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Microstructure evolution, mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

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Journal of Magnesium and Alloys 2024年第5期12卷 1944-1964页

作者： Guangyu Li wenming jiang Feng Guan Junwen Zhu Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology

In this paper, the effect of the Si content on microstructure evolution, mechanical properties, and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically. The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer（MRL）, whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites, while the hypereutectic Al-Si/AZ91D composites were opposite. The MRL included eutectic layer（E layer）,intermetallic compound layer（IMC layer） and transition region layer（T layer）. In the IMC layer, the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg2Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides, increasing Si content, the thickness proportion of the T layer increased, forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content, and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa, which was 73.4% higher than the Al-6Si/AZ91D composite. The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content. The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg2Si particle reinforcement, the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

关键词： Al/Mg bimetallic composites Si content Mg 2 Si reinforcement Microstructure Mechanical properties Fracture behavior

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Improving mechanical properties of AZ91D magnesium/A356 aluminum bimetal prepared by compound casting via a high velocity oxygen fuel sprayed Ni coating

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Journal of Magnesium and Alloys 2022年第4期10卷 1075-1085页

作者： Guangyu Li wenming jiang Feng Guan Junwen Zhu Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting.The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time.Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal.The 10μm’s Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds(IMCs)at the interface zone of the AZ91D/A356 bimetal,while the Ni coating with the thickness of 45μm and 190μm can avoid the formation of the Al-Mg IMCs.When the Ni coating was 45μm,the Ni coating disappeared and transformed into Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles at the interface zone.With a thickness of 190μm’s Ni coating,part of the Ni coating remained and the interface layer was composed of the Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles,Mg_(2)Ni layer,Ni solid solution(SS)layer,Al_(3)Ni_(2) layer,Al_(3)Ni layer and sporadic Al_(3)Ni+Al-Al_(3)Ni eutectic structures from AZ91D side to A356 side in sequence.The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs.The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45μm thickness enhanced 41.4%in comparison with that of the bimetal without Ni coating,and the fracture of the bimetal with 45μm’s Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.

关键词： Magnesium/aluminum bimetal Microstructure Mechanical properties Ni coating Compound casting High velocity oxygen fuel spraying

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Effect of La on microstructure,mechanical properties and fracture behavior of Al/Mg bimetallic interface manufactured by compound casting

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Journal of Materials Science & Technology 2022年第10期105卷 214-225页

作者： Zheng Zhang wenming jiang Guangyu Li Junlong Wang Feng Guan Guoliang Jie Zitian Fan State Key Laboratory of Materials Processing and Die and Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

To improve the Al/Mg bimetallic interface,La was added into the Al/Mg bimetallic interface manufactured by a compound casting process.The effect of La addition on the microstructure,mechanical properties and fracture behavior of the Al/Mg bimetallic interface and the formation mechanism of the interface were studied in detail.Al_(11)La_(3),Al_(8)Mn_(4)La,Al_(20)Ti_(2)La,and other rare earth precipitates(RE precipitates)preferentially precipitated at the interface with La addition,while the number of the Al_(11)La_(3)and Al_(8)Mn_(4)La located in eutectic structure area(E area)gradually increased and aggregated in the interface with the increase of the La content.Besides,the matrix structure in different areas of the Al/Mg interface changed in different degrees,and the eutectic structure and primaryγ(Mg_(17)Al_(12))dendrites in the E area were refned,but the intermetallic compounds area(IMC area)had no obvious change.With the addition of the La,the interface was strengthened under the comprehensive effect of refnement strengthening and precipitation strengthening from the E area.When the La content increased to 1.0%,the shear strength of the Al/Mg bimetal reached the maximum of 51.54 MPa,which was 30.95%higher than the group without La addition.However,with the further increase of the La content,the large area aggregation of the Al_(11)La_(3)and Al_(8)Mn_(4)La occurred in the interface,leading to the separation of the matrix structure of the E area and the decrease of the shear strength of the Al/Mg interface.

关键词： Compound casting Al-Mg intermetallic compounds Rare earth La Al/Mg interface Microstructure Mechanical properties

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Effect of vibration on interfacial microstructure and mechanical properties of Mg/Al bimetal prepared by a novel compound casting

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Journal of Magnesium and Alloys 2022年第8期10卷 2296-2309页

作者： Feng Guan wenming jiang Guangyu Li Junwen Zhu Junlong Wang Guoliang Jie Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.

关键词： Mg/Al bimetal Vibration Compound casting Interfacial microstructure Bonding properties

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Preparation, interfacial regulation and strengthening of Mg/Al bimetal fabricated by compound casting: A review

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Journal of Magnesium and Alloys 2023年第9期11卷 3059-3098页

作者： Guangyu Li wenming jiang Feng Guan Zheng Zhang Junlong Wang Yang Yu Zitian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Mg/Al bimetal combines the advantages of both aluminum and magnesium and has broad application prospects in automotive, aerospace,weapons, digital products and so on. The compound casting has the characteristics of low cost, easy to achieve metallurgical combination and suitable for the preparation of complex bimetallic parts. However, bimetallic joint strength is low due to differences of physical properties between Al and Mg, oxide film on metallic surface and interfacial Al-Mg IMCs, which is closely related to the interfacial microstructure and properties. Therefore, how to control the interface of the bimetal to achieve performance enhancement is the focus and difficulty in this field. At present, there are mainly the following strengthening methods. First, the “zincate galvanizing” and “electrolytic polishing+anodic oxidation” technology were exert on the surface of Al alloy to remove and break the oxide film, which improved the wettability between Al and Mg. Second, the undesirable Al-Mg IMCs were reduce or elimination by adding the interlayers(Zn, Ni and Ni-Cu). Thirdly, the evolution process of interfacial microstructure was changed and fine strengthening phases were formed by adding Si element to Al alloy or rare earth element to Mg alloy. Fourthly, mechanical vibration and ultrasonic vibration were applied in the process of the filling and solidification to refine and homogenize the interfacial structure. Finally, some other methods, including secondary rolling, thermal modification, heat treatment and constructing exterior 3D morphology, also can be used to regulate the interfacial microstructure and compositions. The above strengthening methods can be used alone or in combination to achieve bimetallic strengthening. Finally, the future development direction of the Mg/Al bimetal is prospected, which provides some new ideas for the development and application of the Mg/Al bimetal.

关键词： Mg/Al bimetal Preparation Compound casting Interfacial regulation Interface strengthening Research progress

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Novel technologies for the lost foam casting process

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Frontiers of Mechanical Engineering 2018年第1期13卷 37-47页

作者： wenming jiang Zitian FAN State Key Laboratory of Material Processing and Die & MouldTechnology Huazhong University of Science and Technology Wuhan430074 China

Lost foam casting （LFC） is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the A1 and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting techno- logy; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thin- wall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the A1/Mg and A1/A1 bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.

关键词： LFC under vacuum and low pressure vibra-tion solidification pressure solidification expendable shellcasting bimetallic castings

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Continued antigenic variation of highly pathogenic avian influenza A(H7N9)virus in laying hens in China,2020–2021

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Virologica Sinica 2022年第4期37卷 631-633页

作者： wenming jiang Xin Yin Shuo Liu Shaobo Liang Cheng Peng Guangyu Hou Jinping Li Xiaohui Yu Yang Li Jingjing Wang Hualei Liu China Animal Health and Epidemiology Center Qingdao266032China

Dear Editor,Since it first appeared in humans in China in 2013,a novel H7N9influenza virus has caused 1,568 cases of infection,with a mortality rate of 39.2%(Yin et al.,2021).The early H7N9 virus strains had low pathogenicity and did not cause avian disease(Zhang et al.,2013).However,they caused concern about poultry consumption and caused huge economic losses to the poultry industry.Since mid-2016,some H7N9 viruses mutated.

关键词： H7N9 influenza

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制造景观:项目经营下的乡村建设

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华中农业大学学报（社会科学版） 2024年第3期 190-201页

作者：刘江张文明华东师范大学社会发展学院上海200241

项目下乡中的经营行为引发了景观化建设现象,研究以湖北T村为例,从空间实践、生产机制和治理效应三方面对此展开分析。从景观化的空间实践来看,T村在项目试点中的密集投入和差异化建设,导致景观密集生产和村庄空间分化,并凸显了景观的... 详细信息

项目下乡中的经营行为引发了景观化建设现象,研究以湖北T村为例,从空间实践、生产机制和治理效应三方面对此展开分析。从景观化的空间实践来看,T村在项目试点中的密集投入和差异化建设,导致景观密集生产和村庄空间分化,并凸显了景观的工具价值。从景观化的生产机制来看,主要源于对项目的经营。在决策层面,省级政府以行政发包配合项目下发,容易导致资源堆砌和重复试点;在下发过程中,县乡政府缺少代理人,强化了项目的集中下发冲动;在执行层面,项目捆绑产生了较强的执行压力,导致目标对照基础上的空间营造。从景观化的治理效应来看,一方面有利于空间更新、基础设施改善和组织权威强化,另一方面又导致景观的后续养护难题、对生活景观的排斥、对村民生计的影响以及村民隔阂等。这种好坏参半的治理效应体现了“项目悬浮”问题,即项目与村民需求脱节。最后,研究还提出了基层社会从“经营项目”向“经营空间”的延伸。

关键词：景观化建设经营项目美丽乡村新代理人经营空间

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N~6-甲基腺嘌呤修饰及其调控因子在男性生殖中的作用

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四川大学学报（医学版） 2024年第3期55卷 527-534页

作者：蒋婷张学广许文明四川大学华西第二医院生殖遗传与表观遗传调控研究室成都610041 出生缺陷与相关妇儿疾病教育部重点实验室(四川大学) 成都610041

在哺乳动物中,精子发生是一个高度复杂且协调的生殖细胞分化过程,这一过程受到转录、转录后和翻译水平的精确调控,以确保不同发育阶段的生精细胞正确表达特定基因并维持正常的生精过程。N~6-甲基腺嘌呤(N~6-methyladenosine,m~6A)是真... 详细信息

在哺乳动物中,精子发生是一个高度复杂且协调的生殖细胞分化过程,这一过程受到转录、转录后和翻译水平的精确调控,以确保不同发育阶段的生精细胞正确表达特定基因并维持正常的生精过程。N~6-甲基腺嘌呤(N~6-methyladenosine,m~6A)是真核生物m RNA上最丰富的修饰,在诸如m RNA剪接、转运和翻译等多个生物过程发挥关键作用。RNA甲基化修饰是一个动态可逆的过程,主要通过编码器(writers)催化、消码器(erasers)去除和读码器(readers)识别来调控修饰水平。本文首先概述了精子发生的主要阶段,然后重点介绍m~6A修饰及相关蛋白在雄性生殖细胞不同发育阶段的关键功能,最后简要总结了目前检测m~6A的主要方法,以期深入了解RNA修饰在调控精子发生以及在男性不育中发挥的作用和机制。

关键词：精子发生 N~6-甲基腺嘌呤 RNA修饰男性不育表观遗传学综述

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“钟摆逻辑”:有限结构化的村务工作模式——基于湖北S村的经验研究

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地方治理研究 2024年第2期 65-77,M0004页

作者：张文明刘江华东师范大学社会发展学院上海200241

我国村级组织具有复杂性,在村务工作的组织模式、规范要求和具体内容等层面存在较大差异。研究发现,基层的村务工作呈现出明显的“钟摆逻辑”,即面对常规任务和特殊任务采取不同的应对方式。在处理常规任务时,运用分工合作的模式,将任... 详细信息

我国村级组织具有复杂性,在村务工作的组织模式、规范要求和具体内容等层面存在较大差异。研究发现,基层的村务工作呈现出明显的“钟摆逻辑”,即面对常规任务和特殊任务采取不同的应对方式。在处理常规任务时,运用分工合作的模式,将任务进行条线分割,主要采用坐班制、固定工作场所及规则治理等手段;而面对特殊任务时,则结成“行动班子”,以团结合作、工作动员等方式来应对。这种在常态模式与动员模式之间的切换使得村务工作处于有限结构化的状态,有助于提升基层治理效能。

关键词：乡村治理钟摆逻辑村务工作有限结构化分工合作体任务共同体

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