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Identifying the crystal structure of T 1 precipitates in Al-Li-Cu alloys by ab initio calculations and haadf-stem imaging

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Journal of Materials Science & Technology 2023年第2期133卷 41-57页

作者： Shuo Wang Xianghai Yang Junsheng Wang Chi Zhang Chengpeng Xue School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China

Controversial experimental reports on the crystal structure of T 1 precipitates in Al-Li-Cu alloys have ex-isted for a long time,and all of them can be classified into five *** clarify its ground-state atomic structure,herein,we have combined high-throughput first-principles calculations and CALPHAD,as well as aberration-corrected haadf-stem *** the special quasi-random structure(SQS)and supercell approximation(SPA)methods to simulate the local disorder on Al-Cu sub-lattices,we find that none of the present models can satisfy the phase stability in Al-Li-Cu ternary system based on temperature-dependent convex hull *** the cluster expansion(CE)formulas,structural predic-tions derived from the five-frame models were ***,by introducing the vibrational contribution to the free energy at aging temperatures,we proposed a novel ground-state T 1 structure that maintains a coherent relationship with Al-matrix at theAl *** underlying phase transition between the variants of T 1 precipitates was further *** means of ab initio molecular dynamics(AIMD)simulations,we resolved the controversy regarding the number of atomic layers con-stituting the T 1 phase and acknowledged the existence of Al-Li corrugated *** root cause of this structural distortion is triggered by atomic forces and *** work can have an positive impact on the novel fourth generation of Al-Cu-Li alloy designs by engineering the T 1 strengthening phase.

关键词： Al-Cu-Li alloys T 1 precipitates Cluster expansion First-principle calculations ab initio molecular dynamics haadf-stem

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Mg-Bi合金时效强化微结构的haadf-stem分析

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热加工工艺 2019年第8期48卷 203-205页

作者：董宇孙永辉邓江宁孙本哲谭俊东北大学新材料技术研究院辽宁沈阳110819 东北大学材料科学与工程学院辽宁沈阳110819

Mg-Bi合金经熔炼、均匀化及固溶处理、不同时间(2、16、200 h)时效强化处理后,使用高角度环形暗场扫描透射(haadf-stem)成像技术,研究了不同时效时间Mg-Bi合金中强化相的形态、大小、晶体结构和取向关系。结果表明,Mg-Bi合金在200℃时效... 详细信息

Mg-Bi合金经熔炼、均匀化及固溶处理、不同时间(2、16、200 h)时效强化处理后,使用高角度环形暗场扫描透射(haadf-stem)成像技术,研究了不同时效时间Mg-Bi合金中强化相的形态、大小、晶体结构和取向关系。结果表明,Mg-Bi合金在200℃时效2 h即可达到峰时效效果,唯一的时效强化相为α-Mg_3Bi_2相,与基体为共格析出关系,取向关系为:[1120]Mg_3Bi_2/[0001]Mg、(1110)Mg_3Bi_2/(1100)Mg或[1120]Mg_3Bi_2/[1120]Mg、(0003)Mg_3Bi_2/(1101)Mg。对试样进一步时效16 h和200 h后,微结构保持不变,表明Mg-Bi合金具有高温持久性和较好的抗蠕变性能,具有良好的应用前景。

关键词： Mg-Bi合金 haadf-stem 时效强化析出相

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狭缝阵列法产生准贝塞尔电子束用于haadf-stem成像研究

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电子显微学报 2024年第6期43卷 670-676页

作者：林宇铖陈鑫铠张婉如田鹤浙江大学电子显微镜中心硅材料国家重点实验室材料科学与工程学院浙江杭州310027

贝塞尔电子束具有的自愈性和无衍射性使其在电子显微成像和电子断层扫描等领域中具有独特优势。本文制备了狭缝阵列光阑并安装在透射电子显微镜中用于产生具有自愈性和无衍射性的准贝塞尔电子束(Bessel beams,BBs)。与单狭缝法相比,狭... 详细信息

贝塞尔电子束具有的自愈性和无衍射性使其在电子显微成像和电子断层扫描等领域中具有独特优势。本文制备了狭缝阵列光阑并安装在透射电子显微镜中用于产生具有自愈性和无衍射性的准贝塞尔电子束(Bessel beams,BBs)。与单狭缝法相比,狭缝阵列光阑(slit arrays aperture,SAA)法提高了BBs的中心束强度并降低衍射旁瓣影响。与普通会聚束相比,BBs被用于扫描透射模式(scanning transmission electron microscopy,stem)下的高角环形暗场像(high-angle annular dark-field,haadf),成像时具有更大景深并能修正强度与厚度间的非线性阻尼效应,因而BBs将在易损伤样品拍摄和电子断层扫描中拥有较好的应用前景。

关键词：狭缝阵列光阑贝塞尔电子束 haadf-stem

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时效处理Mg-La合金微结构的haadf-stem研究

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山西冶金 2024年第10期47卷 6-8页

作者：谭俊李顺洪黄启元东北大学分析测试中心辽宁沈阳110819 辽宁装备制造职业技术学院汽车工程学院辽宁沈阳110161 东北大学材料科学与工程学院辽宁沈阳110819

采用高角度环形暗场扫描透射电镜(haadf-stem)研究了Mg-3.0La合金的时效处理过程微结构序列演变规律。结果表明,经200℃时效处理后,随着时间推移,Mg-3.0La合金逐步出现La富集区域、富La的FCC析出相,且该析出相尺寸逐渐长大。Mg-3.0La合... 详细信息

采用高角度环形暗场扫描透射电镜(haadf-stem)研究了Mg-3.0La合金的时效处理过程微结构序列演变规律。结果表明,经200℃时效处理后,随着时间推移,Mg-3.0La合金逐步出现La富集区域、富La的FCC析出相,且该析出相尺寸逐渐长大。Mg-3.0La合金具有明显的时效强化效果,富La的FCC析出相在晶内和晶界上均有分布。

关键词： Mg-La合金 haadf-stem 微结构时效强化

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β-Mg5Gd平衡相原子尺度的haadf-stem表征

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中国体视学与图像分析 2019年第2期24卷 91-97页

作者：谢红波潘虎成任玉平李洪晓蒋敏秦高梧东北大学材料科学与工程学院材料各向异性与织构教育部重点实验室沈阳110819

本论文使用球差校正的高角环形暗场扫描透射电镜(Aberration-Corrected High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy,haadf-stem)结合选区电子衍射(Selected Area Electron Diffraction,SAED)技术系统表征了Mg-19.6 wt.%Gd合金300℃等温时效100 h后的时效析出行为。研究结果表明,Mg-19.6 Gd合金时效后期析出的平衡相为β-Mg5Gd。β-Mg5Gd相为fcc结构(空间群:■;晶格参数:a=22.34?),呈透镜状。β-Mg5Gd相具有一个■的惯习面,它们沿■3个方向均匀分布。β-Mg5Gd相在β1-Mg3Gd中形核,并由内而外生长取代β1相。β相与β1,以及与α-Mg基体都是完全共格的,其与β1相、基体的取向关系为[110]β//[110]β1//[0001]α;■。

关键词：镁合金时效析出 β相平衡相 haadf-stem

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基于haadf-stem方法研究电子在多层石墨烯中的散射

基于HAADF-STEM方法研究电子在多层石墨烯中的散射

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第十六届全国原子与分子物理学术会议

作者：丁望峰陈太师廖开明贺龙兵宋凤麒万建国周剑峰王广厚韩民南京大学固体微结构物理国家重点实验室

高角度散射暗场电子透射显微法(haadf-stem)在测量三维纳米结构中具有原子级的分辨能力。如果已知材料中的电子散射截面(Ω)或平均自由程(L),单个原子的计数就可以实现。但是电子散射是一个复杂的过程,散射常数(Ω或L)的第一性原理计算... 详细信息

高角度散射暗场电子透射显微法(haadf-stem)在测量三维纳米结构中具有原子级的分辨能力。如果已知材料中的电子散射截面(Ω)或平均自由程(L),单个原子的计数就可以实现。但是电子散射是一个复杂的过程,散射常数(Ω或L)的第一性原理计算还存在很大争论,

关键词：多层石墨烯 haadf-stem 电子散射

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Rotational and translational domains of beta precipitate in aged binary Mg-Ce alloys

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Journal of Magnesium and Alloys 2021年第3期9卷 1039-1056页

作者： B.Z.Sun H.X.Zhang Y.Dong J.X.Ren Y.Tian G.M.Xie J.Tan Y.H.Sun Na Xiao School of Materials Science and Engineering Northeastern UniversityShenyang 110819China State Key Lab Rolling&Automat Northeastern UniversityShenyang 110819China Key Laboratory for Anisotropy and Texture of Materials Ministry of EducationNortheastern UniversityShenyang 110819China Analytical and Testing Center Northeastern UniversityShenyang 110819China

The structural evolution fromβ_(1)(Mg_(3)Ce)toβ(Mg_(12)Ce)precipitates,which takes place at the over-aged stage of binary Mg-Ce alloys,are investigated by high-angle annular dark-field scanning transmission electron *** structural transformation mainly occurs in the{111}_(β1)crystallographic planes,where the newly formedβlattices exhibit two categories of domain structures,namely rotational and translational *** rotational domain is composed of threeβdomains(β_(RA),β_(RB)andβ_(RC)),which are related by a 120°rotation with respect to each other around the 111_(β1)axis of theirβ_(1)parent ***{111}_(β1)crystallographic planes can provide four sets of sublattices with the same orientation for an initial nucleation ofβ*** leads to the formation of four translationalβdomains(β_(TA),β_(TB),β_(TC)andβ_(TD)),among which any two differ by a vector of 1/6112_(β1).We deduce theoretically that there exist twenty-fourβdomains during this ***,considering the interfacial misfit,only one-third of domains can grow up and eventually formsβ***,a majority ofβribbons overlap partiallyβ_(1)plate,which is beneficial to relax interfacial strain amongβ,β_(1)andα-Mg matrix(α/β/β_(1)).The configuration of multipleβdomains can effectively regulate interfacial misfit ofα/βandβ/β_(1),which are responsible for enhancing the hardness and strength of Mg-Ce ***,this study aims to provide some clues to improve the over-aged performance of magnesium alloys by constructingβdomains and optimizing theα/β/β_(1)interface.

关键词： Magnesium alloys haadf-stem Rotational domain Translational domain Phase transition Interfacial misfit

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Formation and growth of precipitates in a Mg-7Gd-5Y-1Nd-2Zn-0.5Zr alloy aged at 200℃

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Journal of Magnesium and Alloys 2023年第7期11卷 2326-2339页

作者： Zhiwei Du Yonggang Peng Hang Teng Zhong Cao Kui Zhang Minglong Ma Xiaolei Han Ting Li Cong Che Yongjun Li Guobiao(Beijing)Testing&Certification Co. Ltd.Beijing 100088China China United Test&Certification Co. Ltd.Beijing 100088China Nanjing Yunhai Special Metal Co. Ltd.Nanjing 211212China Shanghai Spaceflight Precision Machinery Institute Shanghai 201600China State Key Laboratory of Non-Ferrous Metals&Processes GRIMAT Engineering Institute Co.Ltd.Beijing 101407China

Crystal structures,growth characteristics,and transformation of the precipitates in a Mg-7Gd-5Y-1Nd-2Zn-0.5Zr(wt.%)alloy aged at 200℃for various durations were investigated using transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(haadf-stem).A detailed Mg-Gd type precipitation sequence for Mg-Gd-Y-Nd-Zn alloys was proposed as follows:supersaturated solid solution→solute clusters→zigzag GP zones+β''(I)→β'→β'+protrusions/joints→pre-β_(1)→β_(1)→β.Solute clusters formed in the early stage of aging consisted of one or more rare-earth(RE)/Zn-rich atomic columns with different ***/Zn-rich solute clusters grew into zigzag GP zones andβ''(I)as aging time *** paired-zigzag GP zones might grow up to beβ'precipitates *** the peak-and plat-aging stages,the number of solute clusters in the matrix decreased until they disappeared,and most existed as zigzag arrays and super *** formed at the end ofβ'at an angle of 120°,then grew into joints when two differentβ'variants encountered ***/joints comprise zigzag arrays,super-hexagons,β'F,β''(II),β_(T),and hybrid structures rich in solute atoms,and act as catalysts for the growth of theβ'***β'grow by joints consumption while smallerβ'precipitates dissolve to form joints.β_(1)precipitates essentially evolve from pre-β_(1)precipitates,with four-point diamond structures formed by RE/Zn atomic substitution and atomic migration based on the originalα-Mg structure.

关键词： Magnesium alloys Aging Precipitates Microstructures haadf-stem

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Break the strength-ductility trade-off in a transformation-induced plasticity high-entropy alloy reinforced with precipitation strengthening

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Journal of Materials Science & Technology 2022年第13期108卷 125-132页

作者： Dong Huang Yanxin Zhuang Key Laboratory of Electromagnetic Processing of Materials(Ministry of Education) Northeastern UniversityShenyang110819China

Transformation-induced plasticity(TRIP)endows material with continuous work hardening ability,which is considered as a powerful weapon to break the strength-ductility ***,FCC based alloys with TRIP effect can not get rid of the“soft”feature of the structure entirely,resulting in insufficient yield ***,a Co_(x)Cr_(25)(AlFeNi)_(75-x) high-entropy alloy is *** phase is used as strengthening component to improve yield strength,while TRIP effect ensures *** with the previous TRIP high-entropy alloy,its yield strength is nearly doubled,and the uniform elongation is more than 55%at room ***,the corresponding multiphase microstructure evolution and deformation mechanisms are ***,stacking faults andΣ3 twin boundaries are confirmed to be the nucleation sites of HCP phase by *** composition design and proper heat treatment process make it a perfect combination of precipitation strengthening and transformationinduced plasticity,and thus guide design in the high-performance alloy.

关键词： High-entropy alloys Transformation-induced plasticity Precipitation strengthening Nucleation site haadf-stem

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Precipitation on stacking faults in Mg–9.8wt%Sn alloy

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Journal of Materials Science & Technology 2020年第10期42卷 230-240页

作者： C.Q.Liu C.He H.W.Chen J.F.Nie International Joint Laboratory for Light Alloys(Ministry of Education) College of Materials Science and EngineeringChongqing UniversityChongqing400044China Department of Materials Science and Engineering Monash UniversityVictoria3800Australia Electron Microscopy Center Chongqing UniversityChongqing400044PR China

In this work,we have systematically investigated precipitation ofβ’-Mg3Sn phase on intrinsic stacking faults I1 and I2 in a Mg-9.8 wt%Sn alloy using aberration-corrected scanning transmission electron *** observed I1 faults are generated by the dissociation of c+a perfect dislocations and bounded by Frank partial dislocations having a Shockley *** ofβ’on I1 involves a shear of 1/3α,similar to its formation directly from theα-Mg ***β’phase often nucleates at one end of an I1 fault due to the interaction between shear strain fields ofβ’and the Shockley component of the Frank partial at that end,and subsequently grows towards the other end of the *** theβ’reaches to the other end,the Shockley partial bounding the lengthening end of theβ’reacts with the Frank partial bounding the fault,generating an a perfect dislocation that can glide away from the precipitate and the *** observed I2 faults are generated by the dissociation of a perfect dislocations and bounded by Shockley *** ofβ’on I2 does not need a shear of 1/3α,since the pre-existing I2 fault already provides an ABCA four-layer structure ofβ’.Thickening of theβ’that has already formed on the I2 involves the successive occurrence of three crystallographically equivalent shears of 1/3αon every second(0002)αplane of theα-Mg *** this thickening mechanism is similar to that of theβ’formed directly from theα-Mg matrix,an a perfect dislocation will be produced when theβ’is thickened to eight layers,and it can again glide away from the precipitate and the fault.

关键词： Heterogeneous precipitation haadf-stem Shockley partial dislocation Frank partial dislocation Dislocation reaction

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