Microstructural Defects Research Articles

3D hierarchical porous structures printed from a silica-nickel composite paste

Material extrusion of paste as one of the 3D printing techniques is commonly used in additive manufacturing industry. It allows to efficiently obtain structures of complex geometry at a relatively low cost. Ceramics are among the materials eagerly printed with this technique, especially as a support material. Hence, the combination of silica as base material and nickel as catalyst seems to be a highly promising system in processes such as CO2 methanation or hydrogenation processes.The key aspects that should be taken into consideration when designing a new material are the proper material composition, its microstructure, as well as the final properties. From the point of view of the above-mentioned applications, material should have high open porosity. Appropriate micro- and macroporosity enable the optimal flow of liquid and gaseous reagents through the material, ensuring high efficiency of the processes carried out. It is also crucial to select the appropriate catalytic material, hence the use of nickel as a catalytically active metal was proposed for the research.This article demonstrates the development, preparation and characterization of silica-nickel porous structures obtained via material extrusion. The nanosilica-Ni paste with 75 wt% of Ni powder particles was prepared with stirring and degassing for homogenous consistency. 3D printed scaffolds have undergone heat treatment to remove the organic binders and partially sintered to achieve a relevant mechanical strength. The analysis of the paste was performed using the detailed thermal analysis, XRD analysis and Raman spectroscopy for a determination of the optimal thermal processing conditions. In addition, the characterization of the final materials was carried out to confirm the effectiveness of the procedures developed. Application of the reductive atmosphere (mixture of N2+H2) during heat treatment prevented nickel particles from oxidation, as well as strongly eliminated the microstructure defects such as cracking and material shrinkage. The results demonstrate the perspective application of material extrusion as a printing technique of highly porous materials with well-preserved pre-designed 3D geometry.

Half-Heusler alloys as emerging high power density thermoelectric cooling materials

To achieve optimal thermoelectric performance, it is crucial to manipulate the scattering processes within materials to decouple the transport of phonons and electrons. In half-Heusler (hH) compounds, selective defect reduction can significantly improve performance due to the weak electron-acoustic phonon interaction. This study utilized Sb-pressure controlled annealing process to modulate the microstructure and point defects of Nb0.55Ta0.40Ti0.05FeSb compound, resulting in a 100% increase in carrier mobility and a maximum power factor of 78 µW cm−1 K−2, approaching the theoretical prediction for NbFeSb single crystal. This approach yielded the highest average zT of ~0.86 among hH in the temperature range of 300-873 K. The use of this material led to a 210% enhancement in cooling power density compared to Bi2Te3-based devices and a conversion efficiency of 12%. These results demonstrate a promising strategy for optimizing hH materials for near-room-temperature thermoelectric applications.

Influence of heat treatment, microstructure evolution, and damage mechanism on high cycle fatigue behaviour of additively manufactured Ti-modified Al 2024 alloy

The high cycle fatigue behaviour of titanium modified Al 2024 alloy produced by laser powder bed fusion (LPBF) is investigated to elucidate the effect of the microstructural features, residual stress, and defects (such as porosity and lack of fusion) on dynamic behaviour. The titanium acts as a grain refining agent; it can reduce the solidification cracking and produce the ultrafine-grained (UFG) microstructure in aluminium alloys. The 2% titanium addition resulted in the UFG microstructure with an average size of 0.52 μm in as-built samples. The microstructural features were examined through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron back-scattered diffraction (EBSD) analysis. The influence of the microstructural features, such as grain size, dislocation density, precipitate-dislocation interaction, etc., on the fatigue life of as built and T6 heat treated samples was analysed in detail. The effect of varying stress amplitude at a stress ratio of 0.1 and a frequency of 30 Hz was investigated for the as-built and heat-treated sample. The T6 heat-treated sample showed 21.9% higher fatigue strength compared to the as-built samples (87.8 MPa in the heat-treated sample compared to 72 MPa in the as-built sample). The corresponding damage mechanisms are thoroughly explored through scanning electron fractography, TEM, and EBSD. The defects like porosity and lack of fusion defects in the surface or sub-surface level were observed to be critical regions as crack initiation sites.

An Investigation into the Deterioration of Copper Surface Quality in Plasma Electrolytic Polishing

Plasma electrolytic polishing (PEP) is widely used in the finishing process of metallic parts. Some parts with narrow structures always suffer from surface quality deterioration in the PEP process. In this paper, the deterioration of surface quality was studied to reveal the vapor film evolution mechanism during the polishing. The conditions for the bump defects generation were investigated with the comparison of polished surface morphology under different voltages and immersion depths. The reasons for the bump defects generation were analyzed through the compositions, the chemical states of the elements, and the microstructure of bump defects. The relationship between the current density, the thickness of the vapor film, and the heat to maintain the vapor film was discussed. The vapor film was maintained by Joule heat generated by itself. During the PEP process, excessive current density on the anode surface made the vapor film thickness greater than the critical value of heat could maintain, leading to the collapse of the vapor film. The anode then came into partial contact with the electrolyte, resulting in bump defects. As a result, it is suggested that the thickness of the vapor film be reduced to prevent the surface quality of narrow structures from deteriorating.

Effect of Cobalt Fraction Mixing WC Clads on Microstructural Evolution, Crack Formation and Tribological Properties by Laser Cladding

In the present work, a ceramic-matrix composite coatings with different weight percentages of Co additive in the WC powders was studied on 45 steel by laser cladding. The effect of cobalt mixture with WC on mechanical properties such as microstructural evolution, hardness, wear and residual stress behavior of the coatings was carried out. The results show that high residual stresses induce significant cracking on 100% WC and that cracking activity is reduced by adding concentrations of 20% Cobalt to WC. Further, the microhardness of the coatings was more than five times higher than that of the substrate. The observation of the microstructural evolution reveals the fracture mechanism is a typical intergranular fracture in the molten zone and the crack propagates through the interior of the unmelted WC at 100% WC. Overall, the additive of high cobalt in WC did not result in a reduction of residual stresses due to less amount of brittle carbide. However, a reduced number of microstructural defects as well as a better wear behavior were obtained for the WC coated layers with suitably added Cobalt alloys.

Nano to micrometer range particle size effect on the electrical and piezoelectric energy harvesting performances of hydroxide mediated crosslinked PVDF composites

The polar phase and piezoelectric response of filler-loaded PVDF-based composites very often depend on the interfacial interaction between the filler surface and PVDF dipoles. In this regard, hydrogen bonding interaction has shown a much stronger effect compared to other interactions. In order to induce hydrogen bonding interaction, the filler surface is commonly modified by various modifiers. In the present work, instead of filler surface modification, we introduce ZnSn(OH)6 filler (hydroxide filler having a high number of –OH groups) into the PVDF matrix in order to facilitate the hydrogen bonding interaction. Not only the hydroxide fillers but the effect of wide particle size variation (from nano to micrometer range) into PVDF has also been shown here for the very first time. ZnSn(OH)6 fillers with similar morphology but different sizes have been synthesized by using a variety of techniques and then incorporated into the PVDF matrix. The microstructural defects of the composite films have been found to be gradually increased with the increase in filler size which in turn caused to gradually increase their space charge polarization. Filler, with 915 nm size has shown the best polar phase formation (∼84 %), dielectric permittivity (∼10 at 1 kHz), and piezoelectric energy harvesting performance (output voltage ∼20 V) of the resulting PVDF-based composite and hence has been used for various real-life applications. All of these results have been suitably explained here on the basis of interfacial interaction, microstructural defect, and the mechanism of formation of space charge polarization.

Effect of retained austenite on the fatigue behavior of modified bainitic 100Cr6 steels considering local phase transformation

Since highly loaded components, such as roller bearings, tend to have relatively high lifetime scatter caused by microstructural defects, an increased defect tolerance of the material can improve the performance as well as the reliability of these highly stressed components. To increase the defect tolerance of the roller bearing steel 100Cr6, two different laboratory melts with either 1.5 wt.-% Al or 1.5 wt.-% Si in addition to the standard composition were developed. After an adapted heat treatment, both steels exhibited a bainitic microstructure with a relatively high content of retained austenite with more than 20 vol.-%. Considering the effects of the retained austenite, a defined mechanical stability is essential to avoid excessive deformation-induced transformation from the retained austenite into α′-martensite, which can lead to shape deviations in components. However, besides the increased deformability of the austenitic phase, local phase transformations in the vicinity of defects can increase the defect tolerance. The fatigue tests performed at ambient temperature (AT) and at T = 100 °C, show a higher fatigue strength of the Si-alloyed steel due to a refined microstructure and revealed for both steels a relatively high austenite stability, since no macroscopic phase transformation was observed. The high austenite stability can be explained by a relatively high carbon content of the austenitic phase. However, in contrast to the Al-alloyed steel, a decrease in the fatigue strength and in the defect tolerance due to the increased temperature were observed for the Si-alloyed steel, which indicates a more pronounced phase transformation at AT. The lower carbon content and the finer distribution of the retained austenite, when compared to the Al-alloyed steel, are supposed to be the reason. While a smaller carbon content decreases the phase stability, the refined austenite distribution results in a higher probability of retained austenite presence in the vicinity of a defect.

Functional Epicardial Conduction Disturbances Due to a SCN5A Variant Associated With Brugada Syndrome

BackgroundBrugada syndrome is a significant cause of sudden cardiac death (SCD), but the underlying mechanisms remain hypothetical. ObjectivesThis study aimed to elucidate this knowledge gap through detailed ex vivo human heart studies. MethodsA heart was obtained from a 15-year-old adolescent boy with normal electrocardiogram who experienced SCD. Postmortem genotyping was performed, and clinical examinations were done on first-degree relatives. The right ventricle was optically mapped, followed by high-field magnetic resonance imaging and histology. Connexin-43 and NaV1.5 were localized by immunofluorescence, and RNA and protein expression levels were studied. HEK-293 cell surface biotinylation assays were performed to examine NaV1.5 trafficking. ResultsA Brugada-related SCD diagnosis was established for the donor because of a SCN5A Brugada-related variant (p.D356N) inherited from his mother, together with a concomitant NKX2.5 variant of unknown significance. Optical mapping demonstrated a localized epicardial region of impaired conduction near the outflow tract, in the absence of repolarization alterations and microstructural defects, leading to conduction blocks and figure-of-8 patterns. NaV1.5 and connexin-43 localizations were normal in this region, consistent with the finding that the p.D356N variant does not affect the trafficking, nor the expression of NaV1.5. Trends of decreased NaV1.5, connexin-43, and desmoglein-2 protein levels were noted; however, the RT-qPCR results suggested that the NKX2-5 variant was unlikely to be involved. ConclusionsThis study demonstrates for the first time that SCD associated with a Brugada-SCN5A variant can be caused by localized functionally, not structurally, impaired conduction.

Flexible and mechanically strong MXene/cellulose-lamellae sheets for electromagnetic interference shielding

MXene, two-dimensional layered transition metal carbides, nitride, or carbonitrides, have shown promise for ultrahigh electromagnetic interference (EMI) shielding in flexible electronics and aerospace due to their intrinsic metallic conductivity and mechanical strength. However, weak interfacial interactions, void microstructure defects, and oxidative degradation can leave MXene sheets in a thermodynamically metastable state, resulting in poor EMI shielding and mechanical strength. Herein, we utilized abundant hydrogen-bonded ultrafine cellulose lamella (UCL) to sequentially bridging induced densification of MXene nanosheets. This resulted in improved the tensile strength, toughness, oxidative stability, resistance to ultrasonic decomposition, and super-foldable conductivity of MXene sheets. The resulting MXene@UCL sheets (MXCS) exhibited high electrical conductivity of up to 7649 S cm−1 and ultrahigh weight-normalized shielding efficiency (SSE/t, 53003.45 dB∙cm2 g−1), making them mechanically strong and highly conductive. The MXCS material has a tensile modulus of up to 10.9 ± 0.7 GPa and provides excellent weight-normalized shielding efficiency. Simultaneously, it is capable of enduring 100,000 repetitions of folding without experiencing any damage to its construction or fluctuations in conductivity. Furthermore, high-strength scalable MXCS sheets can be produced using doctor blade casting, commercial resin bonding, and aerogel calendering methods, without compromising their performance. This has significant scientific and practical application potential.

Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by high-pressure torsion using positron annihilation spectroscopy and a high resolution X-ray diffraction

Two MgRE (RE = Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DB-VEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ∼115 nm for the as-received state to ∼207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations (positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4–6 × 1014 m−2).

(Invited) Application of Synchrotron X-Ray Topography Techniques to the Analysis of Defect Microstructures in Bulk GaN Substrates and Epilayers for Power Devices

The study of defects and strain in GaN substrates and epilayers for vertical device development using synchrotron X-ray topography techniques is presented. Synchrotron monochromatic beam X-ray topography (SMBXT) studies show that ammonothermal-grown GaN substrate wafers have the lowest dislocation densities while patterned hydride vapor phase epitaxy (HVPE) GaN reveal a starkly heterogeneous distribution of dislocations with large areas containing low threading dislocation densities and HVPE GaN substrates contain high dislocation densities. Epitaxial growth does not nucleate new defects but interactions of dislocations with point defects can cause changes in dislocation configurations. Rocking curve Analysis by Dynamical Simulation (RADS) is shown to be effective in analysis of implantation by correlating the depth profile of strain with the doping profile. Removal of lattice damage induced by implantation requires annealing with proper capping or under high pressures to limit loss of material and lattice distortion. Inductively coupled plasma (ICP) etching may introduce strain in GaN material that can be partially recovered by TBCl etching. Diffusion doping does not introduce new strains in GaN material while neutron transmutation doping at low levels can lead to curing of defects while higher levels lead to irradiation damage and nucleation of new defects.

Defect microstructure of a Ti64 alloy under TI2+ ion irradiation. Influence of dose and temperature

The present paper focuses on the microstructural changes in Ti64 alloy after irradiation. The titanium alloys allow a significant decrease in activation and mass with a similar mechanical strength and a similar corrosion resistance than 304 stainless steels, widely used for core internal structures of Pressurized Water Reactors. The use of titanium alloys could be therefore a significant improvement for reactor exploitation and decommissioning. The nature, size and density of the radiation-induced defects are likely to be important parameters governing the in-reactor behavior of the material. The aim of the study was to devise new achievements in thin foil preparation and Transmission Electron Microscopy (TEM) imaging in order to accurately identify and quantify the Ti64 irradiation defects, at temperatures representative of irradiation temperatures in a reactor. The method to image and count the precipitates was developed with samples irradiated by ions at the temperature of 600 °C. Indeed, the microstructure of the sample irradiated at 600 °C was characterized by a low density of tangled dislocations, and big precipitates, that were easily evidenced. Then the process was applied in samples irradiated with ions at 430 °C and 300 °C characterized by a microstructure of tangled dislocations, loops and small precipitates. In 430 °C irradiation condition, the measurement in dark field with a B∼[11–23]α orientation and with a high magnification micrograph provided similar results than Atom Probe Tomography (APT) analyses. In irradiation condition at 300 °C, the precipitates were imaged by TEM as soon as the dose of 1 dpa. However they were not observed at the dose of 0.4 dpa. The precipitates were so small and their density was so high that the measurement by TEM was very imprecise and APT analyses were needed. The results of this microstructural analysis allowed a discussion on the nucleation mechanism of the irradiation defects in Ti64 alloy.

Introducing field evaporation energy loss spectroscopy

Retrieving information on the chemical and bonding states of atoms in a material in three-dimensions is challenging even for the most advanced imaging techniques. Here, we demonstrate that this information is accessible via straight-flight-path atom probe tomography experimental data, however it requires additional processing. Using an activation energy model that involves linear field dependance, and complementing it with DFT simulations, we extract the ion energy loss related to the kinetics of the field evaporation process from the mass peak shape. In turn, we reconstruct how evaporated atoms were originally bound to the surface. We name our data processing approach evaporation energy loss spectroscopy (FEELS), and showcase its application by analyzing microstructural features and defects in an array of metallic materials. Finally, we discuss the general applicability of FEELS to any atom probe data set.

Effect of equal-channel angular pressing on ordering kinetics and twinning in an 18-carat AuCuAg alloy

The ability to modify microstructural features and the resulting properties of red gold provides an attractive potential for applications in electronics, dental devices or jewelry. In this study, the effect of severe plastic deformation by equal-channel angular pressing (ECAP) on microstructural evolution in an 18-carat AuCuAg alloy, and on the ordering kinetics during subsequent aging, is investigated. Differential scanning calorimetry measurements show that the ordering process is significantly influenced by a plastically deformed microstructure and lattice defects introduced by one or two passes of ECAP. Electron backscatter diffraction and transmission electron microscopy demonstrate that the microstructural evolution during ordering, accompanied by the formation of an L10 superstructure, substantially depends on the thermo-(mechanical) history of the material: While the undeformed material clearly shows a hierarchical structure of twins on different length scales, only a few nanotwins are observed within the strongly deformed microstructures after ECAP. Moreover, after ECAP, static recrystallization is considerably suppressed during long-term annealing at elevated temperatures close to the phase transition temperature. These results clearly highlight the potential of ECAP in combination with heat treatments for microstructural optimization of AuCuAg alloys and their applications.

In-situ SEM study on fatigue crack behavior of a nickel-based single crystal alloy at 950 °C and 1050 °C

As the blade material of engine, nickel-base single crystal superalloy has been subjected to complex service environment such as high temperature and alternating load for a long time. In this work, the mechanism of fatigue microcrack initiation and propagation in a nickel-based single crystal at 950 °C and 1050 °C was studied by using the in-situ scanning electron microscope high temperature fatigue test system. At 950 °C, the alloy deformation was controlled by slip and the crack shear γ/γ’ phase cracking, showing Stage I mode. At 1050 °C, the alloy crack tearing occurred at the γ phase parallel to the loading direction and γ/γ' interface perpendicular to the loading direction and presents a Stage II mode perpendicular to the loading axis, then changes into Stage I in the accelerating stage. The deformation mechanism of fatigue cracking at two temperatures was compared. Besides, the influence of the microstructure defects on the fatigue crack behavior was discussed. The results show that the propagation of the microcrack below 100 μm shows evident fluctuations, which is closely related to the microstructure and the development stage of the fatigue crack.

Interaction of compression failure mechanisms in composites with ply waviness defects

This article presents results from experimental and computational investigations of composite laminates with embedded ply waviness defects of different geometries under compression. The effect of the ply waviness defect on the initiation, interaction, and evolution of failure mechanisms of surrounding plies are studied. Using high-resolution imaging and digital correlation analysis, the strain localization phenomenon is monitored, and the sequence of failure mechanisms is established. The experimental observations are supported with computational finite element progressive failure analyses of the same composites with ply waviness defects using an energy based continuum damage mechanics approach. For the case of laminates with ply waviness defects of high angles, a delamination crack between the wavy plies and adjacent transverse plies is the dominant mode of failure, which interacts strongly with the fiber compression and matrix tension modes. For the case of laminates with ply waviness defects of low angles, failure does not initiate at the waviness defect but at locations where the laminate strength was locally reduced due to other microstructural defects. The combined experimental and computational analyses presented here advanced the understanding of the interaction of compression failure mechanisms in composites with ply waviness defects, which is highly challenging to experimentally measure.

EVOLUTION AND DISTRIBUTION OF SHAKES IN LARCH LOGS DURING AIR DRYING

This paper analyzed the length, width, and location of shakes in the air-drying process of larch log (Larix principis-rupprechtii Mayr) 1 m long and 66% initial moisture content. The development law and distribution characteristics of shakes during log drying of larch were studied and shake generation and development law were analyzed from two aspects of microstructure and growth defects. The variation of dry shrinkage deformation along the radial direction and knot influence on it was analyzed using the split-shaped stress test strips. At the cellular level, the cell wall shrinkage behavior of heartwood and sapwood and the microstructure of knots were observed. The results showed a significant relationship between eccentricity and shake distribution; the IIa region is the most prone to dry shake. The evolution of shakes is closely related to the drying rate. In the high-speed drying stage (MC ≥ 40%), shakes almost do not occur; in the decelerating drying stage (40% ≥ MC ≥ 20%), the amount, length, and width of shakes increase rapidly. In the low-speed drying stage (20% ≥MC), the area of shakes tends to stabilize or even decline. The main reasons for dry shaking are the dry shrinkage difference between tangential and radial cell walls, early and late wood, heartwood and sapwood, and moisture content gradient during the drying process.

Effect of particle size on the microstructure and consolidation behavior of nickel coating fabricated by laser shockwave sintering

Nickel powders of nominal sizes (i.e., 50 nm, 300 nm, and 2 μm) were pre-coated on copper substrates and then subjected to laser shock processing (LSP) for producing nickel coating. The shockwave consolidation behavior, microstructure, and bonding performance were investigated as a function of particle size. Results indicated that nano-coating had better surface quality, decreased microstructural defects (pores and cracks), and higher bonding strength (approximately twice the hardness value) than its micro-counterpart. Microstructure analysis revealed that nano/submicron particles were consolidated by a mixed solid-liquid sintering behavior, whereas micron particles were consolidated only by solid-state sintering under laser shock. A mixed microstructure of nanocoating was obtained, consisting of solid-state atomic bonds between solid-state sintered particles and amorphous phases between liquid-phase sintered particles. After LSP, the cold shock characteristics of LSP could not only reduce the overall grain growth and oxidation of nano coating, but also induce fine nanocrystalline at the inter-particle interface of the micron coating by dynamic recrystallization.

Deuterium retention in tungsten, tungsten carbide and tungsten-ditungsten carbide composites

The selection of the most suitable material for the EU DEMO divertor is still underway. Current research focuses on the development of tungsten-based materials for plasma-facing applications. In addition to other requirements, the candidate material must also exhibit low intrinsic hydrogen isotope retention. To verify the suitability of the tungsten carbide-containing materials, we examined the effect of carbon in the form of carbide or free carbon on deuterium (D) retention.The samples were consolidated by Field Assisted Sintering (FAST) and examined in terms of phase composition and microstructure before the d-retention studies. The Nuclear Reaction Analysis (NRA) technique was used to determine the depth distribution of D after the exposure to D plasma (fluence of 1.3 × 1024 D/m2 and 1.3 × 1025 D/m2 and an exposure temperature of 370 K and 523 K, respectively). Thermal Desorption Spectroscopy (TDS) was used to measure the D desorption spectra. The surfaces of samples exposed to D plasma were also examined in terms of microstructure by scanning electron microscopy. The study has shown that apart from the d-fluence and exposure temperature, the materials’ composition plays a vital role in d-retention, accompanied by blisters and pillar formation. The lowest d-retention was observed for tungsten and the highest in the W-W2C composite. The blisters and pillars were formed in these two materials but not in the WC, which also contains free carbon. At higher D fluence, approximately 15 to 20-times more blisters and pillars were formed in the W-W2C composite than in the tungsten prepared by the same method. The results suggest that the number of defects causing higher d-retention is the highest in W-W2C. On the other hand, the absence of surface irregularities in the WC-C sample after D retention studies indicates that the cause for higher D retention does not lie in the carbides, but, presumably, the microstructural and crystal lattice defects govern the D retention in tungsten-tungsten carbide systems.

Defect elimination and microstructure improvement of laser powder bed fusion β-solidifying γ-TiAl alloys via circular beam oscillation technology

To eliminate metallurgical defects and improve microstructures in laser powder bed fusion (LPBF) β-solidifying γ-TiAl alloys, circular beam oscillation technology was used to fabricate a Ti–43Al–9V-0.5Y alloy in this work. The metallurgical defects and microstructures under conventional linear (non-oscillating) scanning and circular oscillating scanning are first studied in comparison. Then, the microstructural evolution and defect suppression mechanisms under circular oscillating scanning are revealed based on the melt flow behavior. In contrast to the non-oscillating scanning, circular oscillating scanning can better eliminate the pores and cracks of LPBFed Ti–43Al–9V-0.5Y alloy. As the oscillating velocity is decreased, the crack density decreases and the microstructure changes from columnar to equiaxed grains. The crack-free samples with a relative density of 99.98% and fine equiaxed grains are obtained as the oscillating velocity is less than or equal to 100 mm/s. The microhardness (473–581 Hv) of the non-oscillating samples is higher than that (440–487 Hv) of the oscillating samples. The room-temperature compressive strengths (∼1222 MPa and ∼1931 MPa) and tensile strength (∼253 MPa) of the crack-free oscillating LPBFed samples are superior to those of the as-cast counterparts. The suppression of pores is ascribed to the improved keyhole stability, enhanced melt convection as well as escape of bubbles under circular beam oscillation. When the oscillating velocity is less than or equal to 100 mm/s, the sufficient stirring effect of the laser beam promotes the formation of fine equiaxed grains and the reduction of brittle B2 phase content, which effectively inhibits cracking.