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In the present paper, the microstructural evolution and tensile properties of additively manufactured stainless steel CX were investigated. Using scanning electron microscope (SEM), several powder particle morphologies were identified in the stainless s steel CX feedstock powder where the spherical morphology was found to be the dominant one. In addition, X-ray diffraction (XRD) technique detected austenite and martensite phases in both stainless steel CX powder and as-built sample, whereas no carbide peak appeared on the XRD patterns. Moreover, lath or needle-like martensite phase was observed in the microstructure of the as-built sample. The level of porosity was very low in the as-built sample, indicating the manufacturing of a nearly fully dense sample. Furthermore, a high ultimate tensile strength together with a good elongation to fracture was obtained for the horizontally-built stainless steel CX sample. Finally, examination of the fracture surfaces after tensile tests confirmed the ductile failure mode of the samples, in which the pull-out of the scan tracks and coalescence of the voids resulted in the tear and final rupture. This study demonstrates the successful additive manufacturing of stainless steel CX with outstanding tensile properties. [ABSTRACT FROM AUTHOR]

ABSTRACT This research studies the effect of variable stress levels on the rotating bending fatigue (RBF) tests of 316L stainless steel fabricated by the laser powder bed fusion (LPBF) method. The mechanical properties and fatigue behavior were evaluated to ascertain the correlation between the applied stress levels and microstructural changes that occurred during the fatigue experiments. These relationships were further investigated using a classical model developed on the Python platform. The microstructural analysis demonstrated that the face‐centered cubic structure was maintained throughout the application of stresses, varying from 255 to 402 MPa along with no phase changes. Nevertheless, the density of shear lines on the surface was substantially influenced by variations in stress levels as demonstrated by high‐stress areas in Kernel average misorientation maps. At lower stress levels, the model analysis exhibited a higher degree of reliability, with R2 values of 96.25% at lower stress rather than 89.30% at higher stress. [ABSTRACT FROM AUTHOR]

Abstract Microstructure of deformed DMLS-AlSi10Mg under quasi-static loading was studied using TEM to elaborate the strengthening mechanisms. In addition to Orowan (due to presence of Si precipitates), Hall-Petch (due to eutectic Si walls), and dislocation hardening (due to pre-existing entangled dislocations) mechanisms, Mg 2 Si precipitates (colonies) contributed to the strength of alloy by impeding dislocation motion. The level of this contribution was evaluated as ~13 MPa by comparing the modeled and measured yield strength. [ABSTRACT FROM AUTHOR]

The fabrication process, sintering cycles through two sintering methods, microstructural and texture characterization, mechanical properties, and electrical conductivity of metal paste-deposited copper parts were investigated in this study. In the first condition, samples were air-debinded for carbon content removal followed by a sintering cycle. A sintering profile with the maximum sintering temperature and time of 1080 °C and 1 hr. was implemented after performing the air-debinding cycle at 250 °C for 2 hrs. In the second condition, samples were sintered in the environment of copper oxide for carbon removal in the early stages of the sintering cycle, i.e., 1070 °C for 1 hr and 1080 °C for 1, 2, and 3 hrs. The microstructural observations revealed coarser grains in the air-debinded samples, perhaps due to additional generated heat during carbon oxide formation, which may produce destructive effects on the boundary (HAGBs, twins, and CSL) volume and densification behavior of copper parts. However, through the second method, much finer grains and higher densities of boundaries were detected in the microstructure. Despite the significant effect of sintering conditions on the microstructure, texture interpretations revealed minor changes in the pole figures for different situations. Using the second sintering method and owing to the less carbon content and based on the density of the boundaries and their configurations, higher electrical conductivity (98.4±1.3 % IACS) was recorded by sintering the green parts. The comparison between the data from this study with other parts printed through other additive manufacturing techniques demonstrated a superior electrical conductivity level and acceptable balance between strain and strain notably with the sample sintered for 3 hrs. [Display omitted] • The presence of CuO improved electrical conductivity by decreasing carbon content. • Superior mechanical properties from increased sintering time and temperature. • Higher boundary density measured in CuO-assisted samples. • High porosity level observed in air-debinded samples owing to high carbon content. [ABSTRACT FROM AUTHOR]

• Unveiling rotating bending corrosion fatigue behavior of laser powder bed fused 316L. • Proposing a fatigue life prediction model with high accuracy (less than 10% deviation). • Quantifying pitting defect/microstructure influence on corrosion fatigue performance. • Comparing the stress-life response of pre-corroded and non-corroded AM 316L. In this study, the ex-situ rotating bending corrosion fatigue behavior of laser powder bed fused stainless steel (SS) 316L has been studied incorporating experimental analyses and modeling. The findings revealed significant variations (almost 20 %) in fatigue lifetime in pre-corroded specimens relative to non-corroded (virgin) specimens because of corrosion-derived pitting phenomena on the surface. To this end, the fatigue strength of virgin (non-corroded) and pre-corroded SS 316L were recorded at 242 MPa and 203 MPa, respectively. Upon conducting the fatigue tests and extracting stress-life trends, advanced microstructural characterization and postmortem analyses were used to quantify fatigue crack behavior and fracture surface. An empirical model is also developed employing depth-sensing indentation testing, linear elastic fracture mechanics, and computer tomography scans to propose an optimum predictive trend. The analysis comparing existing models with our proposed model demonstrates reasonable agreement between experimental findings and the predicted life for the studied laser powder bed fused SS 316L material exposed to corrosion rotating bending fatigue test. The findings of this research carry important contributions to the structural integrity and longevity of marine engineering, ship construction, naval operations, and naval aviation where materials and components are exposed to cyclic loading and corrosion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pure copper electrodes were produced by the laser powder bed fusion technique. • The microstructure of the part was examined in different areas. • The effect of the thermal history on the porosity percentage was studied through the height. • The electrical and thermal properties of the additively manufactured parts were compared to the original cast part. • Additively manufactured pure copper electrode corrosion in two different environments was evaluated. This study explores the fabrication and characterization of a pure copper electrode for an EDM equipment using laser powder bed fusion (LPBF) and comparing its performance with an original cast sample. The microstructural, mechanical, electrical, thermal, and corrosion characteristics of the samples were analyzed. The microstructure of the additively manufactured (AM) sample exhibited superior mechanical properties, with an 18 % increase in ultimate tensile strength and more than two times greater elongation in comparison with those of the cast sample. Moreover, the electrical and thermal conductivity coefficients of the AM sample were found to be consistent with industry standards as 5.52 × 107 S/m and 361 W/mK, respectively. Additionally, the potentiodynamic polarization corrosion test results of the AM sample further exhibited superior corrosion resistance in terms of the corrosion potential particularly in a 3.5 % NaCl environment. Advanced electron microscopy techniques were used to investigate the differences in the properties of the AM and cast samples and further shed light on the superior properties of the LPBF counterpart. Despite challenges in manufacturing pure copper components through LPBF, this study demonstrates the feasibility of producing a functional part that competes effectively with cast counterparts and excels in certain aspects. [ABSTRACT FROM AUTHOR]

Abstract Rod shaped samples of AlSi10Mg alloy were additively manufactured in vertical and horizontal directions using direct metal laser sintering technique and subjected to dynamic loading using Split Hopkinson Pressure Bar apparatus at a strain rate of 1400 s−1. Despite employing the same process parameters to fabricate the samples in two directions, the as-built samples possessed different microstructures, where columnar and equiaxed microstructures were developed in the vertical and horizontal samples, respectively. Moreover, fine and coherent Si precipitates were observed in the vertical sample while coarse and semi-coherent ones were developed in the horizontal sample. In addition, changing the building direction from horizontal to vertical led to a three-fold increase in dislocation density. After applying the compressive impact loads on the vertical and horizontal samples, it was found that the dynamic loading behavior of the two samples was almost similar despite the crucial differences in the initial microstructures. The microstructural analysis of the deformed samples revealed entangled networks of dislocations. In addition, over some locations, low angle grain boundaries developed due to partial dynamic recovery. The strengthening behaviors of the two samples additively manufactured in vertical and horizontal directions were investigated using the fundamentals of alloy hardening to unveil the similarities. Graphical abstract Unlabelled Image Highlights • Rod samples of AlSi10Mg additively manufactured in horizontal and vertical directions through DMLS using same parameters • Microstructure of as-built samples were different in terms of cell structure, pre-existing dislocations and Si precipitates • The samples were subjected to high strain rate compressive deformation using Split Hopkinson Pressure Bar apparatus • Deformed microstructure consisted entangled dislocation networks along with low angle grain boundaries due to partial DRV • Strengthening behavior of the samples was analyzed considering Orowan, Hall-Petch and dislocation hardening mechanisms [ABSTRACT FROM AUTHOR]

Additive manufacturing of reactive metals has opened door to consider using metal 3D printing to manufacture aluminum alloys for different applications from automotive and aerospace to defense. However, one of the major milestones of adopting the technology is still the high price of metal powder in comparison to casting methods. Using recycled powder to additively manufacture parts can be considered one way to decrease the final price in this technology. In the present paper, the microstructural evolution and mechanical properties of the DMLS-AlSi10Mg_200C alloy manufactured by recycled powder were investigated. As the first step of this research, the powder characteristics, i.e. morphology, average particle size, microstructure and composition, of virgin, condensate and recycled AlSi10Mg powder were studied. It was inferred that virgin and recycled powders had comparable powder characteristics, which are very different in comparison to the condensate powder. In the second step of this research, microstructural and mechanical characterization of the as-built DMLS-AlSi10Mg_200C alloy using recycled powder revealed that elongation of horizontally built DMLS-AlSi10Mg_200C was higher compared to that of vertically built. In addition, the fracture surfaces of vertically and horizontally built samples were investigated and possible fracture modes discussed. It is confirmed that, the microstructure and mechanical behavior of the as-built as-built DMLS-AlSi10Mg_200C manufactured by recycled powder were similar to that of virgin powder. [ABSTRACT FROM AUTHOR]

Indentation hardness (H i n ) and strain rate sensitivity (SRS) of additive manufactured Ti–6Al–4V (Ti64) alloys fabricated through both laser powder bed fusion (L-PBF) and electron beam melting (EBM) are investigated. One major difference between these processes is the higher cooling rates associated with the L-PBF. The indentation tests were performed at loading rates of 1, 10, and 50 mN/s. The L-PBF alloy showed a higher hardness value (3.45 GPa at 1 mN/s, 3.57 GPa at 10 mN/s, and 3.66 GPa at 50 mN/s) being correlated with its finer grain structure as compared with the EBM counter material (3.12 GPa at 1 mN/s, 3.37 GPa at 10 mN/s, and 3.55 GPa at 50 mN/s). The indentation SRS was explained based on the print orientation and dislocation density. EBM-Ti64 shows a higher SRS (0.0335 compared with 0.0147 in the L-PBF alloy) due to the rotation of α-prismatic planes along the building direction. • L-PBF and EBM techniques were used to fabricate Ti64 samples • EBSD was employed to study the microstructure of the alloys • The rate-dependent micromechanical properties of the samples were evaluated using nanoindentation • The strain rate sensitivity of the alloys was correlated to the microstructure and texture [ABSTRACT FROM AUTHOR]

Several core–shell nanosphere chains were observed in the electron beam melted Ti–48Al–2Cr–2Nb samples. The formation mechanism of such core–shell nanospheres, induced by Al vaporization, during the electron beam melting of γ-TiAl was investigated using the HRTEM, FESEM, STEM, and XRD analyses. The solidification of TiAl/Ti 3 Al lamellae, in the vicinity of the Al-diminished zones, was disclosed by microstructural studies. The core and shell of the nanospheres were characterized as porous Al and α-Al 2 O 3 , respectively. Finally, the formation of core–shell nanosphere chains in the additive manufactured γ-TiAl was schematically illustrated. [Display omitted] • γ-TiAl intermetallic samples were fabricated by electron beam melting (EBM) process. • Formation mechanism of core–shell nanosphere chains during EBM was investigated. • Core and shell of the nanospheres were characterized as Al and Al 2 O 3 , respectively. • Microstructural alteration during the EBM of γ-TiAl was schematically illustrated. [ABSTRACT FROM AUTHOR]

To restore defected AA2618 alloy molds, remanufacturing of the damaged areas using AlSi10Mg alloy through laser powder bed fusion (L-PBF) technique is proposed. This study in particular focuses on the corrosion characteristics of the fabricated L -PBF AlSi10Mg / cast AA2618 bimetal structure in aerated 3.5 wt.% NaCl electrolyte with respect to the individual alloys. The L -PBF AlSi10Mg side of the bimetal sample was characterized with a superior corrosion response and the highest passive film stability compared with the cast AA2618 side and the dissimilar sample (prepared from the interface region), ascribed to its homogeneous microstructure, containing a very fine network of eutectic Si embedded in a fine grained and supersaturated α-Al matrix. The overall corrosion performance of the dissimilar sample was found to be between the cast AA2618 and L -PBF AlSi10Mg part, with no sign of macro-galvanic corrosion effect between the dissimilar alloys. The heavily precipitated microstructure of the cast AA2618 alloy, particularly the anodic Al 2 CuMg phase and cathodic Fe-containing intermetallics versus the Al-matrix, dictated the inferior corrosion properties of the cast sample and the cast side of the dissimilar sample. [ABSTRACT FROM AUTHOR]

This paper presents a study that aims to modify the interfacial characteristics of maraging steel-H13 bimetal structures through heat treatment procedures. Laser powder bed fusion (LPBF) was used to deposit maraging steel powder (MS1) on H13 hot work tool steel blocks. Subsequently, printed samples went through two different treatment cycles: (i) solution treatment, and (ii) aging treatment recommended for maraging steel. The microstructure, grain morphology, and mechanical response of MS1-H13 bimetals were assessed and compared with the as-built condition. Scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) techniques were used to analyze the interfacial modification upon heat treatment. Using uniaxial tensile testing and microhardness measurements along with 2D nanoindentation mapping, the mechanical properties of bimetal structures were correlated to the microstructural evolution of the samples during different heat treatments. Although the aging treatment was not effective to induce tangible microstructure changes, the solution treatment succeeded in the modification of MS1-H13 interface. A fully lath martensitic morphology was promoted across the interface, eliminating microstructure and hardness inhomogeneity as well as interface distinction between both sides. Finally, the solution treatment enhanced the mechanical properties of MS1-H13 bimetal structure by tripling the ultimate tensile strength. • MS1-H13 bimetallic structures were fabricated using laser powder bed fusion. • Aging and solution heat treatment cycles were carried out on the bimetals. • Microstructural modification occurred across the interface upon heat treatments. • Uniform microstructure in terms of grain morphology and crystal structure was formed. • Remarkable strengthening was observed in the solution treated samples. [ABSTRACT FROM AUTHOR]

In this work, the effect of built direction on the small-scale mechanical properties and microstructure of a novel maraging stainless steel (SS-CX) manufactured through the selective laser melting (SLM) process was studied. Advanced electron microscopy and nanoindentation techniques were utilized to evaluate retained austenite fraction and micro-mechanical properties, respectively. Different thermal histories caused by the change of the built direction resulted in microstructures with different volume fractions of retained austenite and grain morphology. Furthermore, the slower cooling rates in the vertically built sample was found to result in the formation of large elongated grains and lower hardness values during the nanoindentation experiments. • The building direction changes the microstructure of selective laser melting product. • Changing the building direction resulted in different volume fractions of retained austenite. • The thermal history of the product depends on the printing orientation. • The laser scan path changes the static and dynamic recovery processes. [ABSTRACT FROM AUTHOR]

• Maraging steel microlattice was printed by SLM, crushed, and simulated using FEM. • SEM and micro-CT was performed on as-built samples to verify structural integrity. • Two modeling techniques are presented based on as-built and as-designed geometries. • FESEM was performed on the crushed lattice for failure analysis. • Good agreement is found between the experiment and the simulations. Additive metal manufacturing techniques, in particular laser-based powder bed fusion methods, are revolutionary in their capabilities to fabricating new classes of lightweight and complex materials called metallic microlattices. In this paper, a microlattice structure was designed for energy absorption purposes and further additively manufactured using maraging steel (Maraging300) powder through Laser-powder bed fusion (L-PBF) technique. In addition, several cylindrical bars and cubes in horizontal and vertical directions were manufactured to perform uniaxial tensile and compression tests on bulk L-PBF Maraging300. The manufactured microlattices were characterized using different electron microscopy techniques including scanning electron microscopy and micro-CT analysis to ensure that the desired structural integrity was achieved. In addition, the microlattice was then crushed using a universal mechanical testing machine to evaluate its performance experimentally under quasi-static uniaxial compressive loading conditions. Along with the crush, a nonlinear finite element model with predictive capabilities was then developed using commercial package (LS-DYNA) for axial crush of the microlattice to compare its expected performance. Two finite element models are developed using the as-built geometry from the printed lattice, and the as-designed geometry. The effect of model parameters is discussed and very good agreement between the experimental results and the finite element prediction was observed. Finally statistical analysis of the model and failure analysis of the crushed lattice is presented. [ABSTRACT FROM AUTHOR]