Neighboring Grains Research Articles

{332} Twinning transfer behavior and its effect on the twin shape in a beta-type Ti-23.1Nb-2.0Zr-1.0O alloy

The interaction between twins and grain boundaries (GB) has an important influence on the deformation and fracture behavior of materials. In the present work, {332}<113> twinning transfer (TT) behavior and its effect on the twin shape in a deformed β-type Ti-23.1Nb-2.0Zr-1.0O Ti alloy were investigated experimentally and with molecular dynamics simulation. The crystallographic alignment factor of the two twinning systems in the neighboring grains and the misorientation angle of the grain pairs were found to influence the occurrence of TT. This further determines the twin shape: twins present a ruler shape when TT occurs but are in a lenticular shape otherwise. Such different twin shapes are attributed to the local stress states related to TT occurring or not. Both ruler-shaped paired twinning and lenticular twinning would provide effective mechanisms to release or reduce the stress concentration in front of the twin tips in different grain pairs.

A novel 3D mixed-mode multigrain model with efficient implementation of solute drag applied to austenite-ferrite phase transformations in Fe-C-Mn alloys

A computational 3D model that accounts for both nucleation and interface migration is a very useful tool to monitor and grasp the complexity of microstructure formation in low-alloyed steels. In the present study we have developed a 3D mixed-mode multigrain model for the austenite-ferrite and the austenite-ferrite-austenite formation capable of following diffusional phase transformations under arbitrary thermal routes. This new model incorporates the solute drag effect of a substitutional element (in this case Mn) and ensures an automatic change in transformation direction when changing from heating to cooling and vice-versa. An analytical solution for calculating the energy dissipation of solute drag together with multiple regression approximations for chemical potentials are proposed which significantly accelerate the computation. The modelling results are first benchmarked for an Fe-0.1C-0.5Mn (wt.%) alloy under different continuous cooling and isothermal holding conditions. The model revealed relatively large variations in transformation kinetics of individual grains as a result of interactions with neighboring grains. Then the model is applied to predict the transformation kinetics of a series of Fe-C-Mn alloys during cyclic partial phase transformations. The comparison with experimental dilatometer results nicely validates the predictions of this model regarding the change in overall transformation kinetics of the ferrite transformation as a function of the Mn content. New features of this model are its efficient algorithm to compute energy dissipation by solute drag, its capabilities of predicting the microstructural state for spatially resolved grains and the minimal fine tuning of modelling parameters. The code to implement this model is publicly available.

Coupled continuum damage mechanics and crystal plasticity model and its application in damage evolution in polycrystalline aggregates

In the present study, damage initiation and growth in a polycrystalline aggregate are investigated. In this regard, an anisotropic continuum damage mechanics coupled with rate-dependent crystal plasticity theory is employed. Using a thermodynamically consistent procedure, a finite deformation formulation is derived. For this purpose, the damage tensor is incorporated in the crystal plasticity formulation for a cubic single crystal. The damage evolution is considered to be dependent on the history of damage, equivalent plastic strain, stress triaxiality, and Lode parameters. This material model is implemented in the commercial finite-element code Abaqus/Standard by developing a user material subroutine (UMAT). Using the available experimental tests of 316L single crystal in the literature, the crystal plasticity hardening and damage parameters are calibrated considering the stress–strain curve before and after necking, respectively. The damage sites in a single-phase polycrystalline aggregate are also considered using a polycrystalline model consisting of grains with random sizes and orientations. The results show that the damage arises at the grain boundaries and triple junctions. Moreover, growth of the damage mostly occurs in the grains with higher Schmid factor compared to the neighboring grains. The presented model manifests capacity for determination of damage initiation sites and damage evolution in polycrystalline models.

Investigation of Relationships between Grain Structure and Inhomogeneous Deformation by Means of Laboratory-Based Multimodal X-Ray Tomography: Strain Accuracy Analysis

The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such distributions may be determined by the microstructural feature tracking method. However, the strain accuracy and the sources of uncertainty of this method are not well quantified yet. Evaluate the accuracy of local strain determination based on laboratory-based multimodal X-ray tomography measurements. The plastic deformation behavior of a particle-contained fully recrystallized Al-4mass%Cu alloy was characterized during in-situ tensile testing using absorption contrast tomography to reveal marker particles and diffraction contrast tomography to reveal the grain structure. It was found that the accuracy in strain measurement is inversely proportional to the particle distance, whereas it is independent of the particle size, and the accuracy is not biased by grain boundaries. As an illustrative example, the preliminary analysis of the microstructure-strain relationships reveals significant strain differences both between and within individual grains. The results document the validity and limitations of the microstructural feature tracking method for local strain measurements using a laboratory X-ray source, are of importance for local strain analysis in general and may be considered as an alternative to other methods, e.g. digital image correlation. The measurements allow evaluation of effects of the grain microstructure on the local strain development during plastic deformation. By a preliminary analysis of the strain difference between two selected grains, it is suggested that the grain shape and crystallographic relationships between neighboring grains are of importance for the development of local strains.

The 3D graph approach for breakdown voltage calculation in BaTiO3 ceramics

After pioneering attempts for the introduction of graph theory in the field of ceramics and microstructures, where 1D and 2D graphs were used, in this paper we applied 3D graphs for the breakdown voltage calculation in BaTiO3 sample with some predefined constraints. We have described the relations between grains in the sample and established a mathematical approach for the calculation of breakdown voltage using experimental results. As a result, we introduced mapping between the property of sample and grain structure, then between the grain structure and mathematical graph, using various crystal structures. The main idea was to apply 3D graph theory for the distribution of electronic parameters between the neighboring grains. With this study, we successfully confirmed the possibilities for applications of graphs as a tool for the determination of properties even at the intergranular level.

Formation of abnormal nodular ferrite with interphase precipitation in a vanadium microalloyed low carbon steel

Abnormal nodular ferrite (NF) with vanadium carbide (VC) interphase precipitation was observed in a vanadium-microalloyed low carbon steel. The NF is characterized as a structure with a high density of low-angle boundaries, having an irrational ferrite/austenite orientation relationship (OR) with angular deviation of 15-30 ° from the exact Kurdjumov-Sachs OR with its neighboring austenite grain into which it grows. The growth of NF is substantially faster than that of normal grain boundary ferrite in the same alloy. Even in one single NF, the formation of multiple variants of VC interphase precipitation was confirmed, each of which was bordered by low-angle boundaries.

Texture Formation in Polycrystalline Thin Films of All-Inorganic Lead Halide Perovskite.

Controlling grain orientations within polycrystalline all-inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits; however, the forces governing texture formation are ambiguous. Using synchrotron X-ray diffraction, mesostructure formation within polycrystalline CsPbI2.85 Br0.15 powders as they cool from a high-temperature cubic perovskite (α-phase) is reported. Tetragonal distortions (β-phase) trigger preferential crystallographic alignment within polycrystalline ensembles, a feature that is suggested here to be coordinated across multiple neighboring grains via interfacial forces that select for certain lattice distortions over others. External anisotropy is then imposed on polycrystalline thin films of orthorhombic (γ-phase) CsPbI3- x Brx perovskite via substrate clamping, revealing two fundamental uniaxial texture formations; i)I-rich films possess orthorhombic-like texture (<100> out-of-plane; <010> and <001> in-plane), while ii) Br-rich films form tetragonal-like texture (<110> out-of-plane; <110> and <001> in-plane). In contrast to relatively uninfluential factors like the choice of substrate, film thickness, and annealing temperature, Br incorporation modifies the γ-CsPbI3- x Brx crystal structure by reducing the orthorhombic lattice distortion (making it more tetragonal-like) and governs the formation of the different, energetically favored textures within polycrystalline thin films.

Effect of binary additives in mixed 2D/3D Sn-based perovskite solar cells

Additive doping improves the morphology and stability of tin (Sn)-based perovskite films under ambient conditions. However, the role of additives in the perovskite layer is not clearly understood, especially when two or more additives are incorporated. In this study, the effect of binary additives composed of 2-phenylethylammonium iodide (PEAI) and ethylenediammonium diiodide (EDAI2) on formamidinium tin iodide (FASnI3) perovskite solar cells (PSCs) is studied. PEAI plays an important role in reducing the dimensionality of the perovskite crystals from 3D to mixed 2D/3D, whereas EDAI2 resides on the grain periphery as a linker to improve the interconnection between neighboring grains. Overall, the optimum blending of the two additives, 8 and 1 mol % of PEAI and EDAI2, produces pinhole-free, compact perovskite film with superior crystallinity and preferential orientation, exhibiting very low background charge carrier density, reduced trap states and suppressed recombination losses. The reduced dimensionality and favored perovskite layer stacking lead to a better interlayer coupling that improves charge transfer at the interfaces. Consequently, the best PSC exhibits a power conversion efficiency (PCE) of 8.47% with an open-circuit voltage (VOC) of 0.634 V and the device stability is enhanced up to 5 days in ambient conditions without any additional encapsulation.

Atomistic simulation of grain boundary migration induced by non-equilibrium solute distribution

While atomistic simulation is now a widely used method for investigating grain boundary migration, it is usually based on the so-called artificial driving force. In this study, we report a new general atomistic method for simulating grain boundary migration based on a tunable physical driving force that is induced by unbalanced solute distribution. This is motivated by the previous experimental reports that non-equilibrium distribution of solute atoms, e.g., solute atoms are more enriched/depleted in one grain relative to the other, is commonly observed during diffusion induced grain boundary migration. We show that the solute-induced driving force caused by the unbalanced free energy in the two neighboring grains strongly depends on the type of the solute atoms, which can be used to tune both the type (e.g., attraction or repulsion) and magnitude of the driving force. Furthermore, we find that different solute types (with varying atomic size and cohesive energy) interact with the grain boundary in different ways resulting in solute segregation or anti-segregation. Moreover, the lattice strain resulting from atomic size mismatch, which has been proposed to be an important driving force for diffusion induced grain boundary migration, is found to be not always needed to induce the grain boundary migration. We hope that while this study showcases a new atomistic method of simulating grain boundary migration, the results of this investigation also aids the understanding of the phenomenon of diffusion induced grain boundary migration, for which clear physical mechanisms remain elusive after decades of research.

Graph theory applied to microelectronics intergranular relations

The focus of this study is on the control of layers between grains by applying graph theory. We performed modification of BaTiO3 nanoparticles with Y2O3. The results of capacitance change on submicron level are the part of the measured values on the bulk samples. The original idea is to develop the new approach to use graph theory for networking of electronic parameters between the neighboring grains in order to compare the values measured on the sample, and to present them through the edges in graph between corresponding vertices. Capacitance change with DC bias was measured on bulk samples, and the modified nanoparticles showed stability up to 90 V. After using graph theory with the different number of neighboring grains and on different voltages, it has been shown that capacitance change can be successfully calculated on the layers between grains. Original calculations presented as 1D cases were performed, confirming graph application as a tool with which measured bulk results can be downsized to an appropriate intergranular level, opening the new perspectives in the area of miniaturization and micropackaging.

MULTILEVEL PHYSICAL-ORIENTED MODEL: APPLICATION TO THE DESCRIPTION OF THE INITIAL STAGE OF DYNAMIC RECRYSTALLIZATION OF POLYCRYSTALS

Thermomechanical processing of metals and alloys is accompanied by deep changes of the material structure (including grain structure), which determines physical and mechanical properties and the working characteristics of products made from them. Its change is possible due to mechanical (fragmentation process) and/or temperature (recrystallization process) influences. Because of this, an urgent task is to create mathematical models that allow describing changes in the material structure and the stress-strain state under thermomechanical treatment. For this purpose, the multilevel physically oriented model was developed for researching inelastic deformation of polycrystals. The problem of modeling two stages deformation of a polycrystalline copper sample was formulated. At the first stage, preliminary cold intense plastic deformation under complex loading was investigated. Two variants of preliminary deformation were considered. They were homogeneous deformation corresponding to equal-channel angular compression (ECUP), and deformation with closed deformation trajectory. At the second stage, uniaxial high-temperature deformation was considered prior to the beginning of an intensive dynamic recrystallization. The paper describes the method for estimating the recrystallized material volume fraction within the framework of the multilevel model. The influence of the deformation temperature, the preliminary deformation, the deformation texture, and the average angle of mutual misorientation of neighboring grains on recrystallization was investigated. These parameters determine the development of dynamic recrystallization, since its main physical cause is the difference in stored energy between neighboring grains. It was shown that the developed mathematical model is suitable for describing the thermal activation of dynamic recrystallization at temperatures in the range of 0,4–0,7 homologous temperature. The deformation trajectory complexity determines the type of deformation texture, its “sharpness” or “dispersion”, the angles of neighboring grains mutual misorientation. The results of computational experiments are presented. According to the proposed method, the deformation at the high-temperature stage is determined, at which the intensive migration of new grains begins during recrystallization.

Deformation of Aluminum in Situ Sem and Full Field Measurements by Digital Image Correlation: Evidence of Concomitant Crystal Slip and Grain Boundary Sliding

Mechanical testing in situ scanning electron microscopy (SEM) has become a current technique for multiscale micromechanical investigation of polycrystalline materials, because direct observation of deformation microstructures allows identification of strain heterogeneities and related mechanisms. Yet, most of the studies are based on the inherited post mortem microstructures, thus precluding to unravel the local loading history, to understand the development of localization patterns, the potential interactions of concomitant mechanisms and to quantify their respective contributions to the overall strain. We therefore developed a novel experimental setup for thermomechanical testing in situ SEM, especially suited for full strain field measurements based on digital image correlation (DIC) from the sample scale, to the scales of the aggregate and the single grain. We present results obtained during simple compression, at controlled displacement rate and at temperatures up to 400°C, for polycrystalline aluminum presenting randomly oriented coarse grains (ca. 300 m in size). According to the different scales of interest, specific surface marking patterns were realized by electron microlithography. Kinematic analysis by digital image correlation (DIC) allowed to retrieve full surface strain fields. The latter evidenced that the overall viscoplastic response was dominated by crystal slip plasticity. Increasing temperature favored the activation of non-octahedral slip, but also substantial and continuous contribution of grain boundary sliding (GBS). We suggest the latter mechanism as necessary to accommodate local plastic incompatibilities between neighboring grains.

Влияние кремния на свойства спечённых сплавов системы (Al – Si) – Sn

Structural features of composites of the (Al – xSi) – 40Sn system prepared by liquid-phase sintering of mixtures of tin powder of PO 2 grade with powders of Al – Si alloys of hypoeutectic, eutectic, and hypereutectic composition were studied in this work. Samples were cut from the prepared materials for compression test and dry friction test against steel according to the “pin-on-disk” scheme. It was established that the main structural elements of the sintered composites are determined by the nature of interaction of solid silumin particles and liquid tin. This is due to the fact that tin not only spreads over the volume of the sintered compact, but also activates the processes of recrystallization of aluminum powders due to dissolution of their atoms in the liquid phase with subsequent deposition on the large particles surface. The dissolution weakens the skeleton of aluminum powders, and they are able to regroup into a denser configuration under the action of capillary forces. It was found that silicon inhibits the shrinkage of the compacts during the liquid-phase sintering. Therefore, to improve the mechanical properties of the sintered composites, they should be subjected to additional densification in order to eliminate their residual porosity, which simultaneously contributes to a significant increase in their wear resistance under dry friction. The study of the wear features of the (Al – хSi) – 40Sn composites was carried out. It was found that silicon particles located in the tin interlayers hinder the relative shear of the neighboring matrix grains and increase the thickness of the surface layer involved in deformation by friction forces. This fact has a favorable effect on the wear resistance of the investigated sintered composites under dry friction process. The (Al – 12Si) – 40Sn composite sample with the eutectic matrix has the highest wear resistance.

Polycrystal Simulation of Texture-Induced Grain Coarsening during Severe Plastic Deformation.

During severe plastic deformation (SPD), there is usually extended grain fragmentation, associated with the formation of a crystallographic texture. The effect of texture evolution is, however, coarsening in grain size, as neighbor grains might coalesce into one grain by approaching the same ideal orientation. This work investigates the texture-induced grain coarsening effect in face-centered cubic polycrystals during simple shear, in 3D topology. The 3D polycrystal aggregate was constructed using a cellular automaton model with periodic boundary conditions. The grains constituting the polycrystal were assigned to orientations, which were updated using the Taylor polycrystal plasticity approach. At the end of plastic straining, a grain detection procedure (similar to the one in electron backscatter diffraction, but in 3D) was applied to detect if the orientation difference between neighboring grains decreased below a small critical value (5°). Three types of initial textures were considered in the simulations: shear texture, random texture, and cube-type texture. The most affected case was the further shearing of an initially already shear texture: nearly 40% of the initial volume was concerned by the coalescence effect at a shear strain of 4. The coarsening was less in the initial random texture (~30%) and the smallest in the cube-type texture (~20%). The number of neighboring grains coalescing into one grain went up to 12. It is concluded that the texture-induced coarsening effect in SPD processing cannot be ignored and should be taken into account in the grain fragmentation process.

In-Operando Nanoscale X-ray Analysis Revealing the Local Electrical Properties of Rubidium-Enriched Grain Boundaries in Cu(In,Ga)Se2 Solar Cells.

Chalcogenide Cu(In,Ga)Se2 solar cells yield one of the highest efficiencies among all thin-film photovoltaics. However, the variability of the absorber compositions and incorporated alkali elements strongly affect the conversion efficiency. Thus, effective strategies for spatially resolved tracking of the alkali concentration and composition during operation are needed to alleviate this limitation. Here, using a hard X-ray nanoprobe, we apply a synergistic approach of X-ray fluorescence analysis and X-ray beam-induced current techniques under operando conditions. The simultaneous monitoring of both compositional and functional properties in complete solar cells illustrates the exceptional capabilities of this combination of techniques in top-view geometry, where high spatial resolution resulted even underneath the electrical contacts. Our observations reveal Rb agglomerations in selected areas and compositional variations between different grains and their boundaries. The concurrent detection of the functionality exhibits negligible effects on the collection efficiency for Rb-enriched grain boundaries in comparison to their neighboring grains, which indicates the passivation of detrimental defects.

Heat diffusion in numerically shocked ordinary chondrites and its contribution to shock melting

High pressure shock metamorphism in ordinary chondrites involves heating and melting of individual phases from shock entropy, pore collapse, frictional heating, and heat transfer. Numerical models using shock physics codes have recently been used to comprehend the mechanism of shock heating and melting in multiphase mesoscale models. Such models suggest that the formation of sulfide and metal melt veins in ordinary chondrites (shock-darkening) can be explained by preferential heating and melting of iron and iron sulfides during shock. However, those models usually dismissed heat transfer between heterogeneously shock heated phases. This leads to an underestimation of the degree of melting in phases that experienced low degrees of shock heating (e.g. iron metal) but are in direct contact with strongly shock heated phases (e.g. iron sulfides). In our study, we implemented a finite difference 2-D heat diffusion code to model heat diffusion among neighboring grains in shock heated multiphase meshes that represent typical textural relations of silicate, sulfide and metal grains in ordinary chondrites. Post-shock temperature maps for each textural model were calculated using the iSALE shock physics code and used as input for the diffusion code. We find that heat diffusion, not initial shock heating, is the principal cause for heating and melting of metals in eutectic contact with iron sulfides at ~50 GPa of pressure. In addition we study the effects of iron and troilite grain sizes, shock pressures and pre-shock porosities of the silicate matrix, and discuss the preservation of melt allowing melt migration in shock-darkened meteorites and the observation of metal-silicate intermixed melting. With our work, we demonstrate that the consideration of heat diffusion during and after shock is crucial for a better understanding of melting features in both experimentally and naturally shocked ordinary chondrites.

Вплив розміру зерна в полікристалічних матеріалах на механізми пластичної деформації та границю плинності

The influence of grain size on the physical yield strength of the polycrystal is considered by the method of cellular automata. The physical yield strength of the polycrystal in this model is defined as the stress at which, the plastic deformation covers the entire cross section of the sample from one edge to another. Three mechanisms of plastic deformation are considered. The first one is an initiation of plastic flow from grain to grain by dislocation pile-ups. The second one is plastic flow in different grains independently of each other under the action of external stress and the third one is intergranular slippage. Computer simulations have shown that at large grain sizes (d &gt; 200 nm) deformation propagates from grain to grain by initiating dislocations pile-ups, since in this case pile-ups are quite powerful and have a large effect on neighboring grains. At average values of grain size (20 nm &lt;d &lt;200 nm) plastic deformation occurs in the grains independently of each other, and the external strain give a major influence on plastic deformation. With further reduction of the grain sizes (d &lt;20 nm) the main mechanism of deformation is intergranular slippage. because in grains of this size are quite large image stresses that do not allow large dislocation clusters. In small grains the image forces are quite large to prevent large dislocation pile-ups formation, but the mass and volume of grain are quite small to turn or slip its under the action of external stresses. In accordance with these mechanisms, on the calculated dependence of the physical yield strength vs grain size, there are three areas with different angles of inclination in logarithmic coordinates. Keywords: yield point, grain size, Hall―Petch low.

Crystal Plasticity Finite Element Method for Slip Systems Evolution Analysis of α/β Duplex Titanium Alloys during Quasi-Static Tensile Testing

The crystal plasticity finite element method, modeled on a realistic microstructure image, was developed to investigate the evolution of slip systems in grains of α/β titanium alloys during quasi-static tensile testing. By analyzing the data of slip evolution of simulation during the overall plastic deformation process, it was found that the prismatic slip systems in the α phase and the {112} &lt;111&gt; slip systems in the β phase played a leading role. By calculating the Schmid factors, it was found that the values calculated from the local stress, which was represented by major principal stress, were larger than the values calculated from the primary uniaxial tensile direction, which was due to the deviation of the local stress direction from the primary uniaxial tensile direction. Furthermore, the deviation of local stress of α phase was different from that of β phase, which was related to the deformation mechanism. During the deformation, the stress and strain were concentrated in the grains of the α phase, producing a driving effect on the neighboring grains of the β phase. Subsequently, the incompatible deformation produced the concentration of strain at the grain/interphase boundary, thus strengthening the grain interactions and leading to the deviation.

Effect of Martensitic Transformation and Grain Size on the Surface Roughening Behavior in SUS 304 and SUS 316 Thin Metal Foils

The surface roughening and martensitic phase transformation (MPT) of SUS 304 and SUS 316 were studied through two experiments: a uniaxial tensile stress test, repeated for five cycles, and an Scanning Electron Microscope–Electron Backscaterr Diffraction (SEM-EBSD) investigation. The MPT and martensitic volume fraction (Mf) were evaluated following the tensile test. The correlation between MPT, Mf, and surface roughening behavior was investigated. The experiment showed that an increase in the strain level from 0.4% to 1% increased the MPT and Mf, which transformed from a metastable austenitic phase in SUS 304. The increased strain level increased the surface roughening for various grain sizes (Dg), from fine grain (Dg &lt; 3 μm) to coarse grain (Dg ≥ 3 μm). SUS 304 and SUS 316 are used so that the surface roughening mechanism between SUS 304 and SUS 316, with different phase conditions and at a similar Dg, can be determined. The results showed that the surface roughening increased for both fine and coarse grain at strain levels of 0.4% and 1%; however, a larger increase of surface roughening was obtained for coarse grain. In coarse grain, surface roughening increased significantly not only with a low MPT, but also with a low grain deformation. In coarse grain, the surface roughening increased proportionally to the strain level (εp) because of the low MPT and weak grain. In fine grain, the surface roughening did not increase proportionally to the εp because of the high MPT, which increased the grain strength in SUS 304. In the fine grain of SUS 304, the increase of surface roughening was nearly the same both at strain levels of 0.4% and 1%, because the MPT and Mf were nearly the same. The surface roughening with the same εp and almost the same Dg in SUS 304 and SUS 316 fine grain was nearly the same, because the grain deformation almost produced the same relative inclination between neighboring grains in the initial state direction to the surface. The inter-grain movement changed the grain orientation. Based on kernel average misorientation (KAM) mapping, the local grain misorientation in SUS 304 was higher than that in SUS 316. This indicated that the fine-grain SUS 304 is harder than the fine-grain SUS 316. There is no MPT in SUS 316 because of the higher austenitic phase, which is affected by the austenitic former, such as Ni.

Crystallization behavior and mechanical response of metallic glass induced by ion irradiation at elevated temperature

When exposed to heavy-ion radiation, metallic glasses (MGs) often exhibit an excellent irradiation tolerance at room temperature compared with their crystalline counterparts; however, their structural evolution and mechanical response at elevated temperature is largely unknown. Here, the phase stability and crystallization behavior of ZrTiHfCuBeNi MG were investigated by irradiating it with an 8.0 MeV Xe29+ ion beam at 550°C. Nanocrystal precipitation randomly appeared in the MG matrix at low fluences, which overlapped and aggregated at higher fluences. In addition, non-edge-on faulted dislocations were formed between neighboring grains due to irradiation-induced stress. Moreover, delays in the first pop-in events after irradiation were attributed to irradiation-induced structural rearrangement and the precipitation of nanocrystals. This work sheds light on the structural evolution and mechanical properties of MGs when irradiated at elevated temperature.