长发育规律和生理特点的独特,哺乳阶段易出现环境、营养和免疫不成熟等多重应激,发病率高、死亡率也高。保育阶段常发生食欲降低、腹泻、生长缓慢等现象,降低了母猪年生产力,明显增加了饲养成本。对此,结合仔猪的生理特点,从哺乳仔猪和保育猪两方面,探讨提高科学饲养技术和管理措施,提高仔猪的成活率。

关键词：仔猪饲养管理

铁素体区等温过程中Ti-Mo-Cu微合金钢中的共析出行为

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金属学报 2022年第3期58卷 355-364页

作者：唐帅蓝慧芳段磊金剑锋李建平刘振宇王国栋东北大学轧制技术及连轧自动化国家重点实验室沈阳110819 东北大学材料科学与工程学院沈阳110819

碳化物和Cu的共析出是提高微合金钢强度的一种有效手段,本工作利用OM和TEM研究了Ti-Mo-Cu微合金钢在不同等温温度下复合型碳化物和ε-Cu的共析出行为,利用复合析出相固溶析出模型和经典形核长大理论对Ti-Mo-Cu微合金钢的析出动力学进行... 详细信息

碳化物和Cu的共析出是提高微合金钢强度的一种有效手段,本工作利用OM和TEM研究了Ti-Mo-Cu微合金钢在不同等温温度下复合型碳化物和ε-Cu的共析出行为,利用复合析出相固溶析出模型和经典形核长大理论对Ti-Mo-Cu微合金钢的析出动力学进行了计算。结果表明,(Ti,Mo)C与ε-Cu二者独立析出,分别与铁素体基体呈N-W和K-S取向关系,在600℃时析出以ε-Cu为主,620℃发生(Ti,Mo)C与ε-Cu的共析出,而640~660℃时析出以(Ti,Mo)C相间析出为主。热动力学计算表明,在600~660℃范围内,随温度提高,(Ti,Mo)C中的Ti/Mo原子比由2.5增大到4.5,碳化物组成由Ti_(0.71)Mo_(0.29)C演变为Ti_(0.79)Mo_(0.21)C,(Ti,Mo)C与ε-Cu的析出-温度-时间(PTT)曲线存在交点,当温度低于616℃时,ε-Cu优先析出,温度在616℃附近时,发生(Ti,Mo)C与ε-Cu的共析出,当温度高于616℃时,(Ti,Mo)C优先析出,很好解释了实验现象。

关键词： Ti-Mo-Cu 微合金钢 (Ti,Mo)C ε-Cu 共析出析出动力学