Geographical Variation in the Advertisement Calls of Leptobrachella ventripunctata(Anura:Megophryidae)in Southwestern China

In anurans,advertisement calls(ACs)are an essential form of intraspecific communication.This study evaluates geographical variation in the ACs of Leptobrachella ventripunctata in the Guizhou Plateau,southwestern China,and explores correlations between call characteristics,body size,and environmental factors.ACs are simple calls of L.ventripunctata,and apparent differences were observed in the ACs among different geographical populations of L.ventripunctata.The Call duration(CD)revealed a significant positive correlation with altitude and a significant negative correlation with temperature and humidity.Moreover,the Dominant frequency(DF)exhibited a significant negative correlation with altitude and the habitat closure degree and a significant positive correlation with temperature.These variations in ACs between different geographical populations of L.ventripunctata may critically impact the adaptive evolution of species,and the calls may also be relevant for environmental selection.

Osteology of Leptobrachella bijie(Anura,Megophryidae)

The Asian leaf litter toad genus Leptobrachella contains more than 100 species widely distributed in southwestern Asia.However,the systematic profiles of this group remain unresolved.Osteological morphology is important for taxonomic and phylogenetic studies.However,few studies have focused on the osteology of the genus.Herein,we comprehensively described the osteological features of a representative species L.bijie based on micro-CT scanning and double-staining methods.The results show that the skull of adult L.bijie is well-ossified,exhibiting sexual dimorphism and minimal intraspecific variation.The skull length is slightly greater than the width,with the maxilla slightly overlapping with the quadratojugal.The nasal connects with the sphenethmoid in males,but only part or not connects with the sphenethmoid in females.The transverse processes of the sacrum are robust and symmetrically butterfly-shaped,and the presacral vertebrae are procoelous.The pectoral girdle is arciferous.The phalangeal formula is 2-2-3-3 for the hand,and 2-2-3-4-3 for the foot.This study provides the first detailed and comprehensive osteological accounts of the genus Leptobrachella.

Foraging habitat selection of overwintering Black-necked Cranes in the farming area surrounding the Caohai Wetland, Guizhou Province, China

Background: Understanding how overwintering birds choose foraging habitats is very important for conservation management. The overwintering Black-necked Crane(Grus nigricollis) feeds on crop remains in farmlands;thus, reasonable conservation management of this type of farmland that surrounds wetlands is critical for the overwintering populations of the Black-necked Crane;however, it is not clear how the Black-necked Crane chooses the foraging land in the farmland.Methods: A thorough field positioning survey of all foraging sites in farmland areas around the Caohai Wetland and a-sampling analysis of habitat selection by the Black-necked Crane were conducted during the winters from 20162017 and 2017-2018.Results: Multiple factors contributed to the selection of foraging habitat in farmlands, i.e., food factors(crop remains and tillage methods) > human disturbance factors(distance to road and settlement) > topography factors(slope aspect), listed according to the strength of influence. Additionally, Black-necked Cranes tend to choose farmland sites where there was no machine tillage, the crop remains were > 500 g/m^2, the distance to residences ranged from 100 to 500 m, the distance to roads ranged from 50 to 100 m, and the slopes exhibited western or eastern aspects. As the winters progressed, the volume of the edible crop remains declined, and the influences of the other main factors also changed, i.e., the factors of human disturbance(distance to road and settlement) became less important, while the effect of the food factor(crop remains) was strengthened. Thus, the foraging sites near the road became more important.Conclusion: The farming area surrounding the Caohai Wetland is very important for the overwintering Black-necked Crane. Food factors and human disturbance factors are the main factors that influence the choice of feeding ground.

Formation and Evolution of Surface Morphology in Overhang Structure of IN718 Superalloy Fabricated by Laser Powder Bed Fusion

Controlling the overhang surface quality is still a formidable challenge in manufacturing the components with complex structures during laser powder bed fusion(LPBF).This study systematically uncovers the effects of the volume energy density(VED)and overhang angle on the evolution of surface morphology and corresponding surface roughness(Ra)of top and down-skin surfaces of IN718 superalloy samples.The results show that balling,Plateau-Rayleigh instability,open pore and humping caused by the material stacking are the main factors contributing to the apparent deterioration of top surface quality.When the VED is 80–100 J/mm^(3),the high down-skin surface roughness is attributed to the serious dross caused by recoil pressure and sinking of the melt pool.Using insufficient VED(15–50 J/mm^(3))can easily lead to poor metallurgical bonding and material spalling on the down-skin surface.In addition,overhang angle also significantly affects down-skin surface roughness due to the stair effect and the adhered unmelted powders.An improvement in the surface quality of down-skin surface is observed when the overhang angle increases.Based on the finding of this investigation,an optical VED(59.5 J/mm^(3))significantly improves the top and down-skin surface quality and porosity of overhang samples.This study provides an insight into synergy ascension of the top and down-skin surface quality in the overhang structure.

Effects of Post-Heat Treatment and Carbide Precipitates on Strength-Ductility Balance of GH3536 Superalloy Prepared by Selective Laser Melting

The strength and ductility cannot achieve a good tradeoff for some superalloy(e.g.GH3536)prepared by selective laser melting(SLM),which seriously restricts their industrial applications.This work examined the effect of post-heat treatment(HT)on the microstructure and mechanical properties of GH3536 produced by SLM.In particular,the influence of carbide precipitate morphology and distribution on strength and ductility of the alloy after heat treatment was discussed.After aging at 650°C(denoted as HT1),the Cr23C6 carbides were distributed in chains.The ductility increased by approximately 31%,while the strength slightly decreased.After aging at 745°C(denoted as HT2),the Cr23C6 carbides were distributed in chains.However,the HT2 samples showed an increase in ductility of~58%and no reduction in strength.As the dislocation density of HT2 sample was higher than that of the HT1 sample,the chain carbides could be pinned to the grain boundaries,consequently improving the ductility but no loss in strength as compared with the as-deposited samples.When the aging temperature was increased to 900°C(denoted as HT3),the carbides were distributed in a discontinuous granular form.As a result,the HT3 samples presented the lowest dislocation density which reduced the strength.

Coupling phase field with creep damage to study γ’evolution and creep deformation of single crystal superalloys

A phase-field model coupling with elastoplastic de fo rmation and creep damage has been built to study the micro structural evolution and deformation behavior for Ni-Al single crystal alloy during the whole creep processing.The relevant experiments were conducted to verify the model validity.The simulation re sults show that under the tensile creep at 1223 K/100 MPa,cubic γ’phases coarsen along the direction parallel to the axis of tensile stress during the first two creep stages;and spindle-shaped and wavy γ’phases are fo rmed during tertiary creep,similar to the experimental results.The evolution mechanism of γ’phases is analyzed from the perspective of changes of stress and strain fields.The"is land-like"γ phase is observed and its formation mechanism is discussed.With the increase of creep stress,the directional coarsening of γ’phase is accelerated,the steady-state creep rate is increased and the creep life is decreased.The comparison between simulated and experimental creep curves shows that this phase-field model can effectively simulate the performance changes during the first two creep stages and predict the influence of creep stresses on creep properties.Our work provides a potential approach to synchronously simulate the creep microstructure and property of superalloys strengthened by γ’precipitates.

Correlation Between Phase Stability and Tensile Properties of the Ni-Based Superalloy MAR-M247

Phase stability and its effect on tensile properties of MAR-M247 alloy have been investigated during thermal exposure at 800–900°C for up to 10,000 h.Detailed investigations reveal that the larger secondaryγ′phase has no obvious growth,but the smaller tertiaryγ′phase obviously coarsens and the coalescence occurs during thermal exposure at 850°C and below.γ′coarsening behavior is consistent with the description of Ostwald ripening theory beforeγ′coalescence.Hf-rich blocky MC carbide shows excellent thermal stability,but Ta-rich script-type MC carbide gradually degenerates via reaction,MC+γ→M_(23)C_(6)+γ′and finally formsγ film around MC and M_(23)C_(6) carbides.With increasing thermal exposure time,the tensile strength decreases.The ductility first increases and then decreases during exposure at 800°C,but it decreases continuously at 900°C.In addition,the ductility keeps almost constant when the exposure time is longer than 5000 h.

Tailoring Microstructure and Microsegregation in a Directionally Solidified Ni-Based SX Superalloy by a Weak Transverse Static Magnetic Field

A weak transverse static magnetic field(WTSMF,0–0.5 T)is applied to the directional solidification process of a DD3 Ni-based SX superalloy,aiming to tailor the microstructure and microsegregation of alloys.The mechanisms of microstructural refinement and microsegregation distribution caused by a WTSMF during directional solidification are discussed.It is shown that the primary dendrite arm spacing is rapidly reduced from 181 to 143μm,and the average size ofγ′phase is significantly refined from 0.85 to 0.25μm as the magnetic field increases from 0 to 0.5 T.At the same time,the volumefractions ofγ/γ′eutectic and the segregation coefficient are also gradually decreased.The 3D numerical simulations of the multiscale convection in liquid phase show that the modifications of the microstructure and microsegregation in DD3 are mainly attributed to the enhanced liquid flow caused by thermoelectric magnetic convection(TEMC)at dendrite/sample scale under the WTSMF.The maximum of the TEMC increases with increasing the magnetic field intensity.This work paves a simple way to optimize the microstructure and microsegregation in directionally solidified Ni-based SX superalloys without changing the processing parameters and composition.

Cracking behavior of newly-developed high strength eutectic high entropy alloy matrix composites manufactured by laser powder bed fusion

A novel AlCoCrFeNi2.1 eutectic high entropy alloy(EHEA)composite doped with SiC particles was designed and fabricated by laser powder bed fusion(LPBF).Its microstructure characteristic,tensile properties,and metallurgical defects,with an emphasis on cracking behavior,have been investigated.The results showed that the addition of SiC particles into the AlCoCrFeNi_(2.1)matrix enabled the development of a{100}texture and highly elongated columnar grains,which were the main contributors to mechanical behavior anisotropy.The ultimate tensile strength of 1466±26 MPa and elongation of 9%±3%achieved in the as-deposited EHEA composite surpassed those of advanced metal alloys subjected to additive manufacturing processes.Unfortunately,severe horizontal and longitudinal cracks,as well as a few micro-cracks were observed in the as-deposited bulk samples.Micro-cracks were verified to be associated with the aggregation of carbon and oxide particles.They formed in the final stage of solidification owing to insufficient liquid feeding ability and solidification contraction.The formation of macroscopic cracking was induced by the tensile stress accumulations at sample edges,and the stress concentration areas where microcracks and pores were located were the predominant propagation location.This work provides guidelines for defect control in SiC-reinforced EHEA,assisting in the high-performance design and integrated manufacturing of EHEA composite components.

Effect of seed orientations on crystallographic texture control in faceted Al2O3/YAG eutectic ceramic during directional solidification

Crystallographic texture control is a major challenge in directionally solidified multiphase eutectic ceramics with complex faceted growth characteristics.In this study,the Czochralski(CZ)technique is proposed to prepare eutectic single crystal ceramic with large size(30 mm×125 mm).A highly oriented and unique texture of Al_(2)O_(3)/Y_(3)Al_(5)O_(12)(YAG)eutectic ceramic is formed via the 112¯0Al_(2)O_(3) single crystal seed induction based on crystallographic orientation tailoring.The orientations of Al_(2)O_(3)/YAG eutectic are more strictly constrained by single crystal seed induction on the basis of the minimum interface energy principle,resulting in a defined single orientation relationship along the solidification direction.In particular,the single crystallographic orientation can be obtained in a short competitive solidification distance under the influence of epitaxial solidification from single crystal seed.Therefore,it has been confirmed that the orientations of 112¯0Al_(2)O_(3) and 111YAG are preferentially stabilized with the minimum under-cooling during directional solidification.Crystallographic orientation disturbances and instabilities due to polycrystalline crystal seed are avoided.Finally,the successful texture control inducted by 112¯0Al_(2)O_(3) single crystal seed can provide a promising orientation design pathway for faced oxide eutectic solidification.

Unveiling the dynamic instability mechanism of microstructure transformation in faceted oxide eutectic composite ceramics

Microstructure control is a great challenge in the high-temperature gradient directional solidification of eutectic composite ceramics due to the complex solidification behavior.Herein,the microstructure trans-formation of faceted Al_(2)O_(3)/Er_(3)Al_(5)O_(12) thermal emission eutectic composite ceramics is explored over wide ranges of compositions(13.5 mol%-22.5 mol%Er_(2)O_(3))and solidification rates(2-200μm/s).Entirely cou-pled eutectics with primary phases suppressed are fabricated and the coupled zone is broadened in a wide range of 15.5 mol%-22.5 mol%Er_(2)O_(3) at low solidification rates.The competitive growth between eutectic and dendrite is evaluated on the basis of the maximum interface temperature criterion.In ad-dition,the mechanisms of irregular eutectic spacing selection and adjustment under different solidifi-cation rates are revealed based on Magnin-Kurz model.A successful prediction of lamellar to rod-like eutectics is achieved associated with the dynamic instability of lamellar eutectic and the corresponding enlarged coexistence region is mapped based on the interface undercooling.According to the well mi-crostructure tailoring,the flexural strength of Al_(2)O_(3)/Er_(3)Al_(5)O_(12) eutectic composite ceramics has improved from 508 MPa up to 1800 MPa due to the refined eutectic spacing with low fluctuation.The eutectic composite ceramics show strong selective optical absorption and the intensity increases with the refin-ing microstructure.The as-designed Al_(2)O_(3)/Er_(3)Al_(5)O_(12) composites with microstructural tailoring have great potential as integrations of structural and functional materials.

High temperature calcium-magnesium-alumina-silicate(CMAS)corrosion behavior of directionally solidified Al_(2)O_(3)/YAG eutectic ceramic

1.Introduction Modern turbine engines can be substantially damaged when the airborne silicate-based particles(fly ash,desert sand,volcanic ash,runway debris,etc.)are ingested into jet engines at high temperatures(1150−1250℃)[1-4],leading to severe CaO-MgO-Al_(2)O_(3)-SiO_(2)(CMAS)corrosion during their service life.In order to extend the engine life,many efforts have been devoted to thermal barrier coatings(TBCs)and environmental barrier coatings(EBCs)to protect the substrate from corrosion by molten CMAS[5-7].To be specific,thermochemical and thermomechanical corrosion are the two main mechanisms of CMAS corrosion[8].The structure and composition of the coatings were changed due to the chemical reaction between the molten CMAS and coating,the detrimental phases were then precipitated[9,10].

贵州梵净山国家级自然保护区鸟兽红外相机监测

红外相机监测是了解野生动物多样性现状、动态变化和面临威胁的重要手段。本研究采用网格抽样调查法,在贵州梵净山国家级自然保护区内选取2个监测样区共40个监测位点布设红外相机,对区内兽类和鸟类物种进行监测调查。2017年4月至2018年12月间,红外相机累积监测14,808个相机工作日,共收集有效照片14,119张,独立有效物种照片3,199张。共鉴定野生动物9目22科61种,其中兽类26种,隶属于4目12科;鸟类35种,隶属于5目10科。记录到国家I级重点保护野生动物2种:黔金丝猴(Rhinopithecusbrelichi)和白颈长尾雉(Syrmaticusellioti),国家II级重点保护野生动物9种;被IUCN红色名录评估为濒危(EN)的1种、易危(VU)的5种、近危(NT)的8种。物种的相对多度指数(relative abundance index, RAI)分析结果显示,藏酋猴(Macaca thibetana, RAI=28.23)、毛冠鹿(Elaphodus cephalophus, RAI=15.46)、野猪(Sus scrofa, RAI=11.82)、小麂(Muntiacus reevesi, RAI=9.05)、黔金丝猴(RAI=7.70)为相对多度最高的5种兽类;紫啸鸫(Myophonus insularis, RAI=10.33)、红腹角雉(Tragopan temminckii, RAI=9.59)、红腹锦鸡(Chrysolophus pictus, RAI=6.96)、白颈长尾雉(RAI=3.71)、勺鸡(Pucrasia macrolopha, RAI=1.55)为相对多度最高的5种鸟类。另外,红外相机还监测到较多的家畜活动(RAI=11.14)和人为活动(RAI=12.90),保护区管理部门仍需采取相应管理措施,进一步提高周边居民的保护意识,促进保护区与社区的协调发展。

贵州赤水桫椤国家级自然保护区鸟兽多样性红外相机初步监测

红外相机监测是了解野生动物多样性和威胁因素的重要手段。本研究采用网格法和分层抽样调查法,在贵州赤水桫椤国家级自然保护区内选取20个监测位点布设红外相机,对区内鸟兽物种多样性进行监测。2015年8月至2017年8月,红外相机累计工作6,370个工作日,共拍摄45,953张照片,独立有效照片1,936张。准确鉴定出兽类4目8科19种,鸟类4目11科28种,其中,国家II级重点保护野生动物7种。相对丰富度指数(RAI)排前五位的兽类依次是毛冠鹿(Elaphodus cephalophus)、鼬獾(Melogale moschata)、藏酋猴(Macaca thibetana)、小麂(Muntiacus reevesi)和野猪(Sus scrofa);鸟类依次是紫啸鸫(Myophonus caeruleus)、红腹角雉(Tragopan temminckii)、灰胸竹鸡(Bambusicola thoracicus)、黑喉噪鹛(Garrulax chinensis)和棕颈钩嘴鹛(Pomatorhinus ruficollis)。物种积累曲线结果表明,兽类稀疏化曲线在300天后趋于稳定,表明监测取样已较充分,而鸟类监测物种数随时间积累依旧保持增长趋势。

西南喀斯特地区生物文化多样性的演化与耦合:以贵州兴义坡岗自然保护区为例

本文以具有典型喀斯特环境特点的贵州兴义坡岗自然保护区为例开展实地调查和文献研究。通过层次分析法和人与自然耦合系统模型构建,从文化景观视角探讨了喀斯特地区自然与文化系统的历史演化过程中,国家生态政策制度与乡规民约等乡土保护体系对生物文化多样性的驱动作用。研究结果表明:坡岗保护区经历了管护主体和保护利用态度的转变,保存了典型的喀斯特自然生态系统,当地世居的少数民族群体在长期生存与适应过程中创造了极具特色的传统民族文化。坡岗自然保护区丰富的生物多样性与文化多样性形成一个地理重合、协同进化且相互作用的维持系统。生物文化多样性耦合体系主要存在国家政策制度类与乡规民约等乡土文化类两种驱动因素。应加强西南喀斯特地区的生物文化多样性的保护,推动该地区生物多样性与文化多样性的协同发展;除了政策与制度类驱动因子的直接作用,还需要注重村规民约以及生态传统知识等乡土文化的驱动作用,以避免保护区自然与文化保护体系的割离。

Preparation of large-size Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)ternary eutectic ceramic rod by laser directed energy deposition and its microstructure homogenization mechanism

Laser 3D printing based on melt growth has great potential in rapid preparation of Al_(2)O_(3)-based eutectic ce ramics.In this work,la rge-scale Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)ternary eutectic ceramic rod with diameter of 4-5 mm and height higher than 250 mm was additively manufactured by laser directed energy deposition.Especially,heat treatment was applied to eliminate the microstructure heterogeneity in the as-deposited eutectic ceramic,and the microstructure homogenization mechanism was studied in depth.The results indicate that colonies and banded structures completely disappear after the heat treatment,producing a homogeneous network eutectic structure.The microstructure homogenization is revealed to experience three stages of discontinuous coarsening,continuous coarsening and microstructure coalescence.Additionally,it is found that the eutectic spacing linearly increases with the heat treatment time,meaning that the coarsening behavior of the laser 3D-printed Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)eutectic ceramic satisfies well with the Graham-Kraft model.

Unique strength-ductility balance of AlCoCrFeNi_(2.1)eutectic high entropy alloy with ultra-fine duplex microstructure prepared by selective laser melting

As a typical dual-phase eutectic high entropy alloy(EHEA),AlCoCrFeNi_(2.1)can achieve the fair matching of strength and ductility,which has attracted wide attention.However,the engineering applications of as-cast AlCoCrFeNi_(2.1)EHEAs still face challenges,such as coarse grain and low yield strength resulting from low solidification rate and temperature gradient.In this study,selective laser melting(SLM)was introduced into the preparation of AlCoCrFeNi_(2.1)EHEA to realize unique strength-ductility balance,with emphasis on investigating the effects of processing parameters on its eutectic microstructure and properties.The results show that the SLM-ed samples exhibit a completely eutectic structure consisting of ultra-fine face-centered cubic(FCC)and ordered body-centered cubic(B2)phases,and the duplex microstructure undergoes a morphological evolution from lamellar structure to cellular structure as laser energy input reducing.The SLM-ed AlCoCrFeNi_(2.1)EHEA presents an excellent match of high tensile strength(1271 MPa),yield strength(966 MPa),and good ductility(22.5%)at room temperature,which are significantly enhanced by the ultra-fine grains and heterogeneous structure due to rapid solidification rate and high temperature gradient during SLM.Especially,the yield strength increment of~50%is realized with no loss in ductility as compared with the as-cast samples with the same composition.On this basis,the precise complex component with excellent mechanical properties is well achieved.This work paves the way for the performance improvement and complex parts preparation of EHEA by microstructural design using laser additive manufacturing.

Distribution control and formation mechanism of gas inclusions in directionally solidified Al2O3-Er3Al5O12-ZrO2 ternary eutectic ceramic by laser floating zone melting

Distribution control and formation mechanism of gas inclusions formed in directionally solidified Al2O3-Er3Al5O12-ZrO2 eutectic ceramic rods are explored during laser floating zone melting. In atmospheric environment, highly-dense bubble-free eutectic rods are well fabricated at low solidification rate(<25μm/s). Gas inclusions form intermittently when the solidification rate is in the range of 25-50 μm/s,but produce continuously at higher solidification rates(100-200 μm/s). The gas inclusions exhibit an elongated finger-like pattern along the growth direction, which of the maximum value of diameter first increases and then decreases with increasing the solidification rate. Meanwhile, the volume fraction of gas inclusions increased gradually with the solidification rate. Based on the effect of surface tension gradient, heterogeneous nucleation of gas bubbles is evaluated to be the primary formation mechanism of gas inclusions.

Phase growth patterns for Al_(2)O_(3)/GdAlO_(3)eutectics over wide ranges of compositions and solidification rates

Phase selection and growth characteristics of directionally solidified Al_(2)O_(3)/GdAlO_3(GAP)faceted eutectic ce ramics are investigated over wide ranges of compositions and solidification rates to explore the eutectic coupled zone.Through the obse rvation of the quenched solid-liquid interface,the competitive growth of primary faceted Al_(2)O_(3)phase,prima ry non-faceted GAP phase and Al_(2)O_(3)/GAP eutectic with diffe rent morphologies is detected.Microstructure transitions from wholly eutectic to primary Al_(2)O_(3)(GAP)dendrite plus eutectic and then to wholly eutectic are found in Al_(2)O_(3)-2 O mol%Gd_(2)O_(3)hypoeutectic(Al_(2)O_(3)-26 mol%Gd_(2)O_(3)hypereutectic)ceramics with the increase of solidification rate.The dendrite growth of faceted Al_(2)O_(3)and non-faceted GAP phases are well predicted by KGT model,which have introduced appro p riate dimensionless supersaturationΩto characterize the anisotropic growth of dendrites.Based on the maximum interface temperature criterion,the competitive growth of primary phase and eutectic is analyzed theoretically and the predicted coupled zone of Al_(2)O_(3)/GAP eutectic ceramics is in good agreement with the experimental results.Besides,the influence of microstructure with these different morphologies on the flexural strength of Al_(2)O_(3)/GAP eutectic ceramics is studied.

A Review of Emerging Metallic System for High-Energy Beam Additive Manufacturing: Al–Co–Cr–Fe–Ni High Entropy Alloys

Al–Co–Cr–Fe–Ni high entropy alloy(HEA) system is a newly developed category of metallic materials possessing unique microstructure, mechanical and functional properties, which presents many promising industrial applications. In recent years, additive manufacturing technology has given rise to a great potential for fabricating HEA parts of ultra-fine grains and geometrical complexity, thereby attracting great interest of researchers. Herein, a comprehensive review emphasizes on the recent developments in high-energy beam additive manufacturing of Al–Co–Cr–Fe–Ni HEA, in the aspects of their printing processes, microstructures, properties, defects, and post treatments. The technical characteristics of three typical high-energy beam additive manufacturing technologies for printing HEA, namely, selective laser melting(SLM), selective electron beam melting(SEBM), and directed energy deposition(DED) are systematically summarized. Typical crystal structure, grain, microstructure, as well as corresponding properties of Al–Co–Cr–Fe–Ni HEA manufactured by those technologies are primarily presented and discussed. It also elaborates the formation mechanisms of harmful defects related to the rapid solidification and complex thermal cycle during high-energy beam additive manufacturing. Furthermore, several kinds of post treatments with an aim to improve performance of HEA are illustrated. Finally, future research directions for HEA by additive manufacturing are outlined to tackle current challenges and accelerate their applications in industrial fields.