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Microstructures and mechanical properties of laser-directed energy deposited CrCoNi medium-entropy alloy

Rare Metals 2024年第7期43卷 3286-3300页

作者： Wen-Jie Zhao Chang-Yu Liu Peng-Cheng Che Zhi-Liang Ning Hong-Bo Fan Jian-Fei Sun yong-jiang huang Alfonso H.W.Ngan National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of Technology Space Environment Simulation Research Infrastructure Harbin Institute of Technology Department of Mechanical Engineering The University of Hong Kong

The distinctive intrinsic heat treatment(IHT)originating from cyclic reheating in the laser-directed energy deposition(LDED) has attracted growing attention in recent years.In this investigation,simulations and experimental characterizations were performed to examine the impact of IHT on the micros true ture and mechanical properties of LDED-fabricated CrCoNi medium-entropy alloy(MEA).The results show that the intensity of the IHT is proportional to the utilized laser energy density(LED).As the LED increased,significant dynamic recrystallization and grain refinement occurred within the alloy due to the enhanced intensity of IHT.However,the high LED leads to severe hot cracking within the as-built MEA,resulting in inferior ductility.By decreasing LED,the hot cracking was effectively eliminated.Meanwhile,low LED weakened the intensity of IHT and consequently inhibited kinetic conditions of dynamic recrystallization,resulting in a heterogeneous grain structure characterized by multi-scale-sized grains.This structure provides significant hetero-deformation-induced hardening during plastic deformation,enabling the alloy to have a sustainable work-hardening capacity.We expect that this work will have implications in taking full advantage of the unique IHT of the LDED process to fabricate ME As with excellent metallurgical quality and mechanical performance.

关键词： Intrinsic heat treatment Laser-directed energy deposition CrCoNi MEA Dynamic recrystallization Heterogeneous grain structure

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Higher palaeoelevation in the Baoshan Basin:Implications for landscape evolution at the southeastern margin of the Tibetan Plateau

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Journal of Palaeogeography 2024年第3期13卷 563-580页

作者： yong-jiang huang Hao-Ran Zong Shi-Tao Zhang Arata Momohara Jin-Jin Hu Lin-Bo Jia Yun-Heng Ji Zhe-Kun Zhou Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences College of Forestry Shandong Agricultural University Faculty of Land Resource Engineering Kunming University of Science and Technology Graduate School of Horticulture Chiba University Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences

Surface uplift at the southeastern margin of the Tibetan Plateau has been widely studied, but more palaeoaltimetry data are required to better understand the elevation history of this geologically complex region. In this study, fossil leaves of Abies(Pinaceae), a cool-temperate element, recovered from the latest Miocene-Pliocene Yangyi Formation of the southern Baoshan Basin, were used as a proxy to estimate the local palaeoelevation. Based on the regional modern altitude range(2100-4280 m) of the genus as well as regional temperature discrepancy(1.5°C) between the past and present, the palaeoelevation of the study area was calculated to be > 2360 m above sea level as compared to 1670 m at present. Our result suggests that the southern Baoshan Basin experienced pronounced uplift prior to the time of fossil deposition, probably as a result of crustal shortening and thickening of the northern Baoshan Terrane during the Eocene-Oligocene. We infer that surface growth in areas south of the Dali Basin may have been greater than previously interpreted,and that a widespread plateau or plateau patches higher than 2000 m probably extended southwards into at least the Baoshan Basin by the latest Miocene-Pliocene. We also infer that the elevation of the southern Baoshan Basin has decreased by at least 690 m since then, in contrast to most other scenarios in which the elevation of the southeastern margin of the Tibetan Plateau has increased or remained close to modern levels since the late Miocene. The major cause of the inferred altitude decline is likely tectonic deformation. As a transtensional graben basin, the Baoshan Basin has experienced pull-apart and base-fall movement since the late Miocene, which would reduce the altitude of its southern part located on the hanging wall. Surface erosion associated with the increased summer rainfall might also have played a role especially in reducing the local relief, although its contribution can be limited. Our study provides one of the few palaeoelevation estimates from areas so

关键词： Abies Lapse rate Palaeoaltimetry Surface uplift Tectonic movement Tibetan plateau

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Enhanced tensile properties and wear resistance of additively manufactured CoCrFeMnNi high-entropy alloy at cryogenic temperature

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Rare Metals 2022年第4期41卷 1210-1216页

作者： Hong-Ge Li Peng-Cheng Che Xiao-Kun Yang yong-jiang huang Zhi-Liang Ning Jian-Fei Sun Hong-Bo Fan School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Harbin-Electric Power Generation Equipment National Engineering Research Center Co. LtdHarbin 150028China

Here,bulk CoCrFeMnNi high-entropy alloy was prepared via laser melting deposition,and its microstructure and mechanical properties at room and cryogenic temperature were investigated by a series of microstructural character-izations and mechanical tests.The results showed that the as-built samples possessed a single fcc phase and highly dense microstructures.Compared to the mechanical prop-erties at room temperature,tensile properties,microhard-ness and wear resistance of the as-built samples showed a signiflcant enhancement at cryogenic temperature,which was attributed to the deformation mechanism converting from dislocation slipping to deformation twinning at cryogenic temperature.The formation of deformation nanotwins signiflcantly improved the deformation resis-tance in cryogenic conditions,and the sliding wear in the liquid nitrogen could decrease the oxygen concentration,suppress the generation of oxide particles and thus enhance the wear resistance.

关键词： wear cryogenic alloy

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Late Pliocene diversity and distribution of Drynaria(Polypodiaceae) in western Yunnan explained by forest vegetation and humid climates

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Plant Diversity 2016年第4期38卷 194-200页

作者： yong-jiang huang Tao Su Zhe-Kun Zhou Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of BotanyChinese Academy of Sciences Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of Sciences

The palaeodiversity of flowering plants in Yunnan has been extensively interpreted from both a molecular and fossil perspective. However, for cryptogamic plants such as ferns, the palaeodiversity remains poorly known. In this study, we describe a new ferny fossil taxon, Drynaria lanpingensis sp. nov. huang,Su et Zhou(Polypodiaceae), from the late Pliocene of northwestern Yunnan based on fragmentary frond and pinna with in situ spores. The frond is pinnatifid and the pinnae are entirely margined. The sori are arranged in one row on each side of the primary vein. The spores have a semicircular to bean-shaped equatorial view and a tuberculate surface. Taken together with previously described fossils, there are now representatives of three known fossil taxa of Drynaria from the late Pliocene of western Yunnan.These finds suggest that Drynaria diversity was considerable in the region at that time. As Drynaria is a shade-tolerant plant, growing preferably in wet conditions in the understory of forests, its extensive existence may indicate forest vegetation and humid climates in western Yunnan during the late Pliocene.This is in line with results from floristic investigations and palaeoclimatic reconstructions based on fossil floras.

关键词： Biodiversity Fern Drynaria In situ spore Late Pliocene Yunnan

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Wildfire associated with a deciduous broadleaved forest from the Neogene Baoshan Basin at the southeastern margin of the Tibetan Plateau

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古地理学报:英文版 2023年第3期12卷 448-462页

作者： yong-jiang huang Arata Momohara Shu-Feng Li Xue-ping Ji Jian Qiu Lin-Bo Jia Jin-Jin Hu Yun-Heng Ji Zhe-Kun Zhou Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of BotanyChinese Academy of SciencesKunming 650201Yunnan ProvinceChina Graduate School of Horticulture Chiba UniversityChiba 271-8510Japan Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303Yunnan ProvinceChina Kunming Natural History Museum of Zoology Kunming Institute of ZoologyChinese Academy of SciencesKunming 650223Yunnan ProvinceChina School of Material and Chemical Engineering Southwest Forestry UniversityKunming 650224Yunnan ProvinceChina

Wildfire bears a close relationship with vegetation as its fuel source.The southeastern margin of the Tibetan Plateau witnesses frequent wildfires among various types of vegetation,whereas such wide in-teractions between wildfire and vegetation remain poorly studied from geological times.In this study,we reported a local fire using sedimentary macroscopic charcoals from the latest Miocene to early Pliocene of the Baoshan Basin in this region,and then inferred the local vegetation at the time of the fire event based chiefly on the coexistent fruit and seed fossil assemblage.Our taxonomic results show that the charcoal assemblage is probably dominated by broadleaved plants and the fruit and seed fossil assemblage is apparently dominated by Salix(Salicaceae)followed by Sambucus(Adoxaceae),suggesting a deciduous broadleaved forest in which the fire likely occurred.Under a seasonally dry climate associated with the Asian monsoon,this type of vegetation might be prone to natural fire,because in the wet rainy season the plants grew well to accumulate biofuel and in the dry season abundant ground litter resulting from leaf decay would be desiccated to become highly flammable.Due to the fire-tolerant habit of Salix as the dominant plant,the forest might be in return adapted to the fire event or even more fires that potentially followed.All these may suggest a close relationship between the fire event and the reconstructed vegetation.Our finding documents a new type of wildfire—vegetation interaction,namely the interaction between wildfire and deciduous broadleaved forest,from the geological past at the southeastern margin of the Tibetan Plateau.It therefore sheds new light on the wildfire history coupling vegetation change in the region.

关键词： Charcoal Fossil carpology Salix Sambucus Precipitation seasonality

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Resistance spot welding of Ti_(40)Zr_(25)Ni_3Cu_(12)Be_(20) bulk metallic glass:experiments and finite element modeling

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Rare Metals 2017年第2期36卷 123-128页

作者： Gang Wang yong-jiang huang Deodat Makhanlall Jun Shen School of Mechanical and Automotive Engineering Anhui Polytechnic University School of Materials Science and Engineering Harbin Institute of Technology

The use of resistance spot welding（RSW）technology for joining Ti40Zr25Ni3Cu12Be20 metallic glass was investigated.The microstructure obtained from the welded BMG sample was studied.Joint without precipitates was prepared with welding current of 5.0 kA for 2cycles.A fully coupled thermal-electrical-mechanical finite element model（FEM） was developed to complement the experimental study.The simulated results agree well with the measurements.The effects of key process parameters such as welding current and welding time on the evolvement and microstructure of the weldment were determined and discussed.Moreover,the critical cooling rate for preserving the amorphous state in the weld fusion zone is determined to be approximately 1×10^3 K·s^-1.

关键词： Metallic glasses Simulations Resistance spot welding Cooling rate

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New fossil seeds of Eurya （Theaceae） from East Asia and their paleobiogeographic implications

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Plant Diversity 2016年第3期38卷 125-132页

作者： Hai Zhu yong-jiang huang Tao Su Zhe-Kun Zhou Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical Garden Chinese Academy ofSdences Mengla 666303 China University of Chinese Academy of Sdences Beijing 100049 China State Key Laboratory of Paleobiology and Stratigraphy Nanjing Institute of Geology and Paleontology Chinese Academy of Sciences Nanjing 210008 China

Eurya has an excellent fossil record in Europe,but it has only a few fossil occurrences in East Asia though this vast area houses the highest modern diversity of the genus.In this study,three-dimensionally preserved fossil seeds of Euiya stigmosa(Ludwig) Mai from the late Pliocene of northwestern Yunnan,southwestern China are described.The seeds are compressed and flattened,slightly campylotropous,and nearly circular to slightly angular in shape.The surface of the seeds is sculptured by a distinctive foveolate pattern,consisting of funnel-shaped and finely pitted cells.Each seed valve contains a reniform or horseshoe-shaped embryo cavity,a characteristic condyle structure and an internal raphe.These fossil seeds represent one of the few fossil records of Eurya in East Asia.This new finding therefore largely extends the distributional ranges of Eurya during Neogene.Fossil records summarized here show that Euiya persisted in Europe until the early Pleistocene,but disappeared thereafter.The genus might have first appeared in East Asia no later than the late Oligocene,and dispersed widely in regions such as Japan,Nepal,and southwestern China.

关键词： Seed fossil Eurya Late Pliocene Nanbanbang Northwest Yunnan China

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Nanoscratching and mechanical behaviors of high-entropy alloys with different phase constituents

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Journal of Iron and Steel Research(International) 2019年第11期26卷 1240-1248页

作者： jiang-li Ning Yun-li Feng Xu-dong Li Qi-bo Deng yong-jiang huang College of Metallurgy and Energy North China University of Science and TechnologyTangshan 063210HebeiChina Tianjin Key Laboratory of Advanced Functional Porous Materials Institute for New Energy Materials and Low-Carbon TechnologiesSchool of Materials Science and EngineeringTianjin University of TechnologyTianjin 300384China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001HeilongjiangChina

High-entropy alloys(HEAs)exhibit unique microstructural features and properties in nanoscale and atomic scale because of their multi-element alloy system.The nanoscratching behaviors of three HEAs with different phase constituents,relative to the microstructure and mechanical properties of the HEAs,were investigated.Three typical phase constituents were selected:face-centered cubic(FCC)structure,body-centered cubic(BCC)structure,and a dual-phase structure containing both FCC and BCC phases.Despite the fact that the FCC alloy has the highest ductility and strain hardening capability,it exhibited inferior scratch resistance due to the over-softening of hardness.Due to the brittle failure mode,the BCC alloy hardly exhibited desirable scratch resistance despite its highest hardness.By contrast,the nanostructured dual-phase alloy exhibited the best scratch resistance because of its good combination of strength and ductility,as well as the ductile failure mode.This research suggests that the HEA with structure comprising nanoscale hard and soft phases is desirable for nanoscratch resistance,and possesses appropriate hardness for industrial applications.

关键词： High-entropy alloy Nanoscratch Mechanical property Microstructure-Failure mode

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Three factors make bulk high-entropy alloys as effective electrocatalysts for oxygen evolution

Materials Futures

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Materials Futures 2023年第4期2卷 115-125页

作者： Tao Zhang Hui-Feng Zhao Ke-Yan Wang Zhen-Jie Chen Li Li Jing Peng Xu Peng yong-jiang huang Hai-Bin Yu Wuhan National High Magnetic Field Center&School of Physics Huazhong University of Science and TechnologyWuhan 430074People’s Republic of China College of Chemistry and Chemical Engineering Hubei UniversityWuhan 430062People’s Republic of China School of Materials Science and Engineering Center of Analysis Measurement and ComputingHarbin Institute of TechnologyHarbin 150001People’s Republic of China Faculty of Materials Science and Energy Engineering/Institute of Technology for Carbon Neutrality Shenzhen 518055People’s Republic of China Shenzhen Key Laboratory of Energy Materials for Carbon Neutrality Shenzhen Institutes of Advanced TechnologyChinese Academy of SciencesShenzhen 518055People’s Republic of China

Even in their bulk forms,complex alloys like high-entropy alloys(HEAs)exhibit favorable activity and stability as electrocatalysts for the oxygen evolution reaction(OER).However,the underlying reasons are not yet fully understood.In a family of Mo-doped CrFeCoNi-based HEAs,we have identified three crucial factors that govern their performance:(i)homogeneous solid solution phase of HEAs helps to maintain high-valence states of metals;(ii)surface reconstruction results in a hybrid material comprising amorphous domains and percolated crystalline structures;(iii)diversity of active intermediate species(M–O,M–OOH,and,notably,the abundance of superoxideμ–OO),which display stronger adsorption capacity on the reconstructed surface.These results are revealing due to their resemblance to findings in other families of electrocatalysts for OER,as well as their unique features specific to HEAs.In line with these factors,a CrFeCoNiMo0.2 bulk integrated electrode displays a low overpotential of 215 mV,rapid kinetics,and long-term stability of over 90 d.Bulk HEAs hold great potential for industrial applications.

关键词： high-entropy alloy solid solution electrocatalysis DFT calculation oxygen evolution reaction

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Fossil fruits of Firmiana and Tilia from the middle Miocene of South Korea and the efficacy of the Bering land bridge for the migration of mesothermal plants

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Plant Diversity 2021年第6期43卷 480-491页

作者： Lin-Bo Jia Gi-Soo Nam Tao Su Gregory W.Stull Shu-Feng Li yong-jiang huang Zhe-Kun Zhou CAS Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of BotanyChinese Academy of SciencesKunming 650204China Gongju National University of Education 27Ungjin-roGongju-siChungcheongnam-do 32553South Korea CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303China University of the Chinese Academy of Sciences Beijing 100049China Germplasm Bank of Wild Species Kunming Institute of BotanyChinese Academy of SciencesKunmingYunnan 650201China Department of Botany Smithsonian InstitutionWashingtonDC 20013USA

Determining whether the high-latitude Bering land bridge(BLB)was ecologically suitable for the migration of mesothermal plants is significant for Holarctic phytogeographic inferences.Paleobotanical studies provide a critical source of data on the latitudinal positions of different plant lineages at different times,permitting assessment of the efficacy of the BLB for migration.Here we report exceptionally preserved fossils of Firmiana and Tilia endochrysea from the middle Miocene of South Korea.This represents a new reliable record of Firmiana and the first discovery of the T.endochrysea lineage in the fossil record of Asia.The occurrence of these fossils in South Korea indicates that the two lineages had a distribution that extended much farther north during the middle Miocene,but they were still geographically remote from the BLB.In light of the broader fossil record of Asia,our study shows that,in the middle Miocene,some mesothermal plants apparently inhabited the territory adjacent to the BLB and thus they were possibly capable of utilizing the BLB as a migratory corridor.Some other mesothermal plants,such as Firmiana and the T.endochrysea lineages,however,are restricted to more southern regions relative to the BLB based on current fossil evidence.These lineages may have been ecologically unable to traverse the BLB,which raises questions about the efficacy of the BLB as a universal exchange route for mesothermal plants between Asia and North America during the middle Miocene.

关键词： Asia Bering land bridge Biogeography Middle Miocene Malvaceae

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