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Twin-twin geometric structure effect on the twinning behavior of an Mg-4Y-3Nd-2Sm-0.5Zr alloy traced by quasi-in-situ EBSD

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Journal of Magnesium and Alloys 2023年第4期11卷 1381-1392页

作者： Yunwei Gui quanan li Yibei Xue lingxiao Ouyang School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Provincial and Ministerial Co-construction of Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology Luoyang 471023China Department of Materials Processing Graduate School of EngineeringTohoku University6-6-11 AobaAramakiAoba-kuSendai 980-8579Japan School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’an 710072China

We studied the microstructure evolution of Mg-4Y-3Nd-2Sm-0.5Zr alloy by quasi-in-situ electron backscatter diffraction(EBSD)along with several strains under compression tests,which provided direct evidence for the influence of different twin-twin geometric structure on the twinning behavior.The results showed that the mechanical properties of the alloy were higher than traditional magnesium alloys(the maximum compressive strength reaches 402.5 MPa)due to the strengthening effect of Sm and Nd elements addition on solution strengthening,precipitation strengthening,and grain refinement.Combined with the quasi-in-situ EBSD technique,two different twin-twin geometric structures,‘parallel structure’and‘cross structure’,were observed directly in the alloy.In the later stage of deformation,for‘parallel structure’,residual stress and a large number of dislocations mainly existed in the twin boundary and tip position.For the‘cross structure’,there was a lot of dislocation density in the interior of twins after fusion.The twin growth rate of‘parallel structure’was much faster than that of‘cross structure’because the stress of twins was mainly concentrated on the tip of twin.When the movement for the tip of twin was blocked,the growth rate of twin would be obviously decreased.Moreover,the‘cross structure’was easy to produce closed space.Due to the constraints of surrounding twins,the confined space was easy to stress concentration,thus inhibiting the growth of twins.At the same time,the‘cross structure’of twins needed a more external force to continue to deform,which also served as a strengthening structure.

关键词： Mg-RE alloy Mechanical testing Twinning Quasi-in-situ EBSD

Effect of thermo-mechanical processing parameters on the dynamic restoration mechanism in an Mg-4Y-2Nd-1Sm-0.5Zr alloy during hot compression

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Journal of Materials Science & Technology 2021年第31期90卷 205-224页

作者： Yunwei Gui lingxiao Ouyang Yibei Xue quanan li School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Provincial and Ministerial Co-construction of Collaborative Innovation Center for Non-ferrous Metal New Materials and Advanced Processing Technology Luoyang 471023China Department of Materials Processing Graduate School of EngineeringTohoku University6-6-11 AobaAramakiAoba-kuSendai980-8579Japan School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’an 710072China

Microstructure evolution and dynamic restoration mechanism of solution-treated Mg-4Y-2Nd-1Sm-0.5Zr alloy have been studied under three TMP parameters consisting of deformation temperatures(350-500℃),strain rates(0.01-5 s^(-1)),and strains(0.2,0.4,and 0.8).A strong dynamic softening is observed in all stress-strain curves,even at higher strain rates(1 and 5 s^(-1))due to an adiabatic heating effect.Various stress-strain curves are applied to construct a processing map and develop an Arrhenius-type constitutive equation.With the prediction of the processing map,an optimal processing domain has been determined to be the temperature range 450-500℃and strain rate range 0.01-0.1 s^(-1)at a strain of 0.8.The volume fraction of DRX grains is the largest in the corresponding domain of high temperature and low strain rate.For the effect of TMP parameters on the dynamic restoration,the discontinuous dynamic recrystallization(DDRX)and continuous DRX(CDRX)synergistic effect occur throughout the whole process at high temperature and high strain rate.In terms of high temperature and low strain rate,DDRX characteristics at a low strain and then the DDRX+CDRX synergistic effect is observed at a higher strain.Although the DRX process is weak at low temperature and low strain rate,deformation twins have occurred and provided nucleation sites for DRX grains.

关键词： Mg-RE alloy TMP parameters Processing map prediction Constitutive analysis Dynamic restoration mechanism

Microstructure and mechanical properties of Mg-Gd-Y-Sm-Al alloy and analysis of grain refinement and strengthening mechanism

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Journal of Rare Earths 2019年第12期37卷 1351-1358页

作者： Xiaoya Chen quanan li Jun Chen limin Zhu School of Materials Science and Engineering Xi'an University of TechnologyXi'an 740048China School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Collaborative Innovation Center of Nonferrous Metals Henan ProvinceLuoyang 471023China

The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and high resolution transmission electron microscopy.Based on the theory of edge—edge matching and electronegativity theory,the mechanism of grain refinement is discussed.The strengthening mechanism is expounded conveniently from fine grain strengthening,coherent strengthening,precipitation strengthening and grain boundary strengthening.The results show that the micro structure of Mg-11 Gd-2 Y-0.6 Al alloy is mainly composed of a-Mg matrix,Mg5 Gd and Mg24Y5 phases.The addition of Sm forms Mg41Sm5 phase in the alloy and refines the alloy.The addition of Sm significantly improves the mechanical properties of the alloy at room and high temperatures.When the addition of Sm is 3 wt%,the tensile strengths of the alloy at room temperature and high temperature(200℃)reach the maximum value 292 and 321 MPa,respectively.The fracture mode of the alloy at different temperatures is mainly brittle fracture and intercrystalline fracture.

关键词： Mg-11Gd-2Y-0.6Al alloy Micro structure Mechanical property Grain refinement Strengthening mechanism Rare earths

Role of slip and {10-12} twin on the crystal plasticity in Mg-RE alloy during deformation process at room temperature

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Journal of Materials Science & Technology 2021年第21期80卷 279-296页

作者： Yunwei Gui Yujie Cui Huakang Bian quanan li lingxiao Ouyang Akihiko Chiba Department of Materials Processing Graduate School of EngineeringTohoku University6-6-11 AobaAramakiAoba-kuSendai980-8579Japan Institute for Materials Research Tohoku University2-1-1 KatahiraAoba-kuSendai980-8577Japan School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang471023China Collaborative Innovation Center of Nonferrous Metals Henan ProvinceLuoyang471023China

The deformation mechanism of slips and twins has a considerable influence on the plasticity of magnesium alloys. However, the roles of slips and twins in the room-temperature deformation of Mg-rare earth(Mg-RE) alloys with high contents of rare earth elements is rarely investigated. Here, the microstructural evolution and deformation mechanism of an aged Mg-5 Y-2 Nd-3 Sm-0.5 Zr alloy during uniaxial compression at room temperature were systematically investigated using in-situ electron-backscattered diffraction and transmission electron microscopy. The results indicated that in the early stage of deformation, the Mg-RE alloy was mainly controlled by the slip of dislocations in the basal plane and the coordinated c-axis strain of the {10-12} twin. With an increase in the strain, the grain orientation became more suitable for the initiation of pyramidal Ⅱ dislocations in the later stage of deformation;these dominated the deformation mechanism. In the twin evolution of the Mg-RE alloy, there were three types of twin-twin interaction behaviors:(i) single twin variant 'parallel' structure,(ii) single twin variant 'cross' structure, and(iii) multi twin variant 'cross' structure. In addition, three types of twin-grain boundary interaction behaviors were summarized:(i) twin 'refracting through' grain boundary,(ii) twin'parallel through' grain boundary, and(iii) twin 'fusing through' grain boundary, which are expected to act as new means and solutions for the twin strengthening of magnesium alloys.

关键词： Mg-RE alloy Crystal plasticity In-situ EBSD Dislocation Twinning

Grain refinement and weak-textured structures based on the dynamic recrystallization of Mg–9.80Gd–3.78Y–1.12Sm–0.48Zr alloy

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Journal of Magnesium and Alloys 2021年第2期9卷 456-466页

作者： Yunwei Gui lingxiao Ouyang Yujie Cui Huakang Bian quanan li Akihiko Chiba Department of Materials Processing Graduate School of EngineeringTohoku University6-6-11 AobaAramakiAoba-kuSendai 980-8579Japan Institute for Materials Research Tohoku University2-1-1 KatahiraAoba-kuSendai 980-8577Japan School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China Collaborative Innovation Center of Nonferrous Metals Henan ProvinceLuoyang 471023China

We utilized electron backscatter diffraction to investigate the microstructure evolutions of a newly developed magnesium-rare earth alloy(Mg–9.80 Gd–3.78 Y–1.12 Sm–0.48 Zr)during instantaneous hot indirect extrusion.An equiaxed fine-grained(average grain size of 3.4±0.2μm)microstructure with a weak texture was obtained.The grain refinement was mainly attributed to the discontinuous dynamic recrystallization(DDRX)and continuous DRX(CDRX)processes during the hot indirect extrusion process.The twin boundaries formed during the initial deformation stage effectively increased the number of high angle grain boundaries(HAGBs),which provided sites for new grain nuclei,and hence,resulted in an improved DDRX process.Along with DDRX,CDRX processes characterized by low angle grain boundary(LAGB)networks were also observed in the grain interior due to effective dynamic recovery(DRV)at a relatively high temperature of 773 K and high strain rates.Thereafter,LAGB networks were transformed into HAGB networks by the progressive rotation of subgrains during the CDRX process.

关键词： Magnesium-rare earth(Mg-Re)alloy Grain refinement Discontinuous dynamic recrystallization(DDRX) Continuous dynamic recrystallization(CDRX) Hot indirect extrusion

Mn^(4+)激活氟化物红色荧光粉的制备与表面改性研究进展

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功能材料 2024年第6期55卷 6044-6052页

作者：王晓赵豫洁李全安陈晓亚河南科技大学材料科学与工程学院河南洛阳471023 河南科技大学物理工程学院河南洛阳471023 有色金属新材料与先进加工技术省部共建协同创新中心河南洛阳471023 龙门实验室河南洛阳471000

白光发光二极管因其节能、环保、高效等特性,在照明和显示等领域具有广泛的应用。一直以来,获得具有低色温(CCT=2700~4500 K)、高显色指数(CRI,R_(a)>80)、节约成本且适宜人眼的暖白光发光二极管是该领域研究者不懈的追求。其中红色荧... 详细信息

白光发光二极管因其节能、环保、高效等特性,在照明和显示等领域具有广泛的应用。一直以来,获得具有低色温(CCT=2700~4500 K)、高显色指数(CRI,R_(a)>80)、节约成本且适宜人眼的暖白光发光二极管是该领域研究者不懈的追求。其中红色荧光粉在高显色性能荧光粉转换型白光发光二极管器件中发挥重大作用,其研究与开发具有重要意义。概述了近年来Mn^(4+)掺杂氟化物红色荧光粉的研究进展,主要介绍了该类荧光粉材料的常规和绿色制备方法,针对Mn^(4+)掺杂氟化物红色荧光粉耐湿性能较差的特点,对其改性的相关报道进行了总结归纳。最后,对此类荧光粉所面临的问题进行了分析展望。

关键词：红色荧光粉 Mn^(4+)掺杂氟化物合成方法稳定性

苏拉威西海海面高度多频率季节内变化及其机制分析

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海洋学报 2024年第2期46卷 14-27页

作者：毛志榜王露李君益谢玲玲郑全安广东海洋大学海洋与气象学院广东湛江524088 陆架及深远海气候、资源与环境广东省高等学校重点实验室广东湛江524088 自然资源部空间海洋遥感与应用重点实验室北京100081 海军士官学校航海系安徽蚌埠233012 美国马里兰大学大气与海洋科学系马里兰州大学市20742

本文利用1993-2022年卫星高度计观测数据,分析苏拉威西海海面高度多频率季节内变化信号的时空特征,利用罗斯贝标准模理论给出动力解释。谱分析显示,苏拉威西海海面高度变化存在很强的30~90 d的季节内信号,其平均功率谱密度为半年内信号... 详细信息

本文利用1993-2022年卫星高度计观测数据,分析苏拉威西海海面高度多频率季节内变化信号的时空特征,利用罗斯贝标准模理论给出动力解释。谱分析显示,苏拉威西海海面高度变化存在很强的30~90 d的季节内信号,其平均功率谱密度为半年内信号平均功率谱密度的13倍。这些季节内信号具有离散、不连续的谱峰周期,其中54.0 d和64.4 d的峰值最大,分别为30~90 d信号平均谱值的28倍和23倍。罗斯贝标准模态理论分析显示,近封闭的苏拉威西深海盆存在离散的罗斯贝标准模态。卫星高度计观测的季节内变化与罗斯贝标准模态结果的二维空间结构演化、周期以及西传速度一致,罗斯贝标准模态解的叠加呈现出与海面高度变化相似的方差分布,这说明苏拉威西海海盆的固有振荡是其季节内变化特征形成的重要机制之一。

关键词：苏拉威西海多频率季节内变化时空特征罗斯贝标准模态固有振荡

Unusual coastal ocean cooling in the northern South China Sea by a katabatic cold jet associated with Typhoon Mujigea(2015)

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Acta Oceanologica Sinica 2019年第5期38卷 62-75页

作者： Yuxin Shi lingling Xie quanan Zheng Shuwen Zhang Mingming li Junyi li Guangdong Key Laboratory of Coastal Ocean Variation and Disaster Prediction Guangdong Ocean University Department of Atmospheric and Oceanic Science University of Maryland

This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event.

关键词： Typhoon Mujigea(2015) second-round cooling katabatic cold jet South China Sea westerly wind front

A case study of a Kuroshio main path cut-off event and impacts on the South China Sea in fall-winter 2013–2014

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Acta Oceanologica Sinica 2019年第4期38卷 12-19页

作者： quanan Zheng Chung-Ru Ho lingling Xie Mingming li Department of Atmospheric and Oceanic Science University of Maryland Guangdong Key Laboratory of Coastal Ocean Variability and Disaster Prediction Guangdong Ocean University Department of Marine Environmental Informatics National Taiwan Ocean University

This study examines a Kuroshio main path(KMP) cut-off event east of Taiwan Island occurred in fall-winter2013–2014 and its impacts on the South China Sea(SCS) by analyzing satellite altimetry and mooring observations. Satellite altimeter sea level anomaly(SLA) images reveal a complete process that a huge cyclonic eddy(CE) from the Pacific collided with the Kuroshio and the western boundary from 15 October 2013 to 15 January 2014. Mooring observations evidenced that the Kuroshio upper ocean volume transport was cut off more than 82% from 17×106 m^3/s in September to 3×106 m^3/s in November 2013. The KMP cut-off event caused the Kuroshio branching and intruding into the SCS and strengthened the eddy kinetic energy in the northern SCS west of the Luzon Strait. Using the total momentum as a dynamic criterion to determine the role of eddy collision with the Kuroshio reasonably explains the KMP cut-off event.

关键词： KMP cut-off event eddy kinetic energy dynamic criterion South China Sea