An in-situ fatigue testing device, equipped in scanning electron microscope (SEM) and designed for long-time high temperature and complex stress testing conditions, was developed. The fatigue crack initiation and propagation behavior of notched Nickel-based single crystal superalloy (Ni-SX) was studied using the fatigue device combined with optimized speckle preparation. The mechanisms of crack initiation and propagation were analyzed using digital image correlation (DIC) and crystal plasticity finite element (CPFE) analysis. The results showed that fatigue crack initially formed at the notch root and propagated in mode II under the influence of the local stress distribution. As the stress field changed with fatigue, the crack propagation transitioned into a mixed mode. The micro in-situ high-temperature fatigue device and methodology are essential for studying low-cycle fatigue and local stress distribution in superalloys, especially under high-temperature conditions.

Despite the high energy density, inherent safety and cost-effectiveness of Lithium manganese iron phosphate (LMFP) cathode material, the mechanisms underlying the cycling degradation of LMFP-based batteries in automotive applications remain unclear. In this study, we conducted multi-scale analyses to further investigate and elucidate the causes of degradation. Electrochemical performance characterization such as discharge curves and electrochemical impedance spectroscopy (EIS) identified cathode degradation as the predominant contributor to capacity fade, where Jahn-Teller distortion at Mn3+sites induced lattice strain, propagating electrode cracks and Mn dissolution during cycling. Mn dissolution triggers elemental redistribution within cathode particles, as evidenced by altered Mn/Fe ratios in EDS mapping. Concurrently, it induces phase transformation within particles, with lithium-deficient phases confirmed through XRD and XPS analyses. Atomic-scale TEM characterization further identifies lattice defects, including vacancies. ICP analysis is employed to quantify a portion of dissolved manganese deposited on the anode surface, irreversibly consuming active lithium via SEI reconstruction, thereby expanding lithium-depleted regions in cathode particles. The combined degradation mechanism involving cathode compositional/structural alterations and anode SEI reformation-induced active lithium loss, ultimately manifests as anomalous voltage plateaus in electrochemical profiles. These cascading effects demonstrate a coherent degradation pathway, providing actionable insights for optimizing LMFP durability in high-energy automotive batteries through structural stabilization and compositional balancing strategies.

In order to clarify the deformation mechanism of Inconel 718 (IN718) alloy at the grain scale during tensile deformation, the deformation behaviors of IN718 alloy were investigated at 650 °C using an in situ electron backscatter diffraction (EBSD) tensile testing method. The evolution of grain morphology, crystallographic orientation, activated slip systems, grain boundaries evolution, and strain-induced misorientation were systematically analyzed during the tensile test. The results showed that the grains were elongated along the tensile direction, and the grain boundaries also became significantly curved. Meanwhile, the EBSD studies illustrated that the changes in local misorientation within individual grains were non-uniform and generally began at the grain boundaries. The low-angle grain boundaries (LAGBs) were first formed near the high-angle grain boundaries (HAGBs) and gradually expanded into the interior of the grains. The activation of the slip system and the Schmid factor were characterized and calculated based on the slip traces on the deformed grain surface. The evolution of local strain within the grains was evidenced by a kernel average misorientation (KAM) map. Finally, the plastic deformation mechanism at the grain scale was discussed in detail based on our experimental results.

Nickel-based superalloys are designed for high-temperature applications and exhibit micro- deformation mechanisms distinct from those observed at room temperature (RT). This paper investigated the microstructure, mechanical properties and deformation behaviors of laser powder bed fusion (LPBF) GH3536 alloy at RT, 750 degrees C and 815 degrees C using in-situ scanning electron microscopy (SEM) micro-tensile tests combined crystal plasticity finite-element simulation. The results show that as-built LPBF GH3536 alloy presents dendrite microstructure with plenty of processing cracks and pores. Anisotropic mechanical properties were observed, with higher strength in the laser scanning direction and greater elongation to fracture in the building direction. As the temperature rises, both strength and elongation to fracture decrease, with the rate of decline gradually accelerating. The processing defects, such as pores and microcracks, are the main reason for the crack initiation and fracture during tensile. The existence of melt pool boundaries (MPBs) and dendrite boundaries are responsible for the crack propagation. At high temperatures, low dislocation density reduces the bonding strength of MPBs and GBs, causing the deformation behavior of the LPBF GH3536 alloy shift from ductile at RT to brittle fracture at elevated temperature (ETs).

TA15 alloy, widely utilized in the aerospace industry for its exceptional mechanical properties, was examined in this study for its anisotropic microstructure evolution and deformation behavior in laser melting deposition (LMD)-fabricated samples at room temperature. Specimens were extracted from build (Z-) and scanning (X-) directions and their microstructures and mechanical properties were compared. A method based on in-situ electron back scattered diffraction (EBSD) tensile testing, was used by inserting a tensile stage into scanning electron microscopy (SEM) to observe the real-time microstructure evolution with the change of dynamic tensile force. The evolution of slip bands, grain rotation, grain-to-grain misorientation, and the dynamic change of mechanical properties were also systematically investigated. The results demonstrated that the anisotropic mechanical properties along the Z- and X-directions in LMD-fabricated TA15 alloy stemmed from variations in microstructural anisotropy. Z-direction specimen exhibits high elongation and reduction of cross section, whereas, high tensile strength and yield strength were identified in X-direction. Furthermore, the texture behavior, crack propagation and fracture mechanism are discussed for each specimen orientation.

Grain boundary engineering, achieved by combining annealing and surface coating, is an effective strategy for modifying high-nickel-layered oxide cathode materials. However, high-temperature annealing can induce irreversible phase transformations in high-nickel materials, which significantly hinder lithiation/delithiation and degrade their electrochemical performance. In this study, we propose a grain boundary engineering approach for LiNi0.83Mn0.05Co0.12O2, combining rapid heating to the annealing temperature with atomic layer deposition (ALD) to enhance its electrochemical properties. Compared to conventional heating, the rapid heating process minimizes Li/O loss and prevents the formation of a disordered phase. More importantly, grain boundary modification and bulk gradient doping effectively reduce large cracks and the erosion of the cathode, which slows down the capacity decay during long cycles. The direct heating sample exhibits a significant improvement in capacity retention, and after stable cycling for 300 times at C/3, the capacity retention rate remained at 84.7%. This approach offers a promising low-cost strategy for the development of advanced cathode materials with enhanced cycling stability.

The LPBF IN718 superalloy has great potential for aerospace applications. However, it faces challenges in large residual stress and brittle Laves phases leading to premature failure of the material. Improving the mechanical properties through heat treatment is a general approach. This study investigated the effect of solution heat treatments on the microstructure and mechanical properties of LPBF IN718 alloy. The alloy was heated under 980 degrees C, 1020 degrees C, and 1080 degrees C for 1 hour, followed by air cooling. Microstructural evolution, including grain size, cellular structure, Laves phase, delta phase, and annealing twins, was quantitatively analyzed using SEM, EBSD, and TEM. The tensile results show that the as-built samples have excellent tensile strength with an ultimate tensile strength of 1121 MPa and a yield strength of 887 MPa. The sample after solution heat treatment at 1080 degrees C shows the highest plasticity, which is 46.4 %. Theoretical calculations show that the high yield strength mainly results from the strengthening effect of the cellular structure, which can be regarded as a combination of dislocation and elemental segregation strengthening. The plasticity of the alloy increases with the increasing degree of recrystallization. The elimination of Laves phases and the formation of annealing twins are the key factors to the enhanced plasticity observed in the samples after solution heat treatment at 1080 degrees C.

In this study an intricate examination, comparing various samples, has been conducted to elucidate the impact of post-heat treatments on both microstructural characteristics and mechanical properties undergoing deformation. The initial microstructure of Laser direct melting deposition (LDMD) TA15 is strategically tailored into a dual-phase arrangement of lamellar α and β phases through diverse thermal processing methods conducted both above and below the β‐transus temperature. It is crucial to analyze how their deformation behavior varies post-annealing. HT1 exhibited diminished strength and restricted plasticity before fracturing, contrasting with HT2 and HT3. HT2 displayed inferior strength yet superior plasticity pre-fracture compared to HT3. Conversely, HT3 showcased elevated strength yet less plasticity. Thermal treatment at 950 °C offers the desired amalgamation of strength and ductility. The analysis of fracture morphology revealed a direct correlation between the duration of heat treatment and the augmentation in both the size and depth of dimples accompanied by the necessary levels of ultimate tensile strength.

The hub and web of turbine disk generally work below 600 °C and are prone to fatigue deformation. However, the rim typically operates at temperatures ranging from 550 to 700 °C, even occasionally exceeding 800 °C. Thus, the present study aims to investigate the tensile deformation behaviors of the rim region of Inconel 718 alloy turbine disk in the range of 650–850 °C, using an in situ high-temperature tensile stage. The results indicate that temperature has different effects on the tensile deformation behavior of alloy. The in situ observations revealed that the deformation at 650 °C was dominated by crystal slip. The microcracks mostly initiated near non-metallic inclusions (NMIs) and propagated in transgranular manner. Intergranular cracking appeared at 750 and 850 °C, but did not coalesce to form continuous intergranular cracks. Fractographic analysis demonstrated that the fracture mode was transgranular ductile fracture for the three temperatures. The voids on the fracture surface evidenced that the cracking and debonding of NMIs were the origins of most macroscopic cracks of the specimens. This study provided direct experimental evidence for revealing the deformation and damage mechanisms of the rim region of turbine disk at service temperature.

Microstructures significantly influence the physical properties of materials. Characterizing the evolution of materials' microstructures is helpful for exploring the processing techniques and understanding the thermodynamic properties of materials. However, the in-situ experiments based on the scanning electron microscope (SEM) often suffer from non-uniform image drift distortion, which severely interferes with the imaging and characterization. Therefore, in this study, we develop an external scanning and imaging system for dynamic image drift compensation during the in-situ SEM experiments. The drifted image was dynamically corrected to the center of view by changing the path of the electron beams. The proposed method was compared with three conventional image correction methods to validate its effectiveness in two scenarios, i.e., in-situ translation experiment and in-situ heating experiment. The results showed that the image registration technique combined with the electron beam trajectory correction effectively compensated the image drift caused by irregular sample motion. Compared with existing image post-processing methods, we have achieved real-time drift compensation of the images. For the secondary electron (SE) image with a resolution of 1024 × 1024 pixels compensated based on the method proposed in this paper, the maximum pixel loss within the field of view is only 3 pixels. This technology can effectively correct image drift caused by high temperatures during the in-situ progress, thereby helping material characterization.

The discourse of the anisotropic mechanical properties of a unit-built additively manufactured component depends on its microstructural features and inhomogeneous distribution. This work explores the microstructure distribution and deformation inhomogeneity during uniaxial tension of a laser melting deposited TA15 near-α titanium alloy via advanced in situ secondary electron microscopy and electron backscattered diffraction characterization. Microscopically, two major regions can be distinguished in the overall microstructure, including a Widmanstätten (αw) region along the prior β-grain boundary (GB) and a basketweave-α region within the columnar grains. These two different microstructural regions responded differently under the same tensile load conditions. In the early deformation stage, only conventional slip occurred in the basketweave-α region, whereas microscale shear bandings developed in both the basketweave-α and αw regions. As the deformation progressed, the strain was optimally accommodated by the basketweave-α region. Nevertheless, the largest strain accumulation occurred along the prior β-GB because of a high misorientation angle, which resulted in the formation of cracks. Subsequently, the growth and propagation of the cracks along the prior β-GB were relatively fast due to the weak obstruction caused by the low angle of misorientation in the αw region, resulting in early fracture of the sample.

The effect of heat treatment on the microstructure and high temperature mechanical properties of SLM GH4169 alloy was studied by using a self-developed in-situ high temperature tensile device. The results show that the grain morphology of as-built alloy changes from columnar crystal to equiaxed crystal after homogenization+solid solution+aging treatment （HSA）， coupling with Laves phase dissolution， and a large amount of γ′ and γ″ strengthening phase precipitates. At 650 ℃， the yield strength and tensile strength of the as-built sample are 574 MPa and 740 MPa， while the yield strength and tensile strength of HSA sample are 818 MPa and 892 MPa respectively， which are 42.5% and 20.1% higher than that of the deposited alloy. The deformation process can be further characterized by in-situ tensile testing. The surface grain undulation of the as-built sample gets larger， the coordinated deformation ability becomes stronger， and the plastic flow ability gets better.The cracks in the as-built sample are originated around the Laves phase， spreading along the dendrite towards the maximum shear stress， and shear fracture occurs after necking of the sample. In HSA samples， the cracks are initiated around carbides and propagating along the grain boundaries. The fracture mode is a mixed type， involving both intergranular and transgranular fractures.

This study presents a detailed investigation into the deformation behaviour and the factors affecting the strength and ductility of laser powder bed fusion (LPBF) Ni-based superalloy 718 (Inconel 718) in both as-printed and heat-treated conditions using in-situ SEM + EBSD. The results show that following post-deposition high homogenization temperatures, the columnar grain structure of the as-printed Inconel 718 alloy successfully transformed to a nearly uniform grain size and the subsequent aging processes facilitated the precipitation of strengthening phases (gamma ', ' , gamma"). The specimen subjected to heat treatment (HT1) exhibited higher strength but lower ductility, while the as-printed specimen shows higher tensile elongation due to high initial dislocation density. In contrast, the heat-treated (HT2) specimen presented a more optimal combination of strength and ductility. The underlying mechanism for the enhanced tensile properties in the HT2 specimen was nearly homogeneous deformation trend across the grains and ultrafine precipitation of hardening phases. In addition, the twin boundaries were stable in the early deformation stages and maintained their orientation. Multiple slip systems were activated at the high-deformation stage, resulting in a high proportion of geometric necessary dislocations. Further, the interaction of deformation-induced dislocation with twin boundaries transformed them into general boundaries such as high and low-angle grain boundaries, ultimately increasing ductility. On contrary, in the HT1 specimen, the deformation inhomogeneity in grains enabled the strain localization at grain boundaries, which ultimately caused the early formation of cracks.

Nickel-based GH3536 alloy exhibits high strength but low ductility when produced by selective laser melting (SLM), which hinders its widespread application in aerospace. This paper employed a 'two-step ' method of heat treatment to optimize the microstructure of the SLM GH3536 alloy and investigated the mechanical properties. Tensile tests were conducted on SLM GH3536 alloy before and after heat treatment at 750 degrees C, using an in -situ high-temperature tensile stage. The relationship between the microstructural evolution and deformation behavior of the alloys was investigated by combining the in -situ tensile experiments and crystal plasticity finite element method (CPFEM). The results suggested that the elongation can be increased by 80% without a significant reduction in tensile strength. The improved elongation is attributed to the complete recrystallization, formation of annealed twins and serrated grain boundaries after heat treatment. The study also investigated the deformation behavior and fracture mode of the alloy before and after heat treatment. Discussion was done on the influence of the microstructure, particularly the twin and serrated grain boundaries on the alloy ' s plastic deformation. This study enhanced the understanding of plastic deformation of SLM GH3536 alloy and provided a valuable reference for the design and post-treatment of superalloy.

The effect of the grain boundary (GB) misorientation on plastic deformation of Inconel 718 (IN718) alloy was investigated in this paper, using in-situ tensile experiment at 650 °C in combination with crystal plasticity finite element method (CPFEM). The results indicate that dislocations tend to accumulate at GBs to form stress concentration, but the degree of stress concentration does not necessarily increase with the increase of the GB misorientation. It is attributed to the slip transfer at the GBs, determined by the angle between the slip systems of the two adjacent grains. There is a significant uncertainty in the slip transfer for GB misorientation larger than 10°. However, the m_αβ^'( SF_α + SF_β) criterion, which is a function of the Luster and Morris m_αβ^' combining the Schmid factors of the two slip systems with the GB misorientation, has some statistical separation significance. Slip transfer tends to appear at GB misorientation less than 30° and m_αβ^'( SF_α + SF_β) > 0.78 . This study clarifies the mechanism of the influence of GB misorientation on IN718 microplastic deformation and provides a new strategy to study the deformation behavior of superalloys.

Lithium (Li) metal is a promising candidate for next-generation anode materials with high energy densities. However, Li dissolution/deposition processes are limited at the upper surface in contact with the electrolyte, which brings a locally high current density and then results in dendritic Li growth. This restraint of the local surface reaction during cycling has not been solved by commonly used modification strategies. In this study, a three-dimensional (3D) Li+ conductive skeleton is activated from atomic layer deposition (ALD) coating Li3PO4 (LPO) on the surface of the Ni foam (LPNF). Then, the skeleton is efficiently constructed in the Li metal anode by the lower-temperature Li infusion. Ionic conductor LPO layers and electronic conductor Ni fibers supply charge transport channels between the electrolyte and the internal Li. The mixed conductive network realizes holistic charge transfer, which is proved by in situ scanning electron microscopy experiments. In virtue of dispersive dissolution/deposition and optimized electrochemical kinetics brought by a Li+ conductive network, the composited Li electrode presents an excellent symmetric battery cycling stability (over 1200 h) and enhanced rate performances (stable cycling even at 10.0 mA cm-2). When matching with a LiCoO2 (LCO) cathode, LCO||Li@LPNF full batteries exhibit a capacity retention of 80.8% over 250 cycles. During cycling, there was no evidence of dendrite growth and the remaining Li in the composited anode showed a smooth, compact, and well-combined condition with LPNF. Through constructing a 3D Li+ conductive network, the composited Li metal anode breaks through the limit of the local surface reaction; this work proposes a novel insight of realizing holistic charging/discharging for the dendrite-free Li metal anode.

In this paper, the deformation behavior of a nickel-based single-crystal superalloy with [ 1 40] and [ 3 40] orientations was studied at room temperature by in situ electron backscattered diffraction (EBSD) tensile equipment. The mechanical properties, slip behavior and the corresponding Schmidt factor were analyzed. The deformation bands generated during the plastic deformation stage were found and characterized by using the electron backscattered diffraction (EBSD) technique. Furthermore, the formation and propagation of deformation bands played a softening effect on stress–strain curves; however, the secondary slip bands occurring after the propagation of deformation bands played a hardening effect. Finally, the formation of deformation band and its propagation on the mechanical properties are discussed.

The control of δ precipitations is important during the thermal processing of Inconel 718 superalloy (IN718) because it can control the grain size and affect the mechanical properties of the material. The main purpose of this study was the effects of plastic deformation and Grain Boundary Misorientation (GBMO) on δ phase precipitation at grain boundaries (GBs). The content of the δ phase and the number of precipitated orientations at the GB were statistically analyzed. It was found that the δ phase grew into grains along the {111} plane of γ-matrix after nucleation at the GB. Plastic deformation can change the morphology and precipitate location of δ phase, with the increasing of plastic strain, the content of the δ phase and the number of precipitated orientations in GBs increased, which was related to the piling up of dislocations caused by deformation and the slip of {111} plane. For the undeformed samples, the δ phase precipitation at the GB was affected by the GBMO, which was consistent with the change of GBs energy with the GBMO. The influence of the structure and characteristics of the interfaces (GBs and twin boundaries) on the precipitation behavior of the δ phase is also analyzed in this study.

The delta (δ) processing strategy is an efficient heat treatment to refine and homogenize the grain microstructure of Inconel 718 superalloy (IN718). However, the microstructure becomes complicated by the effect of pre-precipitated δ phases, due to the coupling of precipitations, high temperature, and loading stress. The present study aims to clarify the effect of δ phases on the microstructure evolution of IN718, especially the promoting effect on deformation twins (DTs) and dynamic recrystallization (DRX) behavior. The results show that the promoting effect of δ phases on the formation of DTs was attributed to the lower stacking fault energy (SFE) caused by the precipitation of δ phases and the local stress concentration caused by the distribution of δ phases. The area fraction of DRX grains in the compressed δ-containing specimen was 21% higher than that in the compressed δ-free specimen, which was associated with the discontinuous dynamic recrystallization (DDRX) nucleation stimulated by the single δ phase and the continuous dynamic recrystallization (CDRX) nucleation promoted by the distribution of δ phases. Furthermore, a novel heteroepitaxial recrystallization (HERX) mechanism was found based on inverse precipitation from the undissolved δ phase to γ matrix phase grains with a crystallographic orientation relationship of (0_10)[1 0 2]δ//(__111)[0 1 1]HERX.