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Challenges and opportunities in the production of magnesium parts by directed energy deposition processes

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Journal of Magnesium and Alloys 2024年第5期12卷 1663-1686页

作者： gürel Cam Ali günen Iskenderun Technical University Faculty of Engineering and Natural SciencesDepartment of Mechanical Engineering31200 Iskenderun-HatayTurkey Iskenderun Technical University Faculty of Engineering and Natural SciencesDepartment of Metallurgy and Materials Engineering31200 Iskenderun-HatayTurkey

Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight,high specific strength,and corrosion resistance,making them attractive for applications in medical,aerospace,automotive,and other transport ***,their widespread application is hindered by their low formability at room temperature due to limited slip *** Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high *** casting methods benefit from established process optimization techniques for these problems,additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations,potentially enabling easier optimization of anisotropy properties in certain *** metal additive manufacturing(MAM)technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts,they in general exhibit superior properties than the cast ***,MAM is a promising technique to produce Mg alloy *** energy deposition processes,particularly wire arc directed energy deposition(wa-DED),have emerged as an advantageous additive manufacturing(AM)technique for metallic materials including magnesium alloys,offering advantages such as high deposition rates,improved material efficiency,and reduced production costs compared to subtractive ***,the inherent challenges associated with magnesium,such as its high reactivity and susceptibility to oxidation,pose unique hurdles in the application of this *** review paper delves into the progress made in the application of DED technology to Mg-alloys,its challenges,and ***,the predominant imperfections,notably inhomo

关键词： Additive manufacturing DED processes Arc-DED Wire arc additive manufacturing(waAM) 3-D printing High deposition rate

热辅助超声滚压温度场参数影响激光熔覆涂层表面粗糙度研究

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表面技术 2024年第5期53卷 149-155页

作者：张常胜沈学会罗辉姜永泉齐鲁工业大学(山东省科学院)机械与汽车工程学院济南250353 山东建筑大学机电工程学院济南250101 浙江晶鸿精密机械制造有限公司浙江上虞312300 山东黄金矿业(莱州)有限公司三山岛金矿山东烟台261400

目的降低激光熔覆涂层的表面粗糙度。方法采用激光熔覆技术制备铁基激光熔覆涂层,采用超声温滚压耦合热处理工艺对熔覆层进行熔覆后强化加工,重点研究温度场参数对成形表面粗糙度的影响,通过方差分析(ANOVA)确立参数显著性,同时利用响... 详细信息

目的降低激光熔覆涂层的表面粗糙度。方法采用激光熔覆技术制备铁基激光熔覆涂层,采用超声温滚压耦合热处理工艺对熔覆层进行熔覆后强化加工,重点研究温度场参数对成形表面粗糙度的影响,通过方差分析(ANOVA)确立参数显著性,同时利用响应曲面法(RSM)构建温度场参数影响铁基涂层表面粗糙度的预测模型,并进行参数优化。结果加热温度和保温时间对成形试样表面粗糙度的影响显著。在实验参数范围内,试样的表面粗糙度与加热温度呈正相关,与保温时间呈负相关。实验结果表明,在相同保温时间下,在加热温度100、250、400℃条件下试样的表面粗糙度Ra分别为0.237、0.158、0.096μm;在相同加热温度下,在保温时间为0.5、1、2 h条件下试样的表面粗糙度Ra分别为0.156、0.164、0.170μm。可见与保温时间相比,加热温度对涂层表面粗糙度的影响更显著。参数优化分析结果表明,在实验参数范围内,在400℃加热温度和0.5 h保温时间条件下,试样具有最小的表面粗糙度Ra(0.089μm)。结论相较于车削及常温滚压工艺,采用超声温滚压耦合热处理工艺可进一步降低激光熔覆涂层的表面粗糙度,在实验参数范围内,加热温度400℃和保温时间0.5 h是最优的温度场参数组合。

关键词：超声滚压温塑性增材制造表面粗糙度热处理铁基合金

Physico-Chemical Characterization of Wood Ash for Agronomic Purposes

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Journal of Agricultural Chemistry and Environment 2024年第2期13卷 235-250页

作者： Ayi Kévin Ajavon Bassaï Magnoudéwa Bodjona Diyakadola Dihéénane Bafai Laboratory waste Management Treatment and Recovery (GTVD) Faculty of Sciences University of Lome Lome Togo

The oil refinery of the food products company SOPAL, located in the port area of TOgO, produces an average of 200 kg of eucalyptus wood ash per day. This ash is stored in large quantities within the premises of the refinery, without any disposal solution. The aim of this study is to identify the physico-chemical properties of SOPAL’s wood ash for agronomic valorization. Physico-chemical analyses reveal the presence of major and secondary elements such as potassium (15.71 g/kg DM), phosphorus (27.90 g/kg DM), calcium (9.76 g/kg DM), magnesium (0.03 g/kg DM), sodium (1.24 g/kg DM), iron (1.49 g/kg DM) and manganese (7.82 g/kg DM). The pH is alkaline (12.97) with fairly high conductivity (24.10 mS/Cm). Heavy metals identified are cobalt (0.19 mg/kg DM), cadmium (0.10 mg/kg DM), lead (1.14 mg/kg DM), copper (19.77 mg/kg DM) and nickel (12.82 mg/kg DM). The results show that the ash contains considerable amount of major and secondary elements for agronomic uses.

关键词： Industry Wood Ash Heavy Metals Valorization

青藏高原多年冻土微生物残体碳的分布特征及其驱动因素

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科学通报 2024年第7期69卷 925-938页

作者：贺美秦书琪冯雪徽张帆赵佳宁杨元合中国科学院植物研究所植被与环境变化国家重点实验室北京100093 国家植物园北京100093 中国科学院大学资源与环境学院北京100049

微生物残体碳是土壤稳定碳库的重要组成部分,对土壤有机碳(soil organic carbon,SOC)的贡献可达50%以上.然而,由于缺乏大尺度观测证据,目前学术界对多年冻土微生物残体碳分布特征及其驱动因素的认识十分有限.本研究基于野外样带调查和... 详细信息

微生物残体碳是土壤稳定碳库的重要组成部分,对土壤有机碳(soil organic carbon,SOC)的贡献可达50%以上.然而,由于缺乏大尺度观测证据,目前学术界对多年冻土微生物残体碳分布特征及其驱动因素的认识十分有限.本研究基于野外样带调查和室内分析相结合的方法,揭示了青藏高原多年冻土微生物残体碳的空间分布特征,对比了冻土层与活动层微生物残体碳对SOC的贡献差异.在此基础上,结合气候、土壤变量和微生物属性测定,探究了多年冻土微生物残体碳含量空间变异的驱动因素.结果显示,多年冻土总微生物残体碳、真菌和细菌残体碳含量均呈现自研究区西部向东部递增的趋势.平均而言,冻土层总微生物残体碳含量为2741.0±815.3 mg/kg(平均值±标准误差),占SOC的比例为13.2%±1.1%;真菌残体碳的含量及其对总微生物残体碳的贡献均显著高于细菌.冻土层总微生物残体碳和真菌残体碳的含量与贡献均显著低于活动层;冻土层细菌残体碳含量显著低于活动层,但其对SOC的贡献与活动层无显著差异.结构方程模型分析的结果显示,多年冻土含水率和微生物的生物量是影响多年冻土微生物残体碳含量空间变异的直接因素,气候因素则起着间接作用.总体来讲,上述结果意味着微生物残体碳是多年冻土碳的重要来源,其变化可能会影响多年冻土碳循环与气候变暖之间的正反馈关系.

关键词：碳循环多年冻土微生物残体碳真菌残体碳细菌残体碳

From genetic Mapping to Molecular Breeding： genomics Have Paved the Highway

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Molecular Plant 2016年第7期9卷 959-960页

作者： xuehui Huang National Center for gene Research CAS Center for Excellence of Molecular Plant Sciences Institute of Plant Physiology and Ecology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Shanghai 200233 China

Owing to the recent advances in sequencing technology, genetic mapping of mutations has been revolutionized by whole-genome deep sequencing and bulk segregant analysis （Schneeberger et al., 2009; Abe et al., 2012）. Once the mapping population for a mutant is available, genetic analysis can be simplified by using the pool of F2 plants with mutant phenotype and the pool of those showing wild-type phenotype. Since most mutant phe- notypes are of qualitative character and follow simple inheritance patterns, genome-wide comparisons between the two DNA pools could localize the causal gene within a small genomic region. In most cases, the causative mutation （e.g., an in-frame indel） can be detected as well because there are only a limited number of sequence differences between the mutant and its wild-type. Hence, rapid mutant mapping via genomics ap- proaches is now becoming practical and cost-effective.

关键词： mutations available qualitative

Ant colonization increased total mercury but reduced methylmercury contents in boreal mires, Northeast China

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Journal of Environmental Sciences 2022年第9期34卷 50-58页

作者： Zhongsheng Zhang xuehui Zhang Yuan Xin Haitao Wu Northeast Institute of geography and Agroecology Chinese Academy of SciencesChangchun 130012China University of Chinese Academy of Sciences Beijing 100049China Shengyang University Shenyang 110044China

Soil macroinvertebrates as ecosystem engineers play significant, but largely ignored, roles in affecting mercury(Hg) cycle by altering soil physical-chemical properties. Ant is likely expanded into boreal mires with climate warming, however, its impacts on Hg cycle remained poorly understood. We compared total Hg(THg) and methylmercury(Me Hg) contents in soils from antmounds( Lasius flavus) and the nearby ambient in a boreal mire in Northeast China. The present work seeks to unravel factors that controlling Me Hg levels in case of ant appearance or absence. The average THg was 179 μg/kg in the ant mound and was 106.1 μg/kg in nearby soils, respectively. The average Me Hg was 10.9 μg/kg in the ant mound and was 12.9 μg/kg in nearby soils, respectively. The ratios of Me Hg to THg(%Me Hg) were 7.61% in ant mounds and 16.75% in nearby soils, respectively. Ant colonization caused THg enrichment and Me Hg depletion, and this change was obvious in the 10-20 cm depth soil layer where ants mainly inhabited. Spectrometry characteristics of soil dissolved organic matter(DOM) exert a stronger control than microorganisms on Me Hg variation in soils. A structural equation model revealed that the molecular weight of DOM inhibited Me Hg irrespective of ant presence or absence, while humification conducive to Me Hg significantly in ant mound soils. Microorganisms mainly affected Hg methylation by altering the molecular weight and humification of DOM. We propose that the effects of ant colonization on Me Hg rested on DOM feature variations caused by microorganisms in boreal mires.

关键词： Ant colonization Mercury Methylmercury Boreal mire DOM spectrometry

Ultrastrong and ductile BCC high-entropy alloys with low-density via dislocation regulation and nanoprecipitates

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Journal of Materials Science & Technology 2022年第15期110卷 109-116页

作者： xuehui Yan Peter K.Liaw Yong Zhang Beijing Advanced Innovation Center of Materials genome Engineering State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing 100083China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996United States of America

The high strength is a typical advantage of body-centered-cubic high-entropy alloys(BCC–HEAs).However,brittleness and weak strain-hardening ability are still their Achilles'***,extraordinary strength together with good tensile ductility are achieved in(Zr_(0.5)Ti_(0.35)Nb_(0.15))_(100-x)Al_(x) alloys(at.%,x=10 and 20)at room *** low densities of less than 6 g/cm^(3)are exhibited in these *** nanoprecipitates and diversifying dislocation motions are the keys to achieving such salient *** is worth noting that the tensile strength of 1.8 gPa in(Zr_(0.5)Ti_(0.35)Nb_(0.15))_(80)Al_(20)alloy is a record-high value known in reported BCC–HEAs,as well as a tensile strain over 8%.Furthermore,the maximum strain of~25%in(Zr_(0.5)Ti_(0.35)Nb_(0.15))_(90)Al_(10)alloy can challenge existing limit value,and is accompanied with a tensile strength of 1.2 *** current work does not only provide novel ultra-strong and tough structural materials with low density,but also sheds new light on designing BCC–HEAs with attractive performances and strain-hardening ability.

关键词： High-entropy alloys Mechanical properties Dislocation Nanoprecipitates Strain hardening

介孔La_(1-x)Sr_(x)MnO_(3)催化剂的COK-12纳米浇铸法制备

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硅酸盐通报 2024年第8期43卷 3079-3088页

作者：黄学辉胡祥奥陈文臻邓鹏辉武汉理工大学材料科学与工程学院武汉430070

钙钛矿型催化剂在汽车尾气净化方面具有良好的应用潜力。本文以表面活性剂P123为软模板剂,廉价的硅酸钠为硅源,在近中性条件下制备了介孔材料COK-12。并以此为基础,以对二甲苯为扩容剂对COK-12进行改性,得到了大孔径、有序的介孔材料。... 详细信息

钙钛矿型催化剂在汽车尾气净化方面具有良好的应用潜力。本文以表面活性剂P123为软模板剂,廉价的硅酸钠为硅源,在近中性条件下制备了介孔材料COK-12。并以此为基础,以对二甲苯为扩容剂对COK-12进行改性,得到了大孔径、有序的介孔材料。随后以改性介孔材料为模板剂,采用纳米浇铸法结合溶胶-凝胶法制备了介孔La_(0.8)Sr_(0.2)MnO_(3)催化剂。结果显示,在550℃下合成的催化剂具有较大的比表面积(72.11 m^(2)/g),表面Mn^(4+)/Mn^(3+)和O_(ads)/O_(lat)摩尔比最高。此外,样品的CO催化性能测试转化表明,550℃下合成的样品具有最好的催化活性和优秀的高温稳定性,其特征温度T_(50)和T_(90)分别为180和218℃。

关键词： COK-12 介孔材料纳米浇铸法溶胶-凝胶法 CO催化

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钛酸铝-堇青石复相陶瓷的制备和性能研究

硅酸盐通报 2024年第6期43卷 2241-2249页

作者：黄学辉陈文臻邓鹏辉胡祥奥武汉理工大学材料科学与工程学院武汉430070

本研究以MgO为稳定剂,以堇青石为增强剂,通过固相反应法成功制备了钛酸铝-堇青石复相陶瓷,并系统研究了MgO和堇青石以及烧结温度对复相陶瓷物相组成、显微结构、烧结性能和热力学性能的影响。结果表明,MgO的引入促进了钛酸铝晶粒的合成... 详细信息

本研究以MgO为稳定剂,以堇青石为增强剂,通过固相反应法成功制备了钛酸铝-堇青石复相陶瓷,并系统研究了MgO和堇青石以及烧结温度对复相陶瓷物相组成、显微结构、烧结性能和热力学性能的影响。结果表明,MgO的引入促进了钛酸铝晶粒的合成和长大,降低了烧结温度,并通过形成Mg_(x)Al_(2(1-x))Ti_((1+x))O_(5)固溶体提高了钛酸铝陶瓷的热稳定性。堇青石在烧结致密化和力学性能方面起着重要作用。在1325℃烧结条件下,MgO含量为8.00%、堇青石含量为15.00%的样品表现出良好的性能,体积密度为3.49 g/cm^(3),气孔率仅为2.2%,抗弯强度达到66.8 MPa,热膨胀系数为2.6×10^(-6)K^(-1)(室温至1000℃)。研究结果为设计和制备具备优异综合性能的高温结构陶瓷提供了新的思路。

关键词：钛酸铝堇青石复相陶瓷烧结温度抗弯强度热膨胀