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Journal of Magnesium and Alloys 2022年第11期10卷 3205-3216页

作者： Pengcheng Guo Xiao Liu biwu zhu Wenhui Liu Liqiang Zhang School of Mechanical and Electrical Engineering Central South University of Forestry and TechnologyChangsha 410004China School of Material Science and Engineering Hunan University of Science and TechnologyXiangtanHunan 411201China

Ultra-high strain rate impact tests were conducted by Split-Hopkinson pressure bar to investigate the microstructure evolution and impact deformation mechanism of a solution treated casting AM80 Mg alloy at 25, 150 and 250 ℃ with a strain rate of 5000 s^(-1). The microcrack and dynamic recrystallization(DRX) preferentially nucleate at grain boundary(GB) and twin boundary(TB), especially at the intersections between GBs and TBs, and then propagate along twin direction. In contrast, the adiabatic shear bands preferentially occur at high-density twined regions. At 25 ℃, the dominated deformation mechanisms are basal slip and twinning. As deformation temperature increases to 150and 250℃, the deformation gradually shifts to be dominated by a coordinated mechanism among non-basal slip, twinning and DRX. The flow stress behavior and deformation mechanism indicate that the degree of decrease in flow stress with temperature is associated with the change of deformation mode.

关键词： AM80 mg alloy Deformation mechanism Ultra-high strain rate Twinning Dynamic recrystallization

Unveiling the mechanical response and accommodation mechanism of pre-rolled AZ31 magnesium alloy under high-speed impact loading

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Journal of Magnesium and Alloys 2022年第4期10卷 1096-1108页

作者： Xiao Liu Hui Yang biwu zhu Yuanzhi Wu Wenhui Liu Changping Tang Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtanHunan 411201China Research Institute of Automobile Parts Technology Hunan Institute of TechnologyHengyangHunan 421002China

Split Hopkinson pressure bar(SHPB)tests were conducted on pre-rolled AZ31 magnesium alloy at 150–350℃ with strain rates of 2150s-1,3430s^(-1) and 4160s-1.The mechanical response,microstructural evolution and accommodation mechanism of the pre-rolled AZ31 magnesium alloy under high-speed impact loading were investigated.The twin and shear band are prevailing at low temperature,and the coexistence of twins and recrystallized grains is the dominant microstructure at medium temperature,while at high temperature,dynamic recrystallization(DRX)is almost complete.The increment of temperature reduces the critical condition difference between twinning and DRX,and the recrystallized temperature decreases with increasing strain rate.The mechanical response is related to the competition among the shear band strengthen,the twin strengthen and the fine grain strengthen and determined by the prevailing grain structure.The fine grain strengthen could compensate soften caused by the temperature increase and the reduction of twin and shear band.During high-speed deformation,different twin variants,introduced by pre-rolling,induce different deformation mechanism to accommodate plastic deformation and are in favor for non-basal slip.At low temperature,the high-speed deformation is achieved by twinning,dislocation slip and the following deformation shear band at different deformation stages.At high temperature,the high-speed deformation is realized by twinning and dislocation slip of early deformation stage,transition shear band of medium deformation stage and DRX of final deformation stage.

关键词： Mechanical response Pre-twinning Accommodation mechanism Pre-rolled AZ31 magnesium alloy High-speed impact loading

Modeling of the flow stress behavior and microstructural evolution during hot deformation of Mg-8Al-1.5Ca-0.2Sr magnesium alloy

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Journal of Magnesium and Alloys 2014年第2期2卷 133-139页

作者： Xiao Liu Luoxing Li biwu zhu State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082HunanChina College of Mechanical and Electrical Engineering Hunan University Science and TechnologyXiangtan 411002HunanChina

Hot compression tests of Mg-8Al-1.5Ca-0.2Sr magnesium alloy were performed on the Gleeble-1500 machine at temperatures of 300,350,400,and 450℃and strain rates of 0.01,0.1 and 1 s^(−1).The flow stress behavior and microstructural evolution were followed.The work hardening was derived according to the Laasraoui-Jonas model.An improved approach,which considered the influence of yield stress on flow stress and the effect of grain boundary(GB)migration on the evolution of dislocation density during compression,was used to simulate the microstructural evolution,the flow stress and the volume fraction recrystallized of Mg-8Al-1.5Ca-0.2Sr magnesium alloy.The simulated results are in good agreement with experimental results.

关键词： Magnesium alloy Work hardening Cellular automata Volume fraction recrystallized Microstructure

激光熔化沉积Al-Mg-Sc-Zr合金单熔道成形质量预测

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中国有色金属学报 2024年第4期34卷 1010-1021页

作者：肖罡李伟奇谢莉路超刘筱朱必武杨钦文湖南科技大学机电工程学院湘潭411201 江西铜业技术研究院有限公司南昌330096 湖南大学机械与运载工程学院长沙410082 广东海洋大学材料科学与工程学院阳江529559

本研究探讨了激光熔化沉积(LMD)工艺参数对Al-Mg-Sc-Zr合金单熔道成形质量的影响,并采用BP神经网络模型和改进的PSO-BP神经网络模型预测了不同工艺参数下的成形孔隙率。结果表明:Al-Mg-Sc-Zr合金的LMD单熔道成形孔隙率,随着激光线能量... 详细信息

本研究探讨了激光熔化沉积(LMD)工艺参数对Al-Mg-Sc-Zr合金单熔道成形质量的影响,并采用BP神经网络模型和改进的PSO-BP神经网络模型预测了不同工艺参数下的成形孔隙率。结果表明:Al-Mg-Sc-Zr合金的LMD单熔道成形孔隙率,随着激光线能量密度的增加呈现先上升后下降再上升的趋势,在175 J/mm^(2)时孔隙率达到最小值,仅为1.38%。在相同的送粉工艺参数下,LMD成形熔道宽度和熔道深度均与激光功率呈现出正相关性,而熔道高度和熔道深度均与扫描速率呈现出负相关性。相较于BP神经网络模型,改进的PSO-BP神经网络模型的平均绝对误差降低了29.69%,平均相对误差降低了19.42%,均方误差降低了19.02%,相关系数提升了63.44%。

关键词：激光熔化沉积 Al-Mg-Sc-Zr合金熔池质量孔隙率神经网络

The flow behavior in as-extruded AZ31 magnesium alloy under impact loading

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Journal of Magnesium and Alloys 2018年第2期6卷 180-188页

作者： biwu zhu Xiao Liu Chao Xie Wenhui Liu Changping Tang Liwei Lu Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 411201China The Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China

As-extruded AZ31 magnesium alloy samples were compressed at ambient temperature and strain rates of 1000-3000 s^(−1).The fracture surfaces of cracked samples,the evolution of microstructures and macrotextures were detected.The received flow curves exhibit an abnormal behavior at strain rates above 1500 s^(−1).A strain constitutive model based on strain equivalent principle was applied to analyze the flow curves of the damaged samples.The results indicate that the abnormal flow behaviors of the fractured samples are related to the increasing area of crack surfaces,and kinetic energy during dynamic crack nucleation and propagation.The initiation of the micro-crack also causes obvious flow softening in the cracked samples.The shapes of flow stresses of the intact samples are affected by twinning.©2018 Published by Elsevier B.V.on behalf of Chongqing University.

关键词： Magnesium alloy Flow behavior Fracture Micro-crack Twinning.

Unveiling the underlying mechanism of forming edge cracks upon high strain-rate rolling of magnesium alloy

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Journal of Materials Science & Technology 2020年第15期47卷 59-65页

作者： biwu zhu Xiao Liu Chao Xie Jing Su Pengcheng Guo Changping Tang Wenhui Liu Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 411201China Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Strafie 1Dusseldorf40237Germany College of Mechanical and Electrical Engineering Central South University of Forestry and TechnologyChangsha 410004China Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 477207China

In the current study,high strain-rate rolling(≥10 s-1) has been successfully employed to produce Mg-3 A1-1 Zn alloy sheets to a high reduction of 82% with a fine grain structure in a single pass.The underlying mechanism of forming primary and secondary edge cracks has been investigated.It is found that dynamic recrystallization(DRX) induced by subgrains tends to blunt cracks,while twinning-induced D RX is mainly observed around sharp crack tips.The motion of emitted dislocations from blunted cracks is inhibited by the DRX grain boundaries.This,on one hand,increases local work hardening,and on the other hand,causes stress concentration alo ng grain boundaries especially in the triple junctions leading to the formation of secondary cracks.

关键词： Edge crack Secondary crack High strain-rate rolling AZ31 magnesium alloy Dynamic recrystallization

中高应变速率轧制AZ31镁合金板的抗拉强度预测

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中国有色金属学报 2024年第6期34卷 1998-2007页

作者：朱必武蒋昊刘筱郭鹏程魏福安徐从昌李落星湖南科技大学机电工程学院高功效轻合金构件成形技术及耐损伤性能评价湖南省工程研究中心湘潭411201 青海大学部省合建盐湖化工大型系列研究设施西宁810016 湖南大学重庆研究院重庆401135 集美大学海洋装备与机械工程学院厦门361021

本文采集了不同轧制温度、应变速率以及压下量等三个工艺参数下中高应变速率轧制的AZ31镁合金抗拉强度的27组样本,通过惯性权重、学习因子的改进和引入变异操作对PSO-BP神经网络进行改进,并与BP、PSO-BP神经网络对比,进行抗拉强度的预... 详细信息

本文采集了不同轧制温度、应变速率以及压下量等三个工艺参数下中高应变速率轧制的AZ31镁合金抗拉强度的27组样本,通过惯性权重、学习因子的改进和引入变异操作对PSO-BP神经网络进行改进,并与BP、PSO-BP神经网络对比,进行抗拉强度的预测。结果表明:BP神经网络不能预测AZ31镁合金抗拉强度的非线性变化,PSO-BP神经网络和改进的PSO-BP(IPSO-BP)神经网络均能较好地预测AZ31镁合金抗拉强度的非线性变化;这三个模型中IPSO-BP神经网络预测最为准确,相较于PSO-BP神经网络,其平均绝对误差从15.3764降低至3.4288,平均相对误差从5.94%降低至1.32%,均方误差从251.3662降低至20.7199,相关系数从0.7753提高至0.8937;通过Pearson相关性计算判断出应变速率、压下量对抗拉强度的影响均大于轧制温度,而应变速率与抗拉强度呈负相关关系,压下量与抗拉强度呈正相关关系。

关键词： AZ31镁合金神经网络轧制工艺抗拉强度 Pearson相关系数

Coordinated Control of Fine-Particle and Ozone Pollution by the Substantial Reduction of Nitrogen Oxides

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Engineering 2022年第8期8卷 13-16页

作者： biwu Chu Yan Ding Xiang Gao Junhua Li Tingyu zhu Yunbo Yu Hong He State Key Joint Laboratory of Environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China Center for Excellence in Regional Atmospheric Environment Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China University of the Chinese Academy of Sciences Beijing 100049China Chinese Research Academy of Environmental Sciences Beijing 100012China State Environmental Protection Engineering Center for Coal-Fired Air Pollution Control Zhejiang UniversityHangzhou 310027China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China

1.Introduction In recent years,the air quality in China has improved significantly.In many cities,however,the concentration of fine particulate matter(PM_(2.5))remains higher than the secondary-level national ambient air quality standard(NAAQS level-2,35μg·m^(-3),GB3095-2012[1])and much higher than the first-level NAAQS(15μg·m^(-3),GB3095-2012[1])and the World Health Organization(WHO)air quality guidelines(5μg·m^(-3)).

关键词： Pollution Ozone ambient

叙事之艺与伦理之思的有机交融——《麦克尤恩的小说创作及其伦理价值研究》述评

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山东外语教学 2024年第3期45卷 129-133页

作者：朱慧敏刘茂生广东外语外贸大学英语语言文化学院广东广州510420

尚必武教授于2023年出版的新著《麦克尤恩的小说创作及其伦理价值研究》深入探讨了英国作家伊恩·麦克尤恩的小说创作,聚焦于作品所呈现的叙事特色和伦理主题,是麦克尤恩研究的重要成果。该著作挖掘了麦克尤恩作品隐含在叙事艺术背后的... 详细信息

尚必武教授于2023年出版的新著《麦克尤恩的小说创作及其伦理价值研究》深入探讨了英国作家伊恩·麦克尤恩的小说创作,聚焦于作品所呈现的叙事特色和伦理主题,是麦克尤恩研究的重要成果。该著作挖掘了麦克尤恩作品隐含在叙事艺术背后的伦理内核,剖析了小说中的伦理问题和伦理困境。尚必武教授细致解读麦克尤恩作品,关注被学界所忽视的伦理关切,呈现其中的伦理诉求。该著极具学术深度,特色鲜明,表达了中国本土视角下的研究立场,实现了中外研究平等对话,是理解麦克尤恩作品、推动中外文学研究交流与互动的力作。

关键词：伊恩·麦克尤恩小说创作叙事艺术伦理思想伦理价值

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铝合金薄壁压铸件研究现状及进展

特种铸造及有色合金 2016年第9期36卷 931-934页

作者：朱必武刘筱湖南科技大学高温耐磨材料及制备技术湖南省国防科技重点实验室湖南科技大学难加工材料高效精密加工湖南省重点实验室

对铝合金薄壁压铸件进行了回顾与分析,着重探讨了近年来的研究热点——铝合金薄壁压铸件应用现状,合金材料的研究现状,以及数值仿真技术存在的问题。

关键词：铝合金薄壁件压铸整体成形数值仿真