A large language model-powered literature review for high-angle annular dark field imaging

High-angle annular dark field(HAADF)imaging in scanning transmission electron microscopy(STEM)has become an indispensable tool in materials science due to its ability to offer sub-°A resolution and provide chemical information through Z-contrast.This study leverages large language models(LLMs)to conduct a comprehensive bibliometric analysis of a large amount of HAADF-related literature(more than 41000 papers).By using LLMs,specifically ChatGPT,we were able to extract detailed information on applications,sample preparation methods,instruments used,and study conclusions.The findings highlight the capability of LLMs to provide a new perspective into HAADF imaging,underscoring its increasingly important role in materials science.Moreover,the rich information extracted from these publications can be harnessed to develop AI models that enhance the automation and intelligence of electron microscopes.

Lithium mapping in a Mg-9Li-4Al-1Zn alloy using electron energy-loss spectroscopy

Magnesium-lithium alloys with high lithium content have been attracting significant attention because of their low density,high formability and corrosion resistance.These properties are dependent on the distribution of lithium,which is difficult to map in the presence of magnesium.In this work,a ratio spectrum-imaging method with electron energy-loss spectroscopy(EELS)is demonstrated,which enables the mapping of lithium.In application to LAZ941(Mg-9Li-4Al-1Zn in wt.%),this technique revealed that a key precipitate in the microstructure,previously thought by some to be Mg_(17)Al_(12),is in fact rich in lithium.This result was corroborated with a structural investigation by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),showing this phase to be Al_(1-x)Zn_(x)Li,with x<<1.This work indicates the potential offered by this technique for mapping lithium in materials.

The Maximum Effective Moment Criterion (MEMC) and Its Implications in Structural Geology

The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which is mathematically expressed as Meff = （（σ1-σ3） L.sin 2α sin α）/2, where σ1-σ3 represents the yield strength of the related rock, L is a unit length and a is the angle between σ1 and deformation bands. This criterion demonstrates that the maximum value appears at angles of ±54.7° to σ1 and there is a slight difference in the moment in the range of 55°±10°. The range covers the whole observations available from nature and experiments. Its major implications include： （1） it can be used to determine the stress state when the related deformation features formed; （2） it provides a new approach to determine the Wk of the related ductile shear zone if only the ratio of the vorticity and strain rate remains fixed; （3） It can be used to explain （a） the obtuse angle in the contraction direction of conjugate kink-bands and extensional crenulation cleavages, （b） formation of low-angle normal faults and high-angle reverse faults, （c） lozenge ductile shear zones in basement terranes, （d） some crocodile structures in seismic profiles and （e） detachment folds in foreland basins.

Microstructure and mechanical properties of TC4 titanium alloy K-TIG welded joints

The 12 mm-thick Ti−6Al−4V(TC4)titanium alloy plates were welded using keyhole tungsten inert gas(K-TIG)welding at various heat inputs.The microstructure,grain boundary(GB)characteristics and mechanical properties of the weld metal zone(WMZ)were analyzed.The test results show that the K-TIG welds are well formed,and no obvious defects are observed when the heat input is 2.30−2.62 kJ/mm.When the heat input gradually increases,αlaths increase in length,andα′phase and residualβphase are reduced.The electron backscatter diffraction(EBSD)test results indicate that the high-angle GB proportion in the WMZ increases with the increase of heat input.The tensile strength of the WMZ gradually decreases and the elongation of the WMZ increases when the heat input increases from 2.30 to 2.62 kJ/mm.The impact toughness of the WMZ increases as the heat input increases.

Effects of chromium on the microstructure and hot ductility of Nb-microalloyed steel

It is well-known that the surface quality of the niobium microalloy profiled billet directly affects the comprehensive mechanical properties of the H-beam.The effects of chromium on theγ/αphase transformation and high-temperature mechanical properties of Nb-microalloyed steel were studied by Gleeble tensile and high-temperature in-situ observation experiments.Results indicated that the starting temperature of the γ→αphase transformation decreases with increasing Cr content.The hot ductility of Nb-microalloyed steel is improved by adding 0.12wt% Cr.Chromium atoms inhibit the diffusion of carbon atoms,which reduces the thickness of grain boundary ferrite.The number fractions of high-angle grain boundaries increase with increasing chromium content.In particular,the proportion is up to 48.7% when the Cr content is 0.12wt%.The high-angle grain boundaries hinder the crack propagation and improve the ductility of Nb-microalloyed steel.

Strengthening mechanisms of reduced activation ferritic/martensitic steels:A review

This review summarizes the strengthening mechanisms of reduced activation ferritic/martensitic(RAFM)steels.High-angle grain boundaries,subgrain boundaries,nano-sized M_(23)C_(6),and MX carbide precipitates effectively hinder dislocation motion and increase high-temperature strength.M23C6 carbides are easily coarsened under high temperatures,thereby weakening their ability to block dislocations.Creep properties are improved through the reduction of M23C6 carbides.Thus,the loss of strength must be compensated by other strengthening mechanisms.This review also outlines the recent progress in the development of RAFM steels.Oxide dispersion-strengthened steels prevent M23C6 precipitation by reducing C content to increase creep life and introduce a high density of nano-sized oxide precipitates to offset the reduced strength.Severe plastic deformation methods can substantially refine subgrains and MX carbides in the steel.The thermal deformation strengthening of RAFM steels mainly relies on thermo-mechanical treatment to increase the MX carbide and subgrain boundaries.This procedure increases the creep life of TMT(thermo-mechanical treatment)9Cr-1W-0.06Ta steel by~20 times compared with those of F82H and Eurofer 97 steels under 550℃/260 MPa.

Fast anisotropic resistivities inversion of loggingwhile-drilling resistivity measurements in highangle and horizontal wells

Information about anisotropic resistivity is essential in real-time correlation,updating of formation model and making more confi dent geosteering decisions in logging-while-drilling(LWD)application.However,abnormal responses such as curve separations and apparent resistivity“horns”often exist in the LWD resistivity measurements due to the infl uences of complex downhole environments.Thus,accurate formation resistivity is not readily available.In this paper,we present an effi cient inversion scheme for the rapid estimation of anisotropic resistivity from LWD resistivity measurements acquired in high-angle and horizontal wells.Several strategies are adopted in the inversion:(1)a one-dimensional(1D)simulator with a simplifi ed three-layered model guarantees the forward speed and keeps the number of inverted parameters as few as possible;(2)combined with geological and petrophysical bounds,the tool constraints derived from a detection capability analysis of LWD resistivity measurements are applied to scale down the inverted parameters’searching scope,which avoids meaningless solutions and accelerates the inversion signifi cantly;(3)multiple-initial guesses are used in the inversion to ensure a global solution.Inversion results over synthetic examples demonstrate that the proposed 1D inversion algorithm is well suited for complex formation structures.It is also robust and fast in extracting anisotropic resistivities from LWD resistivity measurements.

Dilute long period stacking/order(LPSO)-variant phases along the composition gradient in a Mg-Ho-Cu alloy

We have systematically investigated the microstructures of as-cast Mg_(97.49)Ho_(1.99)Cu_(0.43)Zr_(0.09)alloy by atomic resolution high-angle annular dark field scanning transmission electron microscopy(HAADF-STEM), revealing the coexistence of 18R, 14H and 24R long period stacking/order(LPSO) phases with fully coherent interfaces along step-like composition gradient in a blocky intermetallic compound distributed at grain boundary. The short-range order(SRO) L1_(2)-type Cu_(6)Ho_(8)clusters embedded across AB’C’A-stacking fault layers are directly revealed at atomic scale. Importantly, the order degree of SRO clusters in the present dilute alloy is significant lower than previous 6M and 7M in-plane order reported in ternary Mg-TM(transition metal)-RE(rare earth) alloys, which can be well matched by 9M in-plane order. This directly demonstrates that SRO in-plane L1_(2)-type clusters can be expanded into more dilute composition regions bounded along the definite TM/RE ratio of 3/4. In addition, the estimated chemical compositions of solute enriched stacking fault(SESF) in all LPSO variants are almost identical with the ideal SESF composition of 9M in-plane order, regardless of the type of LPSO phases. The results further support the viewpoint that robust L1_(2)-type TM_(6)RE_(8)clusters play an important role in governing LPSO phase formation.

Effect of predeformation on globularization of Ti-5Al-2Sn-2Zr-4Mo-4Cr during annealing

The microstructure evolution during annealing of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy was investigated. The results show that for the alloy compressed at 810 °C and 1.0 s^-1, deformation amount（height reduction） 20% and 50% and annealed at 810 °C, thermal grooving by penetration of β phase is sufficient during the first 20 min annealing, resulting in a sharp increase in globularization fraction. The globularization fraction continuously increases with the increase of annealing time, and a height reduction of 50% leads to a near globular microstructure after annealing for 4 h. For the alloy with deformation amount of 50% by compressing at 810 °C, 0.01 s^-1, and then annealed at 810 °C, thermal grooving is limited during the first 20 min of annealing and large quantities of high-angle grain boundaries（HABs） remain. With long time annealing, the chain-like α grains are developed due to the HABs, termination migration and Ostwald ripening. The present results suggest that a higher strain rate and a larger height reduction are necessary before annealing to achieve a globular microstructure of Ti-5Al-2Sn-2Zr-4Mo-4Cr.

Seeing Is Believing:Directly Imaging Contractions of Artificial Molecular Muscles with Platinum Atom Markers

Artificial molecular muscles undergo well-controlled contractile and extensile motions upon external stimulation,leading to remarkable length changes.Evaluating such length changes at the molecular level is essential to the design of integrated artificial molecular muscles that mimic biological muscles.Taking advantage of the strong contrast of platinum(Pt)atoms in high-angle annular dark-field scanning transmission electron microscopy images,we imaged Pt-containing molecular[c2]daisy chains directly by employing metal atom markers.The length changes and associated conformational transformations of these newly developed artificial molecular muscles have been measured experimentally in combination with theoretical calculations.The contraction ratios of these two molecular muscles with the TEMPO or pyrene anchoring group were calculated to be 21.0%or 15.7%respectively,suggesting a substantial anchoring effect.This study demonstrates the experimental measurement of the length changes of artificial molecular muscles and provides a new avenue for investigating the motion of artificial molecular machines.

In situ trapped high-density single metal atoms within graphene： Iron-containing hybrids as representatives for efficient oxygen reduction

Atomically dispersed catalysts have attracted attention in energy conversion applications because their efficiency and chemoselectivity for special catalysis are superior to those of traditional catalysts. However, they have limitations owing to the extremely low metal-loading content on supports, difficulty in the precise control of the metal location and amount as well as low stability at high temperatures. We prepared a highly doped single metal atom hybrid via a single-step thermal pyrolysis of glucose, dicyandiamide, and inorganic metal salts. High-angle annular dark field-scanning transmission electron microscopy （HAADF-STEM） and X-ray absorption fine structure spectroscopy （XAFS） revealed that nitrogen atoms doped into the graphene matrix were pivotal for metal atom stabilization by generating a metal-Nx coordination structure. Due to the strong anchoring effect of the graphene matrix, the metal loading content was over 4 wt.% in the isolated atomic hybrid （the Pt content was as high as 9.26 wt.% in the Pt-doped hybrid）. Furthermore, the single iron-doped hybrid （Fe@N-doped graphene） showed a remarkable electrocatalytic performance for the oxygen reduction reaction. The peak power density was - 199 mW·cm-2 at a current density of 310 mA·cm-2 and superior to that of a commercial Pt/C catalyst when it was used as a cathode catalyst in assembled zinc-air batteries. This work offered a feasible approach to design and fabricate highly doped single metal atoms （SMAs） catalysts for potential energy applications.

Atomic-scale mechanism of the θ’’→θ’ phase transformation in Al-Cu alloys

The phase transformation of θ’’→θ’ in an Al-5.7 Cu alloy was investigated by aberration-corrected scanning transmission electron microscopy, and the tranformation mode of θ’’→θ’ during aging treatment was clarified. In the presence of the θ’ phases, θ’ was found to be formed by in-situ transformation fromθ’’ with the same plate shape, size and broad faces. The transformation starts from multiple sites within the θ’ precipitate and the whole θ’ phase finally forms as the preferential θ’ sections grow and connect with each other. Antiphase domain boundaries are also found in some θ’ precipitates when the disregistry exists between different θ’ sections.

Effect of Rare Earth and Cooling Process on Microstructure and Mechanical Properties of an Ultra-Cleaned X80 Pipeline Steel

In order to explore the eff ect of a small amount of rare earth addition in ultra-cleaned pipeline steel and the influence of the cooling process on the tensile and impact properties,three API X80 pipeline steels were fabricated by varying RE addition and the cooling process at the same time.Three microstructures with different features for a low C high Nb microalloyed high-strength pipeline steel and the corresponding mechanical properties were investigated.The results showed that even in the ultra-cleaned steel with O and S contents less than 10 ppm,the addition of RE would still cause an increase in the volume fraction of inclusions consisting of complicated RE oxysulfide and RE sulfide.More inclusions formed in the 112 ppm RE steel were harmful to the low temperature toughness,while few inclusions formed in the 47 ppm RE steel had almost no influence on the low temperature toughness.The two RE additions had no effect on strength of the steels.As the finishing cooling temperature was increased and the cooling rate was decreased within a certain range,the volume fractions of polygonal ferrite and quasi-polygonal ferrite as well as the number density and size of martensite–austenite islands were increased.Under such combined effect,the strength of the steels had almost no change.As the finishing cooling temperature was increased from 481 to 584℃and the cooling rate was reduced from 20 to 13℃/s,for the steel with 112 ppm addition of RE,there was an obvious decrease in the low temperature toughness.The reduced value(about 33 J)of the USE of steel consisted of two parts including the influence(about 18 J)of more inclusions formed due to 112 ppm addition of RE and the eff ect(about 15 J)of the lower high-angle grain boundaries.

Interactions between cadmium and multiple precipitates in an Al-Li-Cu alloy:Improving aging kinetics and precipitation hardening

This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd(0.06 at.%).The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations.A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner.Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets.It is highly likely that these nanoparticles act as heterogeneous nucleation sites,which consequently leads to a higher number density of T1 precipitates.Moreover,Cd atoms were preferentially segregated withinδprecipitates,which can be attributed to the strong bonding between Li and Cd.The interactions between Cd and the T1(Al2CuLi)andδ′(Al3Li)precipitates in Al-Li-Cu alloy are first reported.The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.

CO_2 Corrosion and Grooving Corrosion Behavior of the ERW Joint of the Q125 Grade Tube Steel

In order to investigate the CO2 corrosion behavior and the grooving corrosion susceptibility of electric resistance welded tubes of the Q125 grade, the high temperature and high pressure autoclave was employed to conduct CO2 corrosion experiments for the welded joint. The mechanisms of grooving corrosion and the factors influencing grooving corrosion susceptibility were identified by electrochemical measurement, microstructure observation, residual stress examination, micro-region composition and orientation analysis. The CO2 corrosion results show that the corrosion resistance of the base material is the best, followed by heataffected zone and the welded seam is the worst. The grooving corrosion occurred in the welded seam, and the grooving corrosion susceptibility of welded seam is relativity high. The dominated reason for the grooving corrosion of the electric resistance welded joint is the notable inclusions consisting of MnS as the main content in the welded seam. The proportion of high-angle grain boundaries in the welding zone is higher than that of base metal and the heat affected zone, which plays an important role in the corrosion behavior of the welded seam.

Initial nucleation of amorphous Si–B–C–N ceramics derived from polymer-precursors

Nucleation behavior of amorphous Si–B–C–N ceramics derived from boron-modified polyvinylsilazane procusors was systematically investigated by transmission electron microscopy(TEM) combined with spatially-resolved electron energy-loss spectroscopy(EELS) analysis. The ceramics were pyrolyzed at1000℃ followed by further annealing in N2, and SiC nano-crystallites start to emerge at 1200℃ and dominate at 1500℃. Observed by high-angle annular dark-field imaging, bright and dark clusters were revealed as universal nano-structured features in ceramic matrices before and after nucleation, and the growth of cluster size saturated before reaching 5 nm at 1400℃. EELS analysis demonstrated the gradual development of bonding structures successively into SiC, graphetic BNCxand Si3N4 phases, as well as a constant presence of unexpected oxygen in the matrices. Furthermore, EELS profiling revealed the bright SiC clusters and less bright Si3N4-like clusters at 1200–1400℃. Since the amorphous matrix has already phase separated into SiCN and carbon clusters, another phase separation of SiCN into SiC and Si3N4-like clusters might occur by annealing to accompany their nucleation and growth, albeit one crystallized and another remained in amorphous structure. Hinderance of the cluster growth and further crystallization was owing to the formation of BNCxlayers that developed between SiC and Si3N4-like clusters as well as from the excessive oxygen to form the stable SiO2.

Effects of metallic microstructures on fatigue fracture of Q345 steel

Effects of high-frequency cyclic loading on the banded ferrite-pearlite steel were analyzed through crack initiation and propagation. Interfaces of ferrite and pearlite colony with a small angle deviation from the loading axis were verified to be the most potential sites to fabricate the microcracks caused by the high strain gradient. The initial crack extension inside ferrite grain was driven by shear stress in model II along the direction with a 45° angle to the loading axis. Banded pearlite colony and the high-angle grain boundaries were considered as the dominant factors that promote the fatigue resistance of the material through arousing crack deflection in short crack propagation range and crack branching in long crack propagation range to reduce the crack propagation driving force in the crack tip. P-S-N curves were used to quantify the dispersion of fatigue lifetimes and evaluate the effect of elevated volume content of pearlite colony on the fatigue performance of the material.

Near-equiatomic high-entropy decagonal quasicrystal in Al20Si20Mn20Fe20Ga20

High-entropy alloys(HEAs)contain multiple principal alloying elements,but usually with simple crystal structures.Quasicrystals are structurally complex phases,but are generally dominated by only one element.However,nearequiatomic high-entropy quasicrystals have rarely been reported because they are difficult to prepare experimentally and predict theoretically.Therefore,the preparation and crystal structures of near-equiatomic high-entropy quasicrystals have drawn much interest.We report a quinary decagonal quasicrystal(DQC)with near-equiatomic alloying elements in Al20Si20Mn20Fe20Ga20 melt-spun ribbons,which is the first to our knowledge.Meanwhile,the structural features of the DQC are characterized in detail.The configurational entropy of both the alloy and DQC satisfies the entropy-based criterion for HEAs,suggesting a high-entropy DQC.Our findings provide a new strategy to develop high-entropy quasicrystals.

Microstructure and impact toughness of 16MND5 reactor pressure vessel steel manufactured by electrical additive manufacturing

Electrical additive manufacturing can improve manufacturing efficiency and reduce the cost of 16MND5 reactor pres-sure vessel steel. Impact tests were conducted to compare the impact toughness of 16MND5 steels manufactured by the electrical additive manufacturing and conventional forging, respectively. It is found that the impact toughness of electrical additive manufacturing specimen was slightly higher than that of conventional forging specimen. The characterizations of microstructure show that there were large ferrites and carbides in electrical additive manufacturing specimen. The fracture mechanisms of electrical additive manufacturing specimen were that microvoids or microcracks were prone to nucleate at the large ferrite/bainite interface and large carbide/bainitic ferrite interface, where the stress concentration was high. In addi-tion, the block size and high-angle grain boundaries played a vital role in hindering crack propagation of electrical additive manufacturing specimen, helping to improve the impact energy and leading to a low ductile–brittle transition temperature. The results suggest that the electrical additive manufacturing technology was an effective method to enhance the impact toughness of 16MND5 steel.

Atomic-resolution characterization on the structure of strontium doped barium titanate nanoparticles

Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade,the majority of the investigation was carried out in thin-film materials;therefore,the doping effect on nanoparticles remains unclear.Especially,doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled.In this work,we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),integrated differential phase contrast(iDPC)-STEM,and energy dispersive X-ray spectroscopy(EDX)mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles.Powder X-ray diffraction(PXRD)results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase,but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles.Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.