Electron Backscatter Diffraction Study Research Articles

The effect of annealing on micro-hardness of molybdenum single crystals

Molybdenum (Mo) crystals exhibit excellent mechanical properties such as high yield strength, high elastic modulus, very high melting point, and excellent corrosion resistance, making them a suitable choice for various industrial applications. The mechanical behaviour of these crystals has been investigated through tension, compression, and indentation experiments. The indentation experiments on annealed Mo single-crystal thin film show an increase in hardness with increase in annealing temperature from 400 °C–650 °C. However, it is not clear whether this behaviour is specific to the Mo thin films or these are applicable to the bulk samples of single crystals also. In order to address these issues, the Vickers indentation experiments are performed on as-received and annealed samples of (100) -, (110) -, and (111) -oriented Mo single crystals. The results show that the low-temperature annealing leads to an increase in micro-hardness by 9% for (100) oriented crystals. The x-ray diffraction (XRD), electron backscatter diffraction (EBSD) and energy dispersive x-ray spectroscopy (EDS) studies have shown that there is a drop in the number of dislocation sources or dislocation density ( ρ ) with no high-angle grain boundary formation or any microstructural changes or any oxide formation. This necessitates to enhance the applied stress required for significant yielding (or yield strength) which results in an increase in the hardness. Based on experimental observations, a hardening mechanism governed by dislocation annihilation during annealing has been proposed in the present study.

Electron backscatter diffraction (EBSD) study of elongatoolithid eggs from China with microstructural and parataxonomic implications

AbstractElectron backscatter diffraction (EBSD) has been widely used in recent studies of eggshells for its convenience in collecting in situ crystallographic information. China has a wide variety of dinosaur eggshells, although nearly none have been studied with this technique. Elongatoolithid eggs include many oogenera, although the microstructural differences of some were not highly appreciated, leading to several parataxonomic problems. In this paper, we surveyed seven elongatoolithid oogenera in China using EBSD in order to acquire more information about their microstructural variation. It is shown in this paper that in some elongatoolithid eggshells, scaly calcite grains that form the squamatic ultrastructure are not the only form of calcite in the continuous layer. Large columnar grains separated by high-angled grain boundaries and slender subgrains separated by radially arranged low-angled grain boundaries could exist in certain areas of the eggshells such as Macroolithus and Macroelongatoolithus. This paper discusses the criteria for identifying squamatic ultrastructure and proposes type I (rich in rugged high-angled grain boundaries) and type II (rich in both rugged high- and low-angled grain boundaries) squamatic ultrastructures. A pathological layer is found in Undulatoolithus pengi. An external zone is identified in the eggshell of Heishanoolithus changii, which does not support its position within the oofamily Elongatoolithidae. We argue that Paraelongatoolithus no longer belongs to Elongatoolithidae based on a combination of reticulated ornamentation, columnar continuous layer, and acicular mammillae. The high structural variation in elongatoolithid eggshells also implies that it may be inappropriate to relate all previous elongatoolithid eggshells to oviraptorosaurs and assume they are non-monophyletic.

Role of residual stress in the failure of HF-ERW welded tubes

High-frequency electric resistance welding is used for manufacturing hydro formable tubes. Tube forming and welding results in the formation of residual stress. The hole drilling technique was used to evaluate the residual stress of the welded tube. Tensile residual stress of varying magnitude was observed at different locations on the tube. The weld, heat affected zone was observed to have the highest residual stress as a result of phase transformation, forming and gradually reduced towards the parent material. The generated tensile residual stress led to failure of the tube during mechanical evaluation. Additionally, electron backscattered diffraction studies (EBSD) of the fusion line and the thermo-mechanically heat-affected zone were found to have goss and cube texture. These detrimental textures can lead to easy crack propagation in the presence of defects along the fusion line. A post-weld heat treatment (PWHT) was carried out to alleviate the tensile residual stress and alter the weld microstructure. PWHT helped transform the bainite in the weld to ferrite and pearlite. The inter-critical annealing significantly reduced the tensile residual stress along the circumferential direction resulting in improved formability.

Unraveling the effects of nano-grained microstructure on mechanical behavior, corrosion, and in vitro biocompatibility of 316L austenitic stainless steel

Nanograins are often beneficial in achieving better cytocompatibility for metallic implants. In this work, we have achieved grains from the micro to nano range in 316L austenitic stainless steel by a combination of cryo-rolling (50%, 70%, and 90% thickness reduction) followed by annealing (750–1000 °C for 2–20 min). The combined effect of grain refinement along with texture on its mechanical, corrosion, and in vitro cellular behavior was thoroughly investigated. Microstructural observations revealed nanograins formation (grain size = 144 nm) only for the 90CRA sample, whereas grain refinement in the micron range was observed for 0-70CRA samples. Electron backscatter diffraction (EBSD) studies showed fully austenitic structures for all the annealed samples while low Kernel Average Misorientation (KAM) values indicated strain-free microstructures. Orientation distribution function (ODF) maps showed the presence of strong γ-fiber (<111>||ND) and weak α-fiber (<110>||ND) in the 90CRA sample. The grain refinement led to an increase in the yield strength and ultimate tensile strength from 470.6 ± 16.21 MPa and 858.35 ± 31.82 MPa (0CRA) to 1662.06 ± 58.44 MPa and 2112.3 ± 51.62 MPa (90CRA), respectively. The potentiodynamic polarization study revealed that the corrosion rate of the 90CRA sample was about eight times less than that of the 0CRA sample. This was further corroborated by Mott-Schottky analysis, which showed a lowering of both acceptor and donor densities with the reduction in grain size. The evolution of a strong <111> texture during cryo-rolling contributed towards enhanced corrosion resistance of nano-grained 316L. Furthermore, grain refinement improved wettability, which in turn led to better cell proliferation and differentiation. At all culture days, MC3T3-E1 cell proliferation and differentiation were considerably higher for nano-grained 316L micron-sized counterparts. Thus, grain refinement to the nano range is an effective technique for the property enhancement of biomedical implants.

A combined EBSD and machine learning study of predicting deformation twinning in BCC Fe81Ga19 alloy

Compared to face-centered cubic (FCC) metals, body-centered cubic (BCC) metals demonstrate more intricate deformation behavior and microstructural characteristics because of the influence of intrinsic unstable stacking faults and defect structure. To investigate the unique phenomenon of deformation twinning in Fe81Ga19 alloy with BCC structure at moderate temperature and low strain rate, four twin nucleation models were constructed using a combination of electron backscatter diffraction (EBSD) technique and machine learning. These models are aimed to predict twin nucleation of grains and explore the relationship between twin nucleation and microstructural attributes. The study revealed that amongst the 235 grains analyzed during in-situ compressive deformation, 32 grains experienced twinning. Nine attributes influencing twin nucleation were selected and ranked according to their importance. Grain area, average image quality, neighboring grain count, and the Schmid factor of twinning systems exhibited significant influence on twin nucleation. Decision tree and tree ensemble (XGBoost) achieved 94% and 96% accuracy, respectively, on the test set, showcasing robust generalization capability. Due to the optimization of hyperparameters, support vector machine (SVM) and artificial neural network (ANN) exhibited outstanding performance. The ANN model achieved an accuracy of 97% and an F1 score of 0.91 on the test set, while the SVM model achieved an accuracy of 98% and an F1 score of 0.94, indicating superior performance. Furthermore, the study revealed that the twinning stress in Fe81Ga19 alloy exhibited weak responsiveness to temperature during deformation, and the intrinsic factors of grains were identified as crucial factors influencing twin nucleation.

In-situ observation of deformation-induced grain reorientation in 718 Ni alloy microlattices

Microlattices pose ample opportunity for constructing light weight structures for the automotive and aerospace industries. Laser powder bed fusion is an appealing technique to fabricate these structures because of its capabilities to process high-resolution complex architectured structures. In this work we explore the use of a 718 oxide dispersion strengthened alloy to create three microlattice structures designed in nTop, a straight bar, honeycomb and body-centered cubic (BCC) microlattice and investigate the effects of architectures on tensile behavior of the microlattices in a scanning electron microscope. The straight bar configurations deliver high strength but low ductility. The BCC lattices are highly deformable but soft. The honeycomb has an attractive combination of high strength and pronounced work hardening. Furthermore, electron backscattered diffraction studies revealed substantial crystallographic reorientation and grain refinement in the honeycomb lattice during deformation, in contrast to little crystal orientation change in the straight bar specimens. This study suggests that architectures play a significant role in the tensile behavior and deformation mechanisms in metallic materials.

Effects of carbon content on precipitate evolution and crack susceptibility in additively manufactured IN738LC

Hot cracking is a major bottleneck preventing the additive manufacturing community from adopting precipitation-strengthened nickel-base superalloys, such as the IN738LC. Prior literature demonstrates the beneficial outcome of increasing the carbon content within IN738LC to alleviate its hot cracking problem. However, the effect of carbon content on the gamma prime precipitation and grain recrystallization was not fully addressed. Here, we fabricated five sample sets of IN738LC with different carbon contents and subjected these samples to two separate heat treatment processes. The precipitate and grain evolution were monitored under the backscattered electron imaging and electron backscattered diffraction studies. While the carbon addition could assist in addressing the hot cracking problem, horizontal delamination cracks were detected during the fabrication of large samples when the overall carbon content was above 0.4 wt.%, highlighting the need for care when introducing carbon for the purpose of resolving hot cracking.

EBSD study of variant reorientation, texture, and twin formation in a martensitic NiTi alloy deformed in compression

Martensitic crystallography plays a vital role in the texture evolution and mechanical properties in Nickel-Titanium (NiTi) shape memory alloys when subjected to deformation. However, their microstructural changes during deformation are not well known and understood. In this study, we systematically investigate the stress-induced change of the microstructure of NiTi shape memory alloy under compression using the electron backscattered diffraction (EBSD) technique, and more specifically the variant reorientation, the evolution of textures, and the formation of twins. The EBSD maps reveal that upon strain the martensite morphologies shift from needle to block and their orientations are strongly reinforced along the loading axis. To quantify these microstructural changes, we used the Interaction Work (IW) associated with the lattice distortion of single variant, which provides a good fit with the experimental observation. A strong dependence of reorientation on the pre-textures of the parent B2 grains was also put in evidence. Other plasticity sources were confirmed such as dislocations and deformation twins. The calculations indicate that, for some specific orientations of parent grains, the active deformation twins could be easier for {011}M twin than that of (201¯)M deformation twin, whereas other orientations only favor the (201¯)M deformation twin.

Determining the habit plane for radial δ-hydrides in a textured zirconium-alloy tube under hoop tensile stress: A theory-experiment approach

The orientation of hydrides with respect to externally applied stress affects the susceptibility of Zirconium (Zr) alloy fuel cladding tubes to through-wall failure. Previous studies have mainly focused on the situation in the absence of external stress, with little attention paid to the situation under applied stress. Hoop tensile stress can cause the reorientation of hydride platelets from the circumferential to the radial direction in the radial textured Zr fuel clad tubes, substantially degrading its hoop ductility. In this study, we used a theory-experiment approach to investigate the radial hydride-matrix orientation relationship. A microstructure criterion was proposed to determine the habit plane of the radial δ-hydrides. Our results demonstrate that radial δ-hydrides predominantly form on the pyramidal 101¯1α plane of α-Zr with 101¯1α−Zr//111δ−hydride. The electron backscatter diffraction study of hydrided Zircaloy-4 tube provides experimental evidence supporting theoretical prediction. The underlying mechanism for this phenomenon is attributed to a competition between tensile stress-assisted hydride nucleation and strain-induced resistance to nucleation.

Lattice preferred orientation of quartz in granitic gneisses from Tso Morari Crystalline Complex, Eastern Ladakh, trans-Himalaya: evaluating effect of Dauphiné twin in dynamic recrystallization during exhumation

Abstract The Tso Morari Crystalline complex (TMCC) of eastern Ladakh, India, is part of the north Indian continental margin and is characterized by eclogitic enclaves embedded within ortho- and paragneisses known as the Puga Gneiss. Two fault zones bound the TMCC: the Karzok fault to the southwest and the Zildat fault to the northeast. In the present study, we carried out Electron Backscatter Diffraction study of quartz of 10 samples collected from the Puga Gneiss. The relict and recrystallized quartz grains were treated separately to understand the deformation conditions of the Puga Gneiss during early and late deformation stages related to UHP metamorphism and final stage of exhumation during retrogression, respectively. Microstructural observations suggest dynamic recrystallization in quartz and plagioclase at different temperature ranges. Misorientation analysis of both relict and recrystallized quartz grains reveals presence of Dauphiné Twins. Lattice preferred Orientation (LPO) of &lt;c&gt; axis of relict quartz grains generally shows more than one point maxima indicating that the relict grains preserve LPO developed during different stages of metamorphism/deformation. On the other hand, LPO of &lt;c&gt; axis of recrystallized grains from Karzok and Zildat fault zones shows asymmetric single girdle either normal or at an angle to the foliation plane, which suggests simple shear. We conclude that grain size reduction and recrystallization of the Puga Gneiss was greatly influenced by Dauphiné Twin and the final exhumation of the TMCC took place in a simple shear environment aided by activity along its two binding fault zones.

Griffinite, Al2TiO5: A New Oxide Mineral from Inclusions in Corundum Xenocrysts from the Mount Carmel Area, Israel

Griffinite (IMA 2021-110), ideally Al2TiO5, is a new mineral from inclusions in corundum xenocrysts from the Mount Carmel area, Israel. It occurs as subhedral crystals, ~1–4 μm in size, together with Zr-rich rutile within a corundum grain. In this study, a mean of eight electron probe microanalyses gave TiO2 44.41 (24), Al2O3 55.13 (18), FeO 0.47 (5), and MgO 0.37 (2), totaling 100.38 wt%, which corresponded, on the basis of a total of five oxygen atoms, to (Al1.97Mg0.02Fe0.01)Ti1.01O5. Electron back-scatter diffraction studies revealed that griffinite is orthorhombic and in the space group Cmcm, with a = 3.58 (2) Å, b = 9.44 (1) Å, c = 9.65 (1) Å, and V = 326 (2) Å3 with Z = 4. The six strongest calculated powder diffraction lines [d in Å (I/I0) (hkl)] are 3.347 (100) (110); 2.658 (90) (023); 4.720 (77) (020); 1.903 (57) (043); 1.790 (55) (200); and 1.688 (44) (134). In the crystal structure, Al3+ and Ti4+ are disordered into two distinct distorted octahedra, which form edge-sharing double chains. Griffinite is a high-temperature oxide mineral, formed in melt pockets in corundum-aggregate xenoliths derived from the upper mantle beneath Mount Carmel, Israel. The new mineral is named after William L. Griffin, a geologist at Macquarie University, Australia.

Effect of He Plasma Exposure on Recrystallization Behaviour and Mechanical Properties of Exposed W Surfaces—An EBSD and Nanoindentation Study

Fusion reactors are designed to operate at extremely high temperatures, which causes the plasma-facing materials to be heated to 500 °C to 1000 °C. Tungsten is one of the target design materials for the plasma-facing diverter components in Tokamak designs, such as ITER, because of its excellent high-temperature strength and creep properties. However, recrystallization due to high temperatures may be detrimental to these superior mechanical properties, while exposure to He plasma has been reported to influence the recrystallization behaviour. This influence is most likely due to the Zener effect caused by He bubbles formed near the surface, which retard the migration of grain boundaries, while at the same time modifying the surface microstructure. This paper reports a study of the effect of plasma exposure at different sample temperatures on the recrystallization behaviour of W at different annealing temperatures. The characterization after plasma exposure and annealing is pursued through a series of post-exposure annealing, followed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) characterization and nanoindentation to determine the mechanical properties. Here, it is shown that the hardness is closely related to the recrystallization fraction, and that the plasma exposure at a sample temperature of 300 °C slows down the recrystallization more than at higher sample temperatures of 500 °C and 800 °C. Atomic force microscopy (AFM) was subsequently used to determine any changes in pile-up height around the nanoindents, to probe any indication of changes in hardenability. However, these measurements failed to provide any clear evidence regarding this aspect of mechanical behaviour.

A large-volume 3D EBSD study on additively manufactured 316L stainless steel

Most microstructure characterization tools are based on the observation of two-dimensional (2D) sections through a material. The results allow, for microstructures with homogeneous and often equiaxed grain shapes, a sufficiently good interpretation of microstructure formation and materials properties. Such microstructures are typically recrystallized grains or homogeneously deformed grains in plastically deformed materials. In contrast, metal parts fabricated by additive manufacturing (AM) exhibit microstructures that differ significantly from classical materials as they frequently develop very heterogeneous and often nonregular grain structures. Orientation microscopy-based electron backscatter diffraction (EBSD) is probably the most quantitative materialographic technique for 2D microstructure characterization. By combination with serial sectioning the technique is extended to a powerful 3D characterization technique. Here we use a large-volume 3D EBSD system (ELAVO 3D) to analyze an AM-built 316L stainless steel sample. The results show unique “tree-like” grain morphologies and related textures. We highlight issues invisible when using 2D EBSD.

The Influence of Powder Particle Size Distributions on Mechanical Properties of Alloy 718 by Laser Powder Bed Fusion

Currently, metallic powders for laser powder bed fusion (LPBF) primarily come in two commercially available powder size distributions (PSDs): 15+/45− for non-reactive powders and 15+/63− for reactive powders. These powders are generally produced via gas atomization processes that create highly spherical particles with a Gaussian PSD. Because of the standard deviation within a Gaussian distribution, only small portions of the total product are used for LPBF applications. This screening process makes the other particle sizes a waste product and, thus, increases processing costs. The non-reactive 718 powder was printed with both the typical PSD of 15+/45− and a wider bimodal experimental PSD. Compared to conventional 718, the 718 alloys with bimodal PSD shows less than a 0.2% difference in density, and insignificant change in mechanical behavior. Electron backscattered diffraction studies revealed that grain sizes and morphology were similar between the two sample sets, but bimodal 718 alloy has a slightly greater degree of large grains. The study suggests that particles with wide or bimodal size distributions show promise in producing equivalent high-quality products without sacrificing mechanical properties.

A Conventional and High Resolution Electron Backscatter Diffraction (EBSD) Study of Stress Fields around Hydrides in Zircaloy-4.

A Conventional and High Resolution Electron Backscatter Diffraction (EBSD) Study of Stress Fields around Hydrides in Zircaloy-4.

Fracture Characteristics of Super Duplex Stainless Steel after Hot Tensile Testing

This study’s temperature range of hot tensile testing is 1000–1200 °C, which is consistent with ordinary industrial hot working temperatures. The fractography of super duplex stainless steel S32750 after hot tensile testing is investigated with Optical Microscopy and Scanning Electron Microscopy, and Electron Back-scatter Diffraction and Transmission Electron Microscopy study hot deformation behaviors of the necking area. The results reveal that ~1050–1150 °C is the optimal hot working temperature range regarding hot ductility and cracking sensitivity. The micro-voids nucleate at the ferrite-austenite interphase boundaries following the Kurdjumov-Sachs (K-S) or Nishiyama-Wasserman (N-W) orientation relationship at 1000 °C. Therefore, a quasi-cleavage fracture forms along the interphase boundaries. At the temperature range 1050–1150 °C, a uniform distribution of fracture surface is formed, and the highest Reduction in Area appears at 1150 °C. Dynamic phase transformation occurs with the formation of secondary austenite at ferrite grain boundaries at 1200 °C, which results in an intergranular fracture surface morphology.

Investigating build orientation-induced mechanical anisotropy in additive manufacturing 316L stainless steel

Build orientation-induced mechanical anisotropy is critical for additive manufacturing metals. To leverage the existing research on anisotropy between Z and X/Y build orientations, this work focuses on the anisotropic behavior within 2D planes. Therefore, tensile coupons of 316L stainless steel (316L-SS) were fabricated in five different build orientations (X, Y, XY45°, Z, and ZX45°) using the laser powder bed fusion process with a pulsed laser. Different characterization techniques at various length scales were employed to investigate the mechanisms of mechanical anisotropy. According to the electron back-scattered diffraction (EBSD) study, X and Y samples had a larger fraction of <001> and <110> grains, whereas XY45° coupons had a larger fraction of <111> grains along the tensile axis. In contrast, Z samples exhibited a dominant <110> texture parallel to the tensile axis. X-ray diffraction analysis revealed that all the samples had a single austenitic phase but different dislocation densities. The tensile results of all samples showed higher yield strength and comparable ductility with those in the literature. Among all the build orientations, XY45° coupons had the highest yield strength due to the large fraction of <111> grains oriented along the tensile axis and the highest dislocation density of 2.2 × 1015 m−2. In contrast, the highest ductility of Z samples was caused due to twinning-favored <110> crystallographic texture along the tensile axis. The onset and termination of different stages of strain hardening were mainly affected by the cellular sub-grain structure and crystallographic texture, as well as their interactions with dislocation generation and evolution. These findings indicated that crystallographic texture and dislocation density were the dominant contributions to the mechanical anisotropy followed by grain morphology.

Electron backscatter diffraction study on bonding and crack formation mechanism of laser cladding NiTi alloy on 316 substrate

NiTi alloy was prepared on 316 substrate by laser cladding with the aiming of clarifying the mechanism of crack formation and interface bonding. The intermediate layer generated in situ at the bonding surface possesses a low stress level. The high hardness brittleness caused by Fe element distributed along the molten pool boundary is the starting point of coating cracking, and the crack is transgranular fracture. The pole diagram shows that from the interface to the top of the coating, the preferred grain orientation varies from {100} to {110}, which benefit from the conversion of the maximum temperature gradient.

Inclusion of nano silicon particle in SS316L through LPBF and its responses on corrosion behaviour

In this research work, laser powder bed fusion (LPBF) based stainless steel 316L (SS316L) was fabricated and its corrosion behaviour was analysed for the oil-gas piping application. The Field Emission Scanning Electron Microscopy (FESEM) analysis of the LPBF SS316L specimen revealed the presence of 1–2 μm size honeycomb structure and 2–10 μm size tabular structures. Nano-size particles in the range of 100 nm–500 nm were formed between the two tabular cells as well as their boundary regions in the LPBF SS316L specimen. The energy-dispersive X-ray spectroscopy (EDS) analysis of the nanoparticle confirmed the presence of Si with a percentage of 1.4% along with 15.9% of Cr and 1.6% of Mo that have the characteristic of dispersion strengthening of the LPBF SS316L specimen. In addition, the δ-ferrite phase was observed in tabular structure boundaries and intercellular regions of solute in the LPBF SS316L specimen. Moreover, among the three crystallographic orientations {001}{101}and {111}, no domination behaviour was observed from the Electron Backscatter Diffraction (EBSD) study. The Transmission Electron Microscopy (TEM) analysis confirmed the presence of nano twin structures that had a span of several nm on the FCC austenite unit cell. These twins came under the {111} category twining that often occurred in FCC metals. A potentiodynamic polarization test was conducted on the LPBF SS316L specimen at five different time periods (i.e., 0, 7, 15, 34 and 56 h) and it was assessed that the 0 and 15 h immersion specimens exhibited superior corrosion resistance compared with other LPBF SS316L specimens. The Nyquist plot revealed that the 0 and 15 h immersion specimens offered the highest resistance value of 1846.1Ω and 1720.3 Ω, respectively against corrosion. The Bode plots of the LPBF SS316L specimen followed a similar trend as the Nyquist plots.

Microstructural and hardness homogeneity in an Mg–Gd−Y–Ag alloy processed by simple shear extrusion

An extruded Mg–6Gd−3Y−1.5Ag (wt%) alloy was processed by 1, 2, 4 and 6 passes of simple shear extrusion (SSE) at 553 K. Microstructural studies through electron back-scattered diffraction (EBSD) taken from the central areas of the cross sections normal to the extrusion direction (ED) exhibited microstructures mostly comprised of large severely deformed grains having high fractions of low angle grain boundaries (LAGBs) at the early stages of processing. By increasing the number of SSE passes, the fraction of fine grains, with an average size of 1.1 μm, developed through the occurrence of dynamic recrystallization (DRX), increased continuously. The highest recrystallization fraction of 72% was obtained after 6 passes. The EBSD studies on the cross section, however, showed that some degree of heterogeneity was still persistent after 4 passes of SSE along the path from the central areas towards the periphery of the specimen. This inhomogeneity in the microstructure seems to be resolved by increasing the SSE passes to 6. The micro-hardness measurements on the cross section normal to ED of the SSE-processed alloys showed a reasonable level of homogeneity after 6 passes while at the early stages of processing the hardness distribution was in its most heterogeneous state. Furthermore, the overall hardness values increased gradually from the average of 91.3 Hv for the single-pass processed alloy to 110.1 Hv for the one processed by 6 passes of SSE. This improvement in the average hardness was attributed to the Hall-Petch effect related to grain refinement, Orowan hardening as a result of Mg5Gd-type submicron-particles formed via dynamic precipitation, and substructure strengthening caused by the residual LAGBs.