Random Grain Research Articles

Mechanical characterizations of η′-Cu6(Sn, In)5 intermetallic compound solder joint: Getting prepared for future nanobumps

As advanced silicon manufacturing processes slow down in scaling, three-dimensional stacking of chips has become a future trend in microelectronic industry. High-density bonding technology is one of the core technologies used to achieve the stacking. In this work, we explored a new bonding technology that is possible to manufacture future high-density interconnects. We fabricated a series of sandwich structure solder joints with different thicknesses using SnBiIn-based nanoparticles under a low bonding temperature of 100 °C. The intermetallic compound (IMC) at the interface is proven to be η′-Cu6(Sn, In)5 nanocrystals with random grain orientations through X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and atomic probe tomography (APT). The hardness and elastic modulus of η′-Cu6(Sn, In)5 were measured to be 4.093 GPa and 79.586 GPa by micropillar compression tests, respectively, decreasing by 35% and 29.1% compared to Cu6Sn5. Therefore, doping In atoms reduces the brittleness of IMCs, providing a new approach for mitigating the mechanical failures of full IMC bump. First-principles calculation also verified the change in mechanical properties. Furthermore, a full-Cux(Sn, In)y IMCs solder joint and an array of 3 μm solder joints were fabricated experimentally using the bonding technology. This technology successfully demonstrates a pioneer interconnection bonding methodology for future ultra-high-density chip stacking using low melting point solder nanoparticles.

In-situ analysis of SCC initiation on Alloy 600 surface in primary water environment using digital image correlation with electron backscatter diffraction

This study examined the stress corrosion cracking (SCC) phenomenon of Alloy 600 in a high-temperature primary water environment. The investigation involved the observation of local plastic deformation and SCC initiation on the specimen surface using an observation apparatus, comprising a laser confocal microscope (LCM) and an autoclave equipped with a diamond window view-port. Prior to conducting the SCC initiation test, the crystalline structure of the specimen, including grain boundary (GB) characteristics, Schmid factor, and trace inclination angle, underwent examination using an electron backscatter diffraction (EBSD) technique. The local strain distribution was subsequently analyzed using a digital image correlation (DIC) method, employing LCM images obtained during the SCC experiments. The ex-situ EBSD analysis indicated that SCC mainly initiated at random high-angle grain boundaries (HAGB) with trace inclination angles close to 90° relative to the tensile axis. DIC analysis further revealed that most GBs in the vicinity of the highly strained area cracked among random HAGBs with a high trace inclination angle to the tensile axis. This confirms that the local strain gradient at GBs plays an important role in SCC initiation, serving as a more suitable indicator of an additional stress component to effective normal stress acting on GBs compared to the Schmid factor mismatch.

Interplay between high-temperature creep deformation behavior and nanoscale precipitate evolution in a newly designed Fe–Ni-based superalloy

In an endeavor to achieve the critical goals of carbon neutrality, an explorative study was conducted to scrutinize the precipitate evolution and high-temperature creep behavior of an innovative and cost-effective Fe–Ni-based superalloy that was meticulously engineered for the next-generation ultra-supercritical (USC) power plants. The creep experiments conducted at temperatures and stresses of 650 °C/280 MPa (17,179 h), 675 °C/250 MPa (10,271 h), and 700 °C/250 MPa (2378 h), coupled with proficient data fitting were employed to accurately assess the long-term service performance of the superalloy under real-world operational environments. Though it can withstand theoretically an intense stress of 130 MPa at 700 °C for approximately 30 years as calculated by the Larson-Miller equation, its performance was not without a degree of perceived vulnerability. This was primarily traced to the conspicuous coarsening behavior of the precipitate-free zones (PFZs)/discontinuous coarsening zones (DCZs) formed in the grain boundaries (GBs) on a longer time scale. It had a significant diminishing impact on the overall strength of the GBs, resulting in a recorded creep life that was considerably shorter than initially projected. Moreover, a synergistic mechanism between PFZs/DCZs with TiC carbides was advanced to interpret the intergranular fracturing dynamic, which was postulated due to the evidence gathered from electron backscatter diffraction (EBSD), highlighting that the banded distribution of TiC carbides circumambient to GBs engendered considerable stress aggregation. Conversely, the plentiful supply of coincidence site lattice (CSL) boundaries disrupted the continuous network structure of random high-angle grain boundaries (HAGBs), thereby creating an effective barricade against the proliferation of cracks. These empirical findings paved the way for the proposition of an enhanced blueprint and the industrial utilization of such.

Investigation into hydrogen assisted fracture in Nickel oligocrystals

This study investigates the hydrogen embrittlement (HE) behavior of Nickel-201 alloy using the oligocrystal approach. To comprehend the influence of microstructure toward HE, various types of tensile oligocrystals (True-oligocrystals, Quasi-oligocrystals, Identical-oligocrystals, and Bi-crystal type oligocrystals) with diverse microstructure (in terms of Schmid factor distribution and grain boundary types) are generated using a combination of heat treatment and slicing method. The electron backscatter diffraction (EBSD) analysis is used to validate the development of the desired tensile oligocrystal samples. Identical oligocrystal samples established the transition in fracture mode from ductile transgranular (TG) to brittle intergranular (IG), solely driven by hydrogen uptake. Post-tensile deformation analysis validated the hydrogen-induced IG fracture initiation and propagation along the random high-angle grain boundaries (RHAGBs) only. Bi-crystal type oligocrystals with low angle grain boundaries (LAGBs) and coincident-site lattice (CSL) Σ3 grain boundaries exhibited resistance to hydrogen-induced intergranular fracture, thus establishing the ‘special’ nature of these grain boundaries against the HE under current testing conditions.

Effects of KoBo-Processing and Subsequent Annealing Treatment on Grain Boundary Network and Texture Development in Laser Powder Bed Fusion (LPBF) AlSi10Mg Alloy

It is well known that the properties of polycrystalline metals are related to grain boundaries (GBs), which are fundamental structural elements where crystallographic orientations change abruptly and often exhibit some degree of symmetry. Grain boundaries often exhibit unique structural, chemical, and electronic properties that differ from bulk crystalline domains. Their effects on material properties, including mechanical strength, corrosion resistance, and electrical conductivity, make grain boundaries a focus of intense scientific investigation. In this study, the microstructural transformation of an AlSi10Mg alloy subjected to KoBo extrusion and subsequent annealing is investigated. A notable discovery is the effectiveness of a strain-annealing method for grain boundary engineering (GBE) of the LPBF AlSi10Mg alloy. In particular, this study shows a significant increase in the population of coincidence site lattice boundaries (CSL), which embody the symmetry of the crystal lattice structure. These boundaries, which are characterised by a high degree of symmetry, contribute to their special properties compared to random grain boundaries. The experimental results emphasise the crucial role of strain-induced boundary migration (SIBM) in the development of a brass texture in the microstructure of the alloy after annealing. In addition, the presented results demonstrate the feasibility of applying GBE to materials with high stacking fault energy (SFE), which opens up new possibilities for optimizing their properties.

Anisotropy of Anion Diffusion in All-Inorganic Perovskite Single Crystals.

Ion diffusion is a fundamentally important process in understanding and manipulating the optoelectronic properties of semiconductors. Most current studies on ionic diffusion have been focusing on perovskite polycrystalline thin films and nanocrystals. However, the random orientation and grain boundaries can heavily interfere with the kinetics of ion diffusion, where the experimental results only reveal the average ion exchange kinetics and the actual ion diffusion mechanisms perpendicular to the direction of individual crystal facets remain unclear. Here, the anion (Cl, I) diffusion anisotropy on (111) and (100) facets of CsPbBr3 single crystals is demonstrated. The as-grown single crystals with (111) and (100) facets exhibit anisotropic growth with different halide incorporation, which lead to different resulting optoelectronic properties. Combined experimental characterizations and theoretical calculations reveal that the (111) CsPbBr3 shows a faster anion diffusion behavior compared with that of the (100) CsPbBr3, with a lower diffusion energy barrier, a larger built-in electric field, and lower inverse defect formation energy. The work highlights the anion diffusion anisotropic mechanisms perpendicular to the direction of individual crystal facets for optimizing and designing perovskite optoelectronic devices.

Large-area polycrystalline α-MoO3 thin films for IR photonics

In recent years, the excitation of surface phonon polaritons (SPhPs) in van der Waals materials received wide attention from the nanophotonics community. Alpha-phase Molybdenum trioxide (α-MoO3), a naturally occurring biaxial hyperbolic crystal, emerged as a promising polaritonic material due to its ability to support SPhPs for three orthogonal directions at different wavelength bands (range 10–20 μm). Here, we report on the fabrication, structural, morphological, and optical IR characterization of large-area (over 1 cm2 size) α-MoO3 polycrystalline film deposited on fused silica substrates by pulsed laser deposition. Due to the random grain distribution, the thin film does not display any optical anisotropy at normal incidence. However, the proposed fabrication method allows us to achieve a single α-phase, preserving the typical strong dispersion related to the phononic response of α-MoO3 flakes. Remarkable spectral properties of interest for IR photonics applications are reported. For instance, a polarization-tunable reflection peak at 1006 cm−1 with a dynamic range of ΔR = 0.3 and a resonance Q-factor as high as 53 is observed at 45° angle of incidence. Additionally, we report the fulfillment of an impedance matching condition with the SiO2 substrate leading to a polarization-independent almost perfect absorption condition (R < 0.01) at 972 cm−1 which is maintained for a broad angle of incidence. In this framework our findings appear extremely promising for the further development of mid-IR lithography-free, scalable films, for efficient and large-scale sensors, filters, thermal emitters, and label-free biochemical sensing devices operating in the free space, using far-field detection setups.

Research on Flexible Transparent Conductive Electrodes Based on Ultra-Thin Ag in the Form of Grain Boundary with IZO Layer

In this paper, we investigated a transparent conductive electrode (TCE) that satisfies electrical, optical, and mechanical properties, formed by depositing ultra-thin Ag metal in the form of a random grain boundary with an indium zinc oxide (IZO) layer on a PET substrate. Commonly used ITO electrodes are brittle and difficult to apply to flexible devices. In contrast, IZO-based electrodes are mechanically flexible and can be used as flexible TCE, and have high electrical and optical properties. A 90 nm thick IZO electrode has a transmittance of 90.2% at a wavelength of 460 nm and a sheet resistance of 29.5 ohm/sq. In particular, Ag metal was deposited in the form of an atypical metal island using an RF magnetron sputtering system. At 3 nm there were few metal clusters in the form of islands, and many void channels were formed, resulting in high sheet resistance as well as a decrease in optical transmittance. However, about 5 nm thickness, the number of void channels decreased and the optical path changed, improving the electrical and optical properties. Results showed that the sheet resistance was reduced to 19.8 ohm/sq, and the transmittance was also increased to 91.1%. The mechanical properties were also found to be the same for conventional IZO and Ag/IZO TCE.

Microstructure evolution and strengthening mechanism of CoCrFeMnNi HEA/Zr-3 brazed joints reinforced by fine-grained BCC HEA and HCP Zr

In the pursuit of manufacturing intricate components for the nuclear industry, we developed a novel Zr63.2Cu36.8 (wt.%) alloy via vacuum melting for brazing applications involving equiatomic high-entropy alloys (HEA) of CoCrFeMnNi and zircaloy (Zr-3). We systematically investigated the influence of various brazing parameters on microstructure evolution and shear properties. Furthermore, we established a comprehensive understanding of the relationship between the lattice structure of interfacial products, residual stress, and fracture behavior in HEA/Zr-Cu/Zr-3 joints. Our findings revealed that under specific conditions (1010 °C for 10 min), the reaction products in HEA/Zr-Cu/Zr-3 joints consisted of lamellar HEAP/lamellar Zr(Cr,Mn)2, granular (Zr,Cu)/Zr2(Cu,Ni,Co,Fe), bulk Zr(Cr,Mn)2, and Zrss. With increasing temperature and prolonged holding time, the layered HEAP and Zr(Cr,Mn)2 phases adjacent to the HEA substrates thickened, while the relative amounts of Zr2(Cu,Ni,Co,Fe) decreased, with a remarkable increase in ductile Zrss. Growth kinetics analysis of the reaction layer and EBSD analysis indicated that the HEAP phases exhibited a lower growth rate compared to the Zr(Cr,Mn)2 layer during brazing, and both phases exhibited random grain orientations. Particularly noteworthy was the precipitation of (Zr,Cu) within the layered Zr(Cr,Mn)2, which increased and coarsened with higher temperatures and extended durations. Finite element analysis and TEM analysis revealed higher residual stresses at the non-coherent Zr(Cr,Mn)2/HEAP interface with a lattice mismatch of 40.6%. The body-centered cubic (BCC) structural HEAP, composed of fine grains, effectively mitigated the concentrated residual stresses due to its superior plasticity. Moreover, micro-nanoscale close-packed hexagonal (HCP) precipitates (Zr,Cu) were distributed within the brittle Zr(Cr,Mn)2 phases, contributing to the overall strength improvement of the joints. Consequently, high-quality HEA/Zr-3 joints were achieved, featuring a maximum strength of 172.1 MPa, equivalent to approximately 62.6% of the yield strength of Zr-3. These results highlight the potential of Zr63.2Cu36.8 (wt.%) alloys in advanced brazing applications.

Effect of grain boundary engineering on corrosion behavior of 316 L stainless steel bipolar plate in proton exchange membrane fuel cells environment

This study illustrates the effect of grain boundary engineering (GBE) on the corrosion behavior of 316 L stainless steel (SS) in a proton exchange membrane fuel cells (PEMFCs) environment. It shows that the GBE increased the density of grain boundary and the coincidence site lattice (CSL) performes a better corrosion resistance, a preferential corrosion phase that the impurity elements are more likely biased at during the cast, the Random grain boundaries(RGBs) decreases. Furthermore, the texture on GBE2's closed-packed (111) plane reduces the surface atoms' dissolution velocity, thereby, decreasing the thermodynamic tendency to form dense corrosion films and nucleation kinetics. The above combined reasons lead to the lowest corrosion resistance of GBE2.

Effect of arc rotation on the enhancement of mechanical properties of ER70S6 in WAAM

Inceptive studies were done on using Rotational/Spin arc technique for Wire Arc Additive Manufacturing (WAAM). A wall of low alloy steel was build and the effect of rotating the arc on the mechanical properties and the microstructural properties were studied. Tensile testing conducted across multiple directions shows an average tensile strength of 550 MPa which is comparatively higher by approximately 90 MPa than other stationary arc techniques used to fabricate the same material, however with lesser percentage elongation. Microhardness testing revealed that the average hardness of the build to be 156 HV0.5. Microstructural studies revealed reduction in grain sizes and random grain orientation; with the misorientation and rotation angle plots exhibiting the presence of High Angle Grain Boundaries (HAGB's), which could be attributed as the primary factors for the improvement in the tensile properties.

Study on defects, densification, and microstructural evolution of additively manufactured Al-Zn-Mg-Cu-Hf alloy

The present work proposes a new alloy composition design, with 1.5–3.0 wt% Hf added into a conventional high-performance Al-Zn-Mg-Cu alloy, aiming to address the notorious high crack sensitivity faced by metal additive manufacturing (AM). The effects of processing parameters or Hf content on the defects (pores, cracks, and distortions), the densification behavior, and the microstructural characteristics of grains have been investigated. It is demonstrated that by optimizing the laser processing parameters (power and scanning speed), a laser powder bed fused (LPBF) Al-Zn-Mg-Cu-Hf alloy with a high relative density (> 99.9 %) and without unwanted lack-of-fusion pores, keyhole-induced pores, cracks, and distortions is obtainable. In addition, the study reveals that Hf significantly affects the grain morphology, size, and orientation through the formation of primary L12-Al3Hf phase, because L12-Al3Hf can act as ideal heterogeneous nucleation sites for α-Al. With increased Hf addition, more equiaxed grains replace initial columnar grains, accompanied by a reduction of mean grain size and a more random grain orientation. Particularly, at the maximum Hf addition of 3.0 wt%, a fully equiaxed grain structure is accomplished and the texturing is minimized.

High strength, ductility and sheet formability by normalizing and quenching of low carbon microalloyed dual-phase steel

This work investigates the possibility of developing high strength, ductility, and normal-anisotropy in cold rolled (CR, ∼84%) 0.05 wt% carbon microalloyed dual-phase (DP) steel sheets by normalizing (N, 920°C, 30 min) followed by intercritical annealing and quenching (IA&Q, 80 0°C, 3 min). CR + N produces ferrite with ∼6.9μm grain size and ∼0.23 bainite fraction with ∼5.3μm packet size. A high engg. (true) strength of ∼605(∼798)MPa; uniform engg. (true) strain eU≈0.32 (εU≈0.28); engg. fracture strain, ef≈0.48; with high normal average anisotropy (r‾) of ∼1.84 and low planar anisotropy, Δr of ∼0.30 could be obtained. Further, IA&Q produced ferrite with ∼6.3μm average grain size, ∼0.25 martensite fraction (Ceq≈0.16) with ∼3.2μm island size. A high engg. (true) strength of 690(864)MPa; engg. (true) uniform strain of ∼0.25 (∼0.22); engg. fracture strain ∼0.39; and high r‾ of ∼1.51, low Δr of ∼0.31, suitable for sheet metal formability, were obtained. The high strength could be attributed to (a) fine ferrite grain size, (b) secondary phase fraction (∼0.23B/∼0.25M), packet size and island morphology, and (c) geometrically necessary boundaries (GNB). High ductility could be due to (a) fine ferrite grains with secondary phase morphology, (b) GNB, coincident site lattice boundaries (CSLB), and random high angle grain boundary (RHAGB) networking. Better anisotropic properties could be associated with strong γ-fiber, and suppression of α-fiber and θ-fiber texture. Loci in the stress and strain space indicate that the hydraulic bulge and plane-strain biaxial strength-ductility improves to 950MPa-0.41 and 1030MPa-0.67 after CR + N, and to 968MPa-0.30 and 1070MPa-0.58 after CR + N + IA&Q.

Grain boundary network evolution in electron-beam powder bed fusion nickel-based superalloy Inconel 738

Additive manufacturing (AM) of alloys has attracted much attention in recent years for making geometrically complex engineering parts owing to its unique benefits, such as high flexibility and low waste. The in-service performance of AM parts is dependent on the microstructures and grain boundary networks formed during AM, which are often significantly different from their wrought counterparts. Characteristics such as grain size and morphology, texture, and the detailed grain boundary network are known to control various mechanical and corrosion properties. Advanced understanding on how AM parameters affect the formation of these microstructural characteristics is hence critical for optimising processing parameters to unlock superior properties. In this study, the difficult-to-weld nickel-based superalloy Inconel 738 was fabricated via electron-beam powder bed fusion (EPBF) following linear and random scanning strategies. Random scanning resulted in finer, less elongated, and crystallographically more random grains compared to the linear strategy. However, both scanning strategies achieve unique high grain structure stability up to 1250 ℃ due to the presence of carbides pinning the grain boundaries. Despite significant difference in texture and morphology, majority of grains terminated on {100} habit planes in both linear and random built samples. The results show potential for controlling grain boundary networks during EPBF by tuning scan strategies.

Generation and origin of persistent high excess pore water pressure in debris flows

Due to building up excess water pressure, debris flows differ markedly from other water-sediment mixtures in mountain basins. Although a number of mechanisms are known to create excess water pressure, persistent high excess water pressure develops in static-quasistatic debris-flow slurries when possible triggers such as saturation, contraction, and Reynolds stress are absent. This suggests that there exist more fundamental mechanisms for the creation and persistence of high excess water pressure. Using 12 clastic materials with four maximum diameters up to 40 mm from three typical debris flows in Southwest China, we make comparative measurements of excess water pressure, gravity drainage, and decanting of water on 12 pairs of debris-water mixtures. It is found that saturation is not a mechanism for excess water pressure generation, which can be ascribed to the heterogeneity of saturated sediments. Mixing undoubtedly creates persistent high excess water pressure in the mixed saturated sediments. Thorough mixing causes the homogenization of water-saturated sediments through random grain rearrangements. The particles in the homogeneous debris-water mixtures stay suspended in water, resulting in excess water pressure derived from particle weight. More significant is the integration of clasts and water over the timescales for debris-flow durations promoted by mixing, which leads to the persistence of high excess water pressure. The development of persistent high excess water pressure in sediment-water mixtures is controlled by external factor—mixing, and internal factors, including sorting of sediments and water content of mixtures.

Enhancement of the resistance to hydrogen embrittlement by tailoring grain boundary characteristics in a low carbon high strength steel

In this work, the feasibility of using “grain boundary engineering” to reduce the susceptibility to hydrogen embrittlement in a low carbon low alloy steel was examined. By adding Cu element, the fraction of random grain boundary (RGB) exhibited the highest value in the steel with 1%Cu, while the fraction of special grain boundary (SGB) showed a monotonical decline. The slow strain rate tensile (SSRT) test revealed that the elongation loss presented an increase with Cu addition increasing from 1 % to 3 %. This can be explained in terms of hydrogen diffusion, hydrogen trap and crack propagation. The steel with 1%Cu had a higher fraction of high angle grain boundary (HAGB), which contributed to a higher density of hydrogen traps and a lower hydrogen diffusion rate. Moreover, the steel with 1%Cu had the highest fraction of SGB (∑3, ∑5, ∑7 and ∑≥9), which was beneficial to the resistance to crack propagation. Under the combined effect of RGB and SGB, a higher resistance to hydrogen embrittlement was achieved in the steel with 1%Cu.

Effect of grain orientation and precipitates on the superelasticity of Fe–Ni–Co–Al polycrystalline alloys

In this paper, the evolution of microstructure in Fe–Ni–Co–Al polycrystalline alloys and its effects on mechanical properties were systematically investigated. The results show that the proportion of high-angle grain boundaries (HAGBs) is 98.1 % with 51.2 % of Σ3 GBs during the solid solution (SS) process. The distribution of Σ3 GBs and other HAGBs (non-Σ3 HAGBs) are relatively dispersed, which prevents the formation of a specific orientation. In addition, there is no discernible anisotropy in GB migration during the SS process, ultimately resulting in the absence of texture. In contrast, during the directional recrystallization (DR) process, the directional migration of GBs is driven by the temperature gradient. Random high-angle grain boundaries (RHAGBs) with Σ values exceeding 29 possess higher GB energy and migration rate compared to low-angle grain boundaries (LAGBs) and HAGBs, making them more susceptible to GB migration. In the grain incubation area, the proportion of RHAGBs between grains oriented {111}<214> (grain 2 and grain 5) and their surrounding grains are 90 % and 75 %. These grains have the growth advantage and eventually form the main orientation {111}<214>. While the proportion of RHAGBs between grains oriented {114}<214> (grain 11) and its surrounding grains is only 65 %, characterized by lower GB energy and migration rate. Therefore, these grains eventually form the minor orientation {114}<214>. The coherent L12-Ni3Al (γ′) precipitates were observed in both the SS-AG (SS after aging) and DR-AG (DR after aging) treatments. The DR-AG alloy, characterized by {111}<214> and {114}<214> orientations and γ′ precipitates, exhibited a 3.6 % recoverable strain and a 1.2 % superelastic strain, whereas no evident superelastic behavior was found in the SS-AG alloy, which featured a random texture and γ′ precipitates.

Effects of grain boundary characters on the carbide precipitation in Inconel Alloy 600

ABSTRACT The precipitation of carbide at the grain boundary is one of the key factors that influences the resistance of intergranular corrosion. The morphology and growth mechanism of the carbides precipitated at different grain boundaries in Alloy 600 aged at 715°C for different times were investigated by transmission electron microscopy. Two types of carbides, M23C6 and M7C3, can be observed in the sample. The grain boundary character significantly affects the precipitation and distribution of different carbides. The face-centred cubic structured fine M23C6 has a semi-coherent orientation relationship with the matrix, and mainly precipitates at Σ3 grain boundary in all the samples, and at Σ9 grain boundary in the short-term aged samples. The large M7C3 has a hexagonal crystal structure, which does not have typical orientation relationship with the matrix, and precipitates at Σ9 grain boundary in the long-term aged samples, and at Σ27 grain boundary and random grain boundary in all the samples.

The effect of solutionizing heat treatment on ductility loss and damage evolution in AA7075 aluminum sheet deformed at 450°C

The high-temperature deformation behavior of AA7075 sheet was investigated using hot tensile testing. The specimens were solutionized at 475 °C for 15 min prior to cooling to a deformation temperature between 300 and 450 °C. AA7075 exhibited a progressive rise in ductility with increasing deformation temperature until a sudden drop in ductility was observed at 450 °C. The loss of ductility is attributed to localized melting at the grain boundaries during the solutionizing step. Increasing the holding time at 450 °C prior to the onset of deformation resulted in the gradual restoration of the ductility of the material as a result of isothermal solidification. Samples which are directly heated to 450 °C, without solutionizing at 475 °C, did not experience any loss of ductility. The elongation of non-solutionized sample was always greater than that of the solutionized one when deformation is carried out at 450 °C. This is attributed to the different distribution of particles on the grain-boundaries within the two materials. Trace analysis revealed that intergranular crack propagation proceeds preferentially on higher-indexed random grain boundary planes such as (533), (420), and (531).

The influence of CeO2 particle with various sizes on the microstructure and properties of electrodeposited Ni-CeO2 composite coatings

In current work, Ni-CeO2 composite coatings with various CeO2 particle sizes are prepared in Watts bath. The influence of CeO2 particle with various sizes on the microstructure and properties in electrodeposited Ni-CeO2 composite coatings is investigated. When compared to microparticles, nanoparticles exhibit greater benefits in optimizing the surface topography and achieving a more homogeneous coating surface. Furthermore, the nano coatings possess a more random surface grain orientation, a high level of grain refinement, and numerous low angle grain boundaries (LAGB). The analysis of macro and micro textures in coatings unveils that nanoparticles exhibit superior performance in suppressing texture compared to microparticles. Microparticles primarily contribute to the improvement of microhardness in the nickel coating, whereas nanoparticles play a crucial role in ensuring a homogeneous distribution of microhardness. The electrochemical test results indicate that the corrosion resistance of nano coatings surpass micro coatings due to the grain refinement and homogeneous corrosion. Nanoparticles demonstrate a higher efficiency in promoting the formation of NiO and Ni(OH)2 within the coatings compared to microparticles. As a result, the corrosion resistance of the nano coatings is significantly enhanced.